Renewable Polymers E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 654

Veröffentlichungsjahr: 2011

Beschreibung

Presents the synthesis, technology and processing details of a large range of polymers derived from renewable resources It has been a long-term desire to replace polymers from fossil fuels with the more environmentally friendly polymers generated from renewable resources. Now, with the recent advancements in synthesis technologies and the finding of new functional monomers, research in this field has shown strong potential in generating better property polymers from renewable resources. A text describing these advances in synthesis, processing, and technology of such polymers not only provides the state-of-the-art information to researchers, but also acts to stimulate research in this direction. The contents are based on a wide range of functional monomers and the contributions are written by eminent researchers. Specifically Renewable Polymers: * Demonstrates the design, synthesis, properties and applications of plant oil-based polymers * Presents an elaborate review of acid mediated polymerization techniques for the generation of green polymers * Details the production of polyhydroxyalkanoates (PHA) from olive oil based wastewater * Describes the use of atom transfer radical polymerization (ATRP) techniques * Reviews the renewable polymers derived from transgenic crop plants * Provides an overview of a range of biomass-based polymers * Concludes with the recent efforts and approaches exploiting the natural materials in developing drug delivery systems.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Preface

List of Contributors

Chapter 1: Polymers from Renewable Resources

1.1 Introduction

1.2 Naturally Renewable Methylene Butyrolactones

1.3 Renewable Rosin Acid-Degradable Caprolactone Block Copolymers

1.4 Plant Oils as Platform Chemicals for Polymer Synthesis

1.5 Biosourced Stereocontrolled Polytriazoles

1.6 Polymers from Naturally Occurring Monoterpene

1.7 Polymerization of Biosourced 2-(Methacryloyloxy) ethyl Tiglate

1.8 Oxypropylation of Rapeseed Cake Residue

1.9 Copolymerization of Naturally Occurring Limonene

1.10 Polymerization of Lactides

1.11 Nanocomposites Using Renewable Polymers

1.12 Castor Oil Based Thermosets

References

Chapter 2: Design, Synthesis, Property, and Application of Plant Oil Polymers

2.1 Introduction

2.2 Triglyceride Polymers

2.3 Summary

References

Chapter 3: Advances in Acid Mediated Polymerizations

3.1 Introduction

3.2 Problems Inherent to Cationic Olefin Polymerization

3.3 Progress Toward Cleaner Cationic Polymerizations

3.4 Environmental Benefits via New Process Conditions

3.5 Cationic Polymerization of Monomers Derived from Renewable Resources

3.6 Sustainable Synthesis of Monomers for Cationic Polymerization

References

Chapter 4: Olive Oil Wastewater as a Renewable Resource for Production of Polyhydroxyalkanoates

4.1 Polyhydroxyalkanoates (PHAs): Structure, Properties, and Applications

4.2 PHA Production Processes Employing Pure Microbial Cultures

4.3 PHA Production Processes Employing Mixed Microbial Cultures

4.4 Olive Oil Mill Effluents (OMEs) as a Possible Feedstock for PHA Production

4.5 OMEs as Feedstock for PHA Production

4.6 Concluding Remarks

References

Chapter 5: Atom Transfer Radical Polymerization (ATRP) for Production of Polymers from Renewable Resources

5.1 Introduction

5.2 Atom Transfer Radical Polymerization (ATRP)

5.3 Synthetic Strategies to Develop Functional Material Based on Renewable Resources Composition, Topologies and Functionalities

5.4 Sustainable Sources for Monomers with a Potential for Making Novel Renewable Polymers

5.5 Conclusions and Outlook

References

Chapter 6: Renewable Polymers in Transgenic Crop Plants

6.1 Natural Plant Polymers

6.2 De Novo Synthesis of Polymers in Plants

6.3 Conclusion

References

Chapter 7: Polyesters, Polycarbonates and Polyamides Based on Renewable Resources

7.1 Introduction

7.2 Biomass-Based Monomers

7.3 Polyesters Based on Renewable Resources

7.4 Polycarbonates Based on Renewable Resources

7.5 Polyamides Based on Renewable Resources

7.6 Conclusions

References

Chapter 8: Succinic Acid: Synthesis of Biobased Polymers from Renewable Resources

8.1 Introduction

8.2 Polymerization

8.3 Conclusions

References

Chapter 9: 5-Hydroxymethylfurfural Based Polymers

9.1 Introduction

9.2 5-Hydroxymethylfurfural

9.3 5-Hydroxymethylfurfural Derivatives

9.4 Polymers from 5-Hydroxymethylfurfural Derivatives

9.5 Conclusion

References

Chapter 10: Natural Polymers–-A Boon for Drug Delivery

10.1 Introduction

10.2 Acacia

10.3 Agar

10.4 Alginate

10.5 Carrageenan

10.6 Cellulose

10.7 Chitosan

10.8 Dextran

10.9 Dextrin

10.10 Gellan Gum

10.11 Guar Gum

10.12 Inulin

10.13 Karaya Gum

10.14 Konjac Glucomannan

10.15 Locust Bean Gum

10.16 Locust Bean Gum

10.17 Pectin

10.18 Psyllium Husk

10.19 Scleroglucan

10.20 Starch

10.21 Xanthan Gum

References

Index

Renewable Polymers

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Preface

It has been a long-term desire to replace polymers from fossil fuels with the more environmentally friendly polymers generated from renewable resources. Although a lot of effort has been devoted to the development of such polymers, in most cases however, the polymers from renewable resources were costly and did not match the properties of the fossil fuel-based polymers. Consequently, in the last decades, their importance and use declined due primarily to the rise of the fossil-based raw resources from which a large number of low cost polymers could be synthesized. These polymers had also, in general, superior properties than the polymers obtained from renewable resources. However, with the recent advancements in synthesis technologies and the discovery of new functional monomers, research in natural polymers has surged and has shown strong potential in generating better property polymers from renewable resources. Thus, this book aims to present these research successes by underlining the wide potential of the renewable polymers for large number of applications.

Chapter 1 introduces the reader to various polymers derived from renewable resources. Different polymer systems like naturally renewable methylene butyrolactones, renewable rosin acid-degradable caprolactone block copolymers, plant oils derived polymers, biosourced stereocontrolled polytriazoles, monoterpene based polymers, biosourced 2-(Methacryloyloxy)ethyl tiglate based polymers, rapeseed cake residue based polymers, limonene derived polymers, polylactides, castor oil based thermosets are described. Chapter 2 specifically demonstrates the design, synthesis, properties and applications of plant oil based polymers. The authors present reactions of triglyceride, a major component in natural oils, which can be directly polymerized under cationic conditions or functionalized to various moieties followed by either free-radical or cross-linking polymerization reactions to generate a wide spectrum of polymers having soft, rubbery, elastic, or toughening properties. Chapter 3 presents an elaborate review of acid mediated polymerization techniques for the generation of green polymers. Progress in both homogenous and heterogeneous initiator systems are described. Chapter 4 presents the production of polyhydroxyalkanoates (PHA) from olive oil based wastewater. The advantage of olive oil mill effluents OMEs to be easily fermentable into volatile fatty acids and other suitable substrates for PHA production are demonstrated. Chapter 5 describes the use of atom transfer radical polymerization techniques for the production of polymers from renewable resources. The general considerations of ATRP along with a few case studies are reviewed. Chapter 6 describes the renewable polymers derived from transgenic crop plants. The authors review the great progress made in the production of bio-polymers in plants by gene technology owing to the careful selection of production compartments like chloroplast or endoplasmic reticulum (ER), production organs like seeds or tubers as well as the selection and combination of genes involved in the synthesis. Chapter 7 provides an overview of a range of biomass-based polymers (like polycarbonates, polyesters and polyamides) prepared through polycondensation chemistry. An overview of the biopolymers (e. g. polyesters, polyamides and poly(ester amide)s) based on succinic acid and its derivatives is provided in Chapter 8. Recent progress in the synthesis, characterization, and physical properties studies of the poly-Schiff-base, polyester, polyamide, polyurethane, polybenzoimidazole, and polyoxadiazole type furanic polymers from 5-Hydroxymethylfurfural (HMF) derived monomers are discussed in Chapter 9. Chapter 10 reviews the recent efforts and approaches exploiting the natural materials in developing drug delivery systems.

It gives me immense pleasure to thank Scrivener Publishing and John Wiley & Sons for kind acceptance to publish the book. I dedicate this book to my mother for being constant source of inspiration. I express heartfelt thanks to my wife Preeti for her continuous help in co-editing the book as well as for her ideas to improve the manuscript.

Vikas Mittal

July 12, 2011

List of Contributors

Ananda S. Amarasekara is an Associate Professor of Chemistry at Prairie View A&M University, Texas, USA, and he received his PhD in organic chemistry from City University of NewYork. His research interests are in biomass based chemicals, polymeric materials, and fuels. Dr. Amarasekara has authored or co-authored over 70 peer reviewed research publications.

Lorenzo Bertin is Assistant Professor at the Department of Civil, Environmental, and Materials Engineering of Alma Mater Studiorum University of Bologna (Italy). His research activity is mainly focused on the valorization of organic wastes by means of anaerobic biotechnological processes, carried out under both methanogenic or acidogenic, and by the extraction or biotechnological production of added value natural molecules.

Mario Beccari is a Senior Professor at the Faculty of Mathematical, Physical and Natural Sciences of Sapienza University of Rome (Italy). He is a Member of the Scientific Council of the Department of Earth and Environment of CNR and a Member of the Scientific Council of the Institute of Italian Encyclopaedia. He is the co-Editor of the Encyclopaedia of Hydrocarbons (published by ENI and the Institute of Italian Encyclopaedia). His scientific activity is focused on the following areas: hydrocarbon oxidation processes, evaporation desalination processes, advanced processes of treatment/disposal of wastewaters and wastes. He is author of about 150 scientific papers, many of them published in international journals.

Inge Broer is a molecular biologist and holds the Professorship for Agrobiotechnology and Risk Assessment for Bio- and Gene Technology at the University of Rostock in Germany. Her research is focussed on the usage of transgenic plants for a sustainable agriculture involving the production of vaccines and biodegradable polymers in transgenic plants, as well as the environmental influence on transgene expression and risk assessment on the plants produced in the group.

Inna Bretz studied chemistry and chemical education at the University of Karaganda, Kazakhstan, and at the Technische Universität Berlin, where she prepared her PhD thesis on poly (lactic acid). She joined Fraunhofer UMSICHT in 2006 as a senior scientist working on polymer chemistry using bio-based raw materials.

Tina Hausmann is currently pursuing her PhD in the Agrobiotechnology and Risk Assessment for Bio- and Gene Technology department at the University of Rostock in Germany. Her research interests are the optimization of cyanophycin in commercial tobacco lines and the usage of cyanophycin as feed additive and its storage in silage.

Duy H. Hua is a University Distinguished Professor at the Department of Chemistry, Kansas State University. His research interests include design, synthesis, and application of renewable polymers, nanomaterials, design, synthesis, and bio-evaluation of anti-Alzheimer, anti-norovirus, and anti-cancer compounds. Hua has received numerous awards including the Alumni Achievement Award from Southern Illinois University at Carbondale, Commerce Bank Distinguished Graduate Faculty Award, and Higuchi-University of Kansas Endowment Research Achievement Awards.

Stephan Kabasci is a chemical engineer and prepared his PhD at the Technische Universität Dortmund. He has been business unit manager of “Renewable Resources” at Fraunhofer UMSICHT since 2004. His main research areas are biogas technology and the production of polymers and plastic materials from renewable resources.

Stewart P. Lewis is a polymer scientist, an inventor, a part-time professor, and an entrepreneur running his own research for hire business (Innovative Science Corporation). He invented systems for the aqueous polymerization of isobutene using chelating diboranes and discovered that sterically hindered pyridines react with carbocations that are paired with weakly coordinating anions. Recently he has invented a number of novel polymerization systems for the preparation of high molecular weight grades of isobutene polymers in a more sustainable manner as well as additional methodologies for aqueous carbocationic polymerization.

Mauro Majone is Associate Professor of Chemical Engineering at the Department of Chemistry, Sapienza University of Rome (Italy). Main research interests are in the field of biological and chemical/physical processes for treatment of wastes and wastewaters, remediation of polluted soils and groundwater, environmental and industrial biotechnologies. He is author of more than 100 papers on international scientific journals and books with peer review and more than 100 communications to scientific conferences and other publications.

Robert T. Mathers obtained his PhD from The University of Akron in Polymer Science. After two years of postdoctoral research at Cornell University in the Department of Chemistry and Chemical Biology, he joined Pennsylvania State University where he is an Associate Professor of Chemistry. His research interests focus on polymerization methods that integrate renewable resources, such as monoterpenes and plant oils, with catalysis. Robert recently served as coeditor for the Handbook of Transition Metal Polymerization Catalysts (Wiley) and Green Polymerization Methods: Renewable Starting Materials, Catalysis, and Waste Reduction (Wiley-VCH).

Bart A. J. Noordover received his PhD degree in Polymer Chemistry from the Eindhoven University of Technology, the Netherlands. His research interests include step-growth polymerization, molecular, thermal and mechanical characterization as well as structure-property relations of engineering plastics, elastomers and coatings. He currently holds a position of Researcher at the Laboratory of Polymer Chemistry at the Eindhoven University of Technology.

Keshar Prasain is now perusing his PhD in organic chemistry at Kansas State University under Duy H. Hua. His research focuses on synthesis and characterization of triglyceride based polymers and synthesis of laccase inhibiting compounds. He has received graduate classroom and department research awards from the Department of Chemistry, Kansas State University.

N. Rajesh is an Assistant Professor in the Department of Biochemistry at CSI Holdsworth Memorial Hospital and College, Mysore, India. He obtained his PhD in Polymer Science from the University of Mysore. He has 15 research papers to his credit in international journals along with 20 publications in proceedings of national & international conferences. His research interest centers on the fields of biopolymers for sustained drug delivery and transdermal drug delivery systems.

Valluru Ravi is a Lecturer in the Department of Pharmaceutics at JSS College of Pharmacy, Mysore, India. He is pursuing his PhD in Pharmacy from the University of Mysore. He has 12 research papers to his credit in international journals along with 15 publications in proceedings of national & international conferences. His research interest is on biopolymers for use in drug delivery systems.

Kattimuttathu I. Suresh is a Senior Scientist at the Organic Coatings & Polymers Division of the Indian Institute of Chemical Technology (CSIR), India and is involved in basic and applied research in the broad areas of Polymer Science and Technology. Specific research interests are in the area of polymer synthesis, structure–-property relationship studies and polymers from renewable resources. He is recipient of CSIR-DAAD (Germany) fellowship and the Marie Curie fellowship of the European Commission.

N. Uma is an Assistant Professor in the Department of Biochemistry at BGS International Foundation for Health Science, Mysore, India. She is pursuing her PhD in Chemistry from the University of Mysore. She has 4 research papers to her credit in international journals along with 7 publications in proceedings of national & international conferences. Her research interest centers on the fields of metal complexes materials and medicinal chemistry.

Francesco Valentino is a PhD student in chemical engineering at the Department of Chemistry, Sapienza University of Rome (Italy). Main research interests are in the field of biochemical processes for production of added value materials from wastewater and simultaneous treatment of wastewaters.

Marianna Villano is a postdoctoral researcher at the Department of Chemistry of Sapienza University of Rome (Italy). She earned a PhD in Industrial Chemical Processes from the same University in 2011. Her main research interests are in the field of biological processes for polyhydroxyalkanoates production and bioenergy generation using mixed microbial cultures.

Chapter 1

Polymers from Renewable Resources

V. Mittal

Chemical Engineering Department, The Petroleum Institute, Abu Dhabi, UAE

Abstract

In the modern world, the importance and use of macromolecular materials based on renewable resources declined owing to the rise of the fossil based raw resources from which a large number of low cost polymers could be synthesized. These polymers had also, in general, superior properties than the polymers obtained from renewable resources. The high price of renewable resourced-based polymers also caused limitations in their use. However, changing world scenarios have once again thrusted the macromolecular materials from renewable resources to the forefront of research and application. Reasons for such a paradigm shift are: dwindling amounts of fossil fuels, increasing awareness regarding the environment and increasing price of fossil fuels. Recent advances in the synthesis and properties of polymers from renewable resources with good properties and potentially low costs have kindled the hopes that the replacement of the conventional fossil-based polymers with these renewable polmers will be permanent and commercially economic.

Keywords: Naturally renewable methylene butyrolactones, rosin acid, plant oils, polytriazoles, monoterpene, rapeseed, limonene, lactides, nanocomposites, thermosets

1.1 Introduction

Macromolecular materials based on renewable resources have found applications in various human activities for centuries. In the modern world, their importance and use declined owing to the rise of the fossil based raw resources from which a large number of low cost polymers could be synthesized. These polymers had also, in general, superior properties than the polymers obtained from renewable resources. The high price of renewable resources based polymers also caused the declination in their use. However, changing world scenarios have once again thrusted the macromolecular materials from renewable resources to the forefront of research and application. Reasons for such a paradigm shift are: dwindling amounts of fossil fuels, increasing awareness regarding the environment and increasing price of fossil fuels. Apart from that, recent advances in the synthesis and properties of polymers from renewable resources with good properties and potentially low costs have kindled the hopes of the replacement of the conventional fossil based polymers with these materials. A lot of research effort has been ongoing in order to further explore the novel renewable recourses as well as to modify the currently existing polymers derived from renewable polymers. In a recent comprehensive review on the subject [1], Gandini also underlined the importance associated with these materials but also pointed towards more efforts to be done in order to realize the true commercialization of such materials. There are many polymers which are more abundant in nature than and have also received maximum research attention like cellulose, chitin, starch etc. These materials find uses either in the unmodified state or after suitable bulk or surface modifications. The hydroxyl groups in polysaccharides are commonly used to modify these materials and to add required chemical functionality. As the OH groups are involved in the modification reactions, the corresponding grafting processes include the typical condensation reactions like esterification, etherification, and formation of urethanes etc. Figure 1.1 shows the basic structures of one of the most abundant polysaccharides in nature like cellulose, chitin etc. The forms of applications of these polymers have also diversified; the polymers are used not only as matrices, but also as fibers or fillers for reinforcement of other polymers. Apart from the above mentioned most abundant polymers, many other interesting polymers with good properties have also been developed in the recent years, which make the application spectrum of these materials very wide. Examples of a few of polymer materials derived from renewable resources are discussed in the next sections.

FIGURE 1.1 Structures of the most abundant polysaccharides in nature: (I) cellulose, (II) chitin, (III) chitosan, (IV) amylose and (V) amylopectin.

Reproduced from reference 1 with permission from American Chemical Society.

1.2 Naturally Renewable Methylene Butyrolactones

Hu et al. [2] reported the polymerization of naturally renewable methylene butyrolactones by half-sandwich indenyl rare earth metal dialkyls. Monomers eg. α-methylene-γ-butyrolactone (MBL) and γ-methyl-α-methylene-γ-butyrolactone (MMBL) were used. Four half-sandwich dialkyl rare earth metal (REM) complexes incorporating a disilylated indenyl ligand were used for the coordination-addition polymerization of these methylene butyrolactones. Figure 1.2 shows the schematic of methylene butyrolactone monomers (M)MBL and their polymers P(M)MBL along with comparison with MMA and PMMA. Structures of half-sandwich REM dialkyl catalysts are also shown. The authors observed several differences in catalytic behavior of half-sandwich REM catalysts and well-studied sandwich REM catalysts after initial screening for the polymerization of methyl methacrylate. All four catalysts exhibited exceptional activity for polymerization of MMBL in DMF, achieving quantitative monomer conversion in <1 min with a 0.20 mol% catalyst loading.

FIGURE 1.2 Schematic of methylene butyrolactone monomers (M)MBL and their polymers P(M)MBL along with comparison with MMA and PMMA. Structures of half-sandwich REM dialkyl catalysts are also shown.

Reproduced from reference 2 with permission from American Chemical Society.

Miyake et al. [3] similarly reported the living polymerization of naturally renewable butyrolactone-based vinylidene monomers α-methylene-γ-butyrolactone (MBL) and γ-methyl-α-methylene-γ-butyrolactone (MMBL) by ambiphilic silicon propagators. Part from homopolymers, block copolymers of MBL and MMBL with MMA as well as block and statistical copolymers of MBL with MMBL with well defined characteristics could also be readily synthesized. The glass transition temperatures of the atactic homopolymers, PMBL and PMMBL, were observed to be 194 and 225°. These values were significantly higher than the glass transition temperature of atactic PMMA (approx. 90° for PMBL and approx 120° for PMMBL). The polymerization of MBL in CH2Cl2 at ambient temperature was observed to be heterogeneous with low polymer yield and bimodal MWD. However, in the case of MMBL, a homogeneous reaction was obtained which achieved completion in 10 min even with a low catalyst loading of 0.05 mol%. Thus, polymers with controlled low to high molecular weight and narrow molecular weight distributions (1.01–1.06) were obtained. All copolymers produced also exhibited exhibit unimodal and narrow MWD’s of nearly 1.03. The block copolymer PMMBL-b-PMBL displayed two glass transition peaks in the DSC signal corresponding to the PMBL and PMMBL blocks as shown in Figure 1.3a, while the statistical copolymer PMMBLco-PMBL showed only one glass transition temperature signal. As shown in Figure 1.3b, the effect of Mn on the Tg of PMMBL was also investigated. From the leveling off point of the generated curve, a critical molecular weight for PMMBL was estimated which was over 40 kg/mol.

FIGURE 1.3 (A) DSC curves for (a) PMBL, (b) PMMBL, (c) PMMBL-b-PMBL, and (d) PMMBL-co-PMBL and (B) Plot of Tg vs Mn of atactic PMMBL.

Reproduced from reference 3 with permission from American Chemical Society.

1.3 Renewable Rosin Acid-Degradable Caprolactone Block Copolymers

Wilbon et al. [4] reported the synthesis of block copolymers based on renewable rosin acid-degradable caprolactone by atom transfer radical polymerization and ring opening polymerization. For the two-step sequential polymerization, either poly(2-acryloyloxyethyl dehydroabietic carboxylate)-OH (PAEDA-OH) or poly(ε-caprolactone)-Br (PCL-Br) were used as macroinitiators. Two-step sequential polymerization resulted in the generation of well-defined block copolymers with low polydispersity. One-pot polymerization was also carried out with three different sequential feeds of AEDA and ε-CL monomers. The control of one-pot polymerization was observed to depend on the interactions of coexisting ATRP catalysts and ROP catalysts.

Figure 1.4 shows the DSC thermograms of the PCL-Br homo-polymer and the block copolymers. PCL-Br showed a characteristic strong endothermic melting peak at approximately 55°. The thermal behaviors of diblock copolymers depended on the length and fraction of the PCL block in the block copolymers. In the block

FIGURE 1.4 DSC thermograms of polymers PCL-Br, PAEDA-b-PCL-OH, and PCL-b-PAEDA-Br.

Reproduced from reference 4 with permission from American Chemical Society.

FIGURE 1.5 Tapping-mode AFM height images of (a) PCL41-b-PAEDA41-Br and (b) PAEDA50-b-PCL500-OH.

Reproduced from reference 4 with permission from American Chemical Society.

copolymer with high fractions of PAEDA (PCL41-b-PAEDA41-Br), only the Tg of the PAEDA block at approximately 50° was observed and suppression of the PCL crystallization resulted. For block copolymer with high fraction of the PCL block (PAEDA50-b-PCL500-OH), a strong endothermic peak at approximately 55° corresponded to the melting of the PCL block. The AFM analysis reported in Figure 1.5 also confirmed the findings of differential scanning calorimetry. AFM images of thin films of block copolymers with a short length of the PCL block (PCL41-b-PAEDA41-Br) were observed to be very smooth, whereas the AFM height images of block copolymers with high fractions of the PCL block (PAEDA50-b-PCL500-OH) revealed the formation of small crystals.

1.4 Plant Oils as Platform Chemicals for Polymer Synthesis

Ligadas et al. [5] reviewed the importance of plant oils as platform chemicals for the synthesis of polyurethanes. In one such example, synthesis of vegetable oil-based polyols for polyurethane synthesis through reactions involving the ester groups was demonstrated. As shown in Figure 1.6, functionalization of oleic sunflower oil with secondary hydroxyl groups was achieved via photoperoxidation and subsequent reduction. Oleic sunflower oil was oxidized photochemically with singlet oxygen generated

FIGURE 1.6 Schematic of the functionalization of oleic sunflower oil with secondary hydroxyl groups.

Reproduced from reference 5 with permission from American Chemical Society.

with a high pressure sodium-vapor lamp and tetraphenylporphyrin (TPP) as sensitizer in an oxygen-saturated medium. By following this process, a mixture of isomeric allylic hydroperoxides was obtained as shown in Figure 1.6a. These were further reduced to unsaturated hydroxylated oil using sodium borohydride as shown in Figure 1.6b. The authors transformed the resulting allylic alcohol triglyceride derivative to the saturated analogues as shown in Figure 1.6c by hydrogenation at room temperature using 5% charcoal supported platinum as catalyst. The polyols were then used for the synthesis of polyurethane polymers. Similarly, synthesis of vegetable oil-based polyols through polymerization of C-C double bonds & subsequent hydrolysis of ester groups and synthesis of fatty acid-based polyols etc. were reported.

1.5 Biosourced Stereocontrolled Polytriazoles

Besset et al. [6] reported the synthesis of biosourced stereocontrolled polytriazoles from click chemistry step growth polymerization of diazide and dialkyne dianhydrohexitols. Figure 1.7 demonstrates the schematic of synthesis of these polymers. The obtained polymers had a good thermal degradation resistance as temperatures to 10% degradation were observed to be in the range of 325–347°.

FIGURE 1.7 Schematic of synthesis of polytriazoles by step growth polymerization of diazides and dialkynes.

Reproduced from reference 6 with permission from American Chemical Society.

The amounts of residual ashes were 25–30 wt% in the thermogravimetric analysis. The polymers displayed high glass transition temperatures in the range of 125–166°. The molecular weights of the generated polymers were also high and lied in the range of 8–17 kg/mol. The polymers had good solubility in DMSO and DMF at room temperature. The authors reported that the monomer stereochemistry proved to be a crucial parameter aiming at generating polymers with high glass transition temperatures. Several polytriazoles were observed to exhibit high values of PDI (3.8–5.7) indicating broadening of molecular weight distribution. This may have originated from the additional presence of high molar mass species due to the formation of aggregates in hot DMSO and of low molar masses cyclic species.

1.6 Polymers from Naturally Occurring Monoterpene

Kobayashi et al. [7] reported the controlled polymerization of a cyclic diene prepared from the ring-closing metathesis of a naturally occurring monoterpene as shown in Figure 1.8. The monoterpene myrcene (1) was obtained from plants or from the pyrolysis of pinene and the cyclic diene 3-methylenecyclopentene (2) could be prepared from 1 by ring-closing metathesis reaction. Polymerization of cyclic diene was studied using radical, anionic, and cationic polymerization. Radical polymerization of cyclic diene using radical initiator AIBN exhibited low conversion in benzene solution, but bulk polymerization led to a polymeric product in 58% yield after 20 h at 80°. Anionic polymerization was carried out using sec-butyllithium (s-BuLi) as initiator and polymerization reactions were observed to be rapid at low temperature. In the case of

FIGURE 1.8 Synthesis scheme for the generation of polymer based on naturally occurring monoterpene.

Reproduced from reference 7 with permission from American Chemical Society.

cationic polymerization, the polymer obtained using i-BuOCH(Cl) Me/SnCl4/Et2O had a broad molecular weight distribution, on the other hand, the i-BuOCH(Cl)Me/ZnCl2/Et2O system generated regiopure polymer with controlled molecular weight and narrow molecular weight distribution. The number average molecular weight was observed to increase wit conversion and was in good agreement with the calculated values. Apart from that, a control on the molecular weight could be achieved by changing the feed molar ratios of monomer to initiator.

1.7 Polymerization of Biosourced 2-(Methacryloyloxy) ethyl Tiglate

Kassi et al. [8] reported the group transfer polymerization (GTP) of tiglic acid ester after introducing it in a methacrylate monomer, 2-(methacryloyloxy) ethyl tiglate (MAET). The monomer underwent smooth polymerization to yield linear polymers of narrow molecular weight distributions. The MAET monomer was also block copolymerized with a hydrophilic methacrylate, a hydrophobic methacrylate, and a dimethacrylate to obtain, respectively, amphiphilic, double-hydrophobic, and star polymers of that tiglate ester. The authors first attempted direct polymerization of the simplest ester of tiglic acid, methyl tiglate (MT) using various controlled polymerization methods: group transfer polymerization (GTP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization, but the methyl tiglate monomer could not be polymerized, thus, requiring its insertion in a methacrylate monomer.

Figure 1.9a demonstrates the schematic of the synthetic strategy followed for the preparation of MAET and its homo- and copolymerization with conventional methacrylates. Homopolymers of MAET covered a range of molecular weight values and relatively narrow distributions, corresponding to PDIs lower than 1.5 in all cases. Various copolymers were synthesized using GTP to copolymerize MAET with methyl methacrylate (MMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), or ethylene glycol dimethacrylate (EGDMA), the GPC traces of which are shown in Figure 1.9b.

FIGURE 1.9 (a) Schematic of synthesis and group transfer polymerization of the tiglic acid-bearing methacrylate monomer 2-(methacryloyloxy)ethyl tiglate (MAET) and (b) GPC traces of the star homopolymer of MAET and the MAET-MMA block copolymer, as well as those of their linear poly-MAET precursors.

Reproduced from reference 8 with permission from American Chemical Society.

1.8 Oxypropylation of Rapeseed Cake Residue

Serrano et al. [9] studied the oxypropylation of rapeseed cake residue generated in the biodiesel production process. The authors carried out the reaction by suspending the rapeseed cake residue in propylene oxide in the presence of a basic catalyst and heating the resulting mixture at 160° in a nitrogen atmosphere which led to the synthesis of the polyol with good characteristics. Almost total conversion of the solid substrate into polol was achieved. Figure 1.10 shows the

FIGURE 1.10 TGA thermograms of rapeseed pellets and oxypropylated product.

Reproduced from reference 9 with permission from American Chemical Society.

TGA thermograms of the rapeseed pellets and oxypropylated product. Significant differences in the thermal behavior before after the oxypropylation reaction were observed. The hydrophilic character of the sample decreased after oxypropylation as the extent of the first mass loss, from room temperature to about 150°, associated with the evaporation of water present in the samples, decreased. The introduction of propylene oxide (PO) also led to a decrease in the degradation temperature of the oxypropylated product. The differential scanning calorimetry (DSC) analysis revealed that the oxypropylated product was a branched polymer bearing numerous OH groups per macromolecule with a glass transition temperature of 33°.

1.9 Copolymerization of Naturally Occurring Limonene

Satoh et al. [10] reported the living radical chain copolymerization of naturally occurring limonene with maleimide. Figure 1.11 shows the schematic of the reaction between d-limonene (M1) and phenylmaleimide (M2). M1M2• radical favored M2 while M2M2• radical exclusively reacted with M1 thus leading to 1:2 radical copolymerization.

FIGURE 1.11 Schematics of AAB-sequence radical copolymerization of d-limonene (M1) and phenylmaleimide (M2).

Reproduced from reference 10 with permission from American Chemical society.

The copolymerization reactions were examined in DMF, cumyl alcohol and fluorinated cumyl alcohol using 2,2’-azobisisobutyronitrile (AIBN) as a radical initiator at 60°. The glass transition temperatures obtained for the copolymers were significantly higher (220–250°) owing to the higher incorporation of maleimides as well as the rigid alicyclic structure of the terpenes. Apart from that, controlled/living radical polymerization was carried out with a reversible addition-fragmentation chain transfer (RAFT) agent which led to the synthesis of end-to-end sequence-regulated copolymers with controlled molecular weights.

1.10 Polymerization of Lactides

Darensbourg et al. [11] reported the ring-opening polymerization (ROP) of lactides catalyzed by natural amino-acid based zinc catalysts. All zinc complexes used in the study were observed to be very effective catalysts for the ring-opening polymerization of lactides at ambient temperature, producing polymers with controlled and narrow molecular weight distributions. The polymerization reaction using different catalysts was found to be first-order as shown in Figure 1.12.

FIGURE 1.12 ln([LA]0/[LA]t) vs time plots for the ring opening polymerization of D-lactide (blue solid circles) and L-lactide (red solid triangles) catalyzed by various zinc complexes at ambient temperature.

Reproduced from reference 11 with permission from American Chemical Society.

The molecular weights and polydispersity indices of the polymers after purification were determined by gel permeation chromatography (dual RI and light scattering detectors) in THF solvent using polystyrene macromolecules as a standard. The polymerization processes was observed to be similar to a living system owing to a linear relationship between molecular weight, Mn and % conversion and low polydispersity index in the range of 1.05–1.07. The differential scanning calorimetry (DSC) analysis led to the observation that the thermal properties of the generated polylactide polymers were dependant on their tacticity. Isotactically pure polylactide generated from the ring opening polymerization of L-lactide was observed to be highly crystalline with a glass transition temperature of 60°. The polymer showed peak crystallization and melting temperatures of 90 and 178° respectively. On the other hand, the heterotactically enriched polymers generated from the ring opening polymerization of rac-lactide exhibited glass transition temperatures which increased with increasing Pr values. The authors also reported that the reactivities of the various catalysts were greatly affected by substituents on the Schiff base ligands, with sterically bulky substituents being rate enhancing.

Jiang et al. [12] reported the synthesis of PEO-grafted polylactides. Novel glycolides with pendent oligo(ethylene oxide) monomethyl ether substituents were subjected to ring-opening polymerization using 4-tert-butylbenzyl alcohol as the initiator and Sn(2-ethylhexanote)2 as the catalyst. It resulted in the synthesis of homogeneous oligo(ethylene oxide)-grafted polylactides with high molecular weights and low polydispersities. Figure 1.13 details the synthesis process. Polymers with different oligo(ethylene oxide) chains exhibited different behaviors, e.g. polymers with short oligo(ethylene oxide) chains (1 or 2 ethylene oxide repeat units) were more hydrophilic than polylactide but insoluble in water. On the other hand, polymers having 3 or 4 ethylene oxide repeat units were observed to be water-soluble.

The thermoresponsive behavior of the polymer solutions was also monitored by variable temperature dynamic light scattering measurements (DLS). When the solution of polymer poly(3,6-bis(7,10,13,16-tetraoxaheptadecyl)-1,4-dioxane-2,5-dione) was heated from 10 to 21°, the average hydrodynamic radius of the polymer particles did not show any change. Further heating led to a sudden increase in the average hydrodynamic radius owing to polymer agglomeration. Similarly, for polymer

FIGURE 1.13 Synthesis of PEO-grafted polyglycolides.

Reproduced from reference 12 with permission from American Chemical society.

poly(3,6-bis(7,10,13,16,19-pentaoxaeicosyl)-1,4-dioxane-2,5-dione) poly(5d) (3 mg/mL), between 25 and 38°, the average hydrodynamic radius of the particles was constant, but heating the solution to 39° induced an increase in hydrodynamic radius.

Pitet et al. [13] combined ring-opening metathesis polymerization and cyclic ester ring-opening polymerization to form ABA triblock copolymers from 1,5-cyclooctadiene (COD) and D,L-lactide. The authors prepared hydroxyl-functionalized telechelic polyCOD by chain transfer during ring-opening metathesis polymerization of COD using the acyclic chain transfer agent cis-1,4-diacetoxy-2-butene. The hydroxyl-functionalized telechelic polyCOD was used as macroinitiator for the polymerization of lactide to form a series of triblock copolymers poly(D,L-lactide)-poly(cyclooctadiene)-poly(D,L-lactide) (LCL) as shown in Figure 1.14a. DSC analysis was carried out by first heating the samples to 160°, annealing for 5 min at 160°, cooling to -100° at 10° min−1 and reheating to 120° at 10° min−1. Glass transition temperatures around 47° for the PLA blocks and -95° for the PCOD blocks were observed. The authors observed a decrease in both crystallinity and peak

FIGURE 1.14 (a) Synthesis of triblock copolymer LCL and (b) tensile measurements for selected LCL triblock copolymers. The fracture point is represented by the symbol x.

Reproduced from reference 13 with permission from American Chemical Society.

melting point with increasing PLA content in the copolymers. Microphase separation was evidenced by well-defined peaks in the one-dimensional SAXS profiles. The mechanical performance of the copolymers is demonstrated in Figure 1.14b. The numbers in the parenthesis indicate the molecular weight of the blocks. The modulus, tensile strength, and yield strength of the copolymers was observed to increase with increasing molecular weight of the LCL samples. The yield strain and strain at break did not exhibit noticeable dependence on composition or molecular weight. The authors observed that the samples with the highest PLA content exhibited the largest modulus, tensile strength, and yield strength values with ultimate elongations which were an order of magnitude greater than typical values for PLA homopolymer.

1.11 Nanocomposites Using Renewable Polymers

Pranger et al. [14] used an in situ polymerization approach to produce polyfurfuryl alcohol (PFA) nanocomposites without the use of solvents or surfactants using either cellulose whiskers or montmorillonite clay as fillers. Figure 1.15 shows the schematic of cellulose whiskers based nanocomposites with polyfurfuryl alcohol. Figure 1.15a showed the needle-like morphology of cellulose whiskers which were produced from acid hydrolysis of microcrystalline cellulose (MCC). It was further observed that the average diameter of the whiskers was 10 nm, and the aspect ratio is in the range of 50–100. Both cellulose whiskers and montmorillonite clay first catalyzed the in-situ polymerization reaction, thereby eliminating the use of strong mineral acid catalysts, and subsequently enhancing the thermal stability of the generated nanocomposites. In the nanocomposites based on cellulose whiskers, onset of degradation (temperature at 5% weight loss) was observed to be 323°, which was 20–30° higher compared to the nanocomposites reinforced with montmorillonite.

1.12 Castor Oil Based Thermosets

Xia et al. [15] reported thermoset polymers based on castor oil which had varied crosslink densities and were prepared by ring-opening metathesis polymerization (ROMP). Two monomers based

FIGURE 1.15 AFM image of cellulose whiskers from acid hydrolysis of microcrystalline cellulose, (b) line scan, the position of which is indicated by the bar in the AFM image and (c) schematic of the in-situ polymerization of cellulose whiskers–-poly(FA) nanocomposites.

Reproduced from reference 14 with permission from American Chemical Society.

on castor oil namely norbornenyl-functionalized castor oil (NCO), which had approx. 0.8 norbornene rings per fatty acid chain and norbornenyl-functionalized castor oil alcohol (NCA) with approx. 1.8 norbornene rings per fatty acid chain were prepared by the authors. Different ratios of NCO/NCA were subjected to ring-opening metathesis polymerization (ROMP) using the Grubbs catalyst, which resulted in the generation of rubbery to rigid plastics. The crosslink densities varied from 318 to 6028 mol/m3. Figure 1.16 shows the storage modulus and tan δ curves for the polymers as a function of temperature for different NCO/NCA ratios. Presence of only one peak in the tan δ versus T curves for all of the copolymers indicated the generation of homogeneous

FIGURE 1.16 Dynamic mechanical properties of polymers.

Reproduced from reference 15 with permission from Elsevier.

copolymers. The thermal properties, e.g. the glass transition temperature and room temperature storage moduli improved with an increase in the NCA content.

References

1. A. Gandini, Macromolecules, Vol. 41, p. 9491, 2008.

2. Y. Hu, X. Xu, Y. Zhang, Y. Chen, and E.Y.-X. Chen, Macromolecules, Vol. 43, p. 9328, 2010.

3. G.M. Miyake, Y. Zhang, and E.Y.-X. Chen, Macromolecules, Vol. 43, p. 4902, 2010.

4. P.A. Wilbon, Y. Zheng, K. Yao, and C. Tang, Macromolecules, Vol. 43, p. 8747, 2010.

5. G. Lligadas, J.C. Ronda, M. Galia, and V. Cadiz, Biomacromolecules, Vol. 11, p. 2825, 2010.

6. C. Besset, J.-P. Pascault, E. Fleury, E. Drockenmuller, and J. Bernard, Biomacromolecules, Vol. 11, p. 2797, 2010.

7. S. Kobayashi, C. Lu, T.R. Hoye, and M.A. Hillmyer, Journal of the American Chemical Society, Vol. 131, p. 7960, 2009.

8. E. Kassi, and C.S. Patrickios, Macromolecules, Vol. 43, p. 1411, 2010.

9. L. Serrano, M.G. Alriols, R. Briones, I. Mondragon, and J. Labidi, Ind. Eng. Chem. Res., Vol. 49, p. 1526, 2010.

10. K. Satoh, M. Matsuda, K. Nagai, and M. Kamigaito, Journal of the American Chemical Society, Vol. 132, p. 10003, 2010.

11. D.J. Darensbourg, and O. Karroonnirun, Inorganic Chemistry, Vol. 49, p. 2360, 2010.

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14. L. Pranger, and R. Tannenbaum, Macromolecules, Vol. 41, p. 8682, 2008.

15. Y. Xia, and R.C. Larock, Polymer, Vol. 51, p. 2508, 2010.

Chapter 2

Design, Synthesis, Property, and Application of Plant Oil Polymers

Keshar Prasain and Duy H. Hua

Department of Chemistry, 213 CBC Building, Kansas State University, Manhattan, KS, U.S.A.

Abstract

Most petroleum polymers are not biodegradable and efforts have been made to produce biodegradable and possibly biocompatible plant oil polymers. Triglyceride, a major component in natural oils, can be directly polymerized under cationic conditions or functionalized to various moieties followed by either free-radical or cross-linking polymerization reactions to generate a wide spectrum of polymers having soft, rubbery, elastic, or toughening properties. The materials are used in adhesives, plasticizers, gum-based materials, toughening of rubbers, drug carriers, flame retardants, and others. An understanding of the degree of cross linking, entanglement, and polymer network, would greatly enhance the design of polymers with desired physical properties.

Keywords: Triglyceride, free-radical, cross-linking polymerization, adhesives, flame retardants, polymer network

Abbreviations: AESO: acrylated soybean oil, AFAME: acrylated oleic methyl ester, AHMPA: 3-(acryloxy)-2-hydroxypropyl methacrylate, AIBN: 2,2’-azobis (2-methylpropionitrile), BA: bisphenol A, COGLYMA: maleic half ester of glycerolyis product of castor oil, DMA: dynamic mechanical analysis, DMF: dimethyl formamide, DMSO: dimethyl sulfoxide, DSC: differential scanning calorimetry, HEMA: 2-hydroxyethyl methacrylate, MA: maleic anhydride, MCPBA: m-chloroperoxybenzoic acid, MDI: 4,4’-methylen ebis(phenylisocyanate), MEKP: methyl ethyl ketone peroxide, MMA: - methyl methacrylate, MMPP: maleic anhydride grafted polypropylene, MVI: 1-methyl vinyl isocyanate, NBS: N-bromosuccinimide, NPG: neopentyl glycol, PDI: 1,4-phenylenediisocyanate, PSA: pressure-sensitive adhesives, TDI: 2,4-diisocyanatotoluene, TGA: thermogravimetric analysis, THF: tetrahydrofuran

2.1 Introduction

Polymers and polymeric composites are widely used in various industrial fields. They are lightweight and have demonstrated low assembly costs, excellent mechanical properties, high corrosion resistance, and dimensional stability. Generally, they are made of synthetic chemicals derived from petroleum. As environmentally friendly materials and applications increase, alternative sources of polymers are needed. One alternative source is the utilization of affordable composites from renewable sources, such as natural triglyceride oils, as the main component for the construction of polymers and composites [1]. Triglyceride polymers derived from oils of soybean, sunflower, cotton, and linseed, are considered to be an important class of renewable bio-based materials.

Triglycerides are major components in natural oils derived from plant and animals. They are triesters of glycerol with various fatty acids (Figure 2.1). These fatty acids differ in the carbon chain length ranging from 14 to 22 carbons and have zero to three carbon-carbon double bonds per fatty acid. Some fatty acids have additional functional groups like epoxide in vernonia oil, hydroxyl in castor and lesquerella oils, and ketone in licania oil. The type of fatty acid and the number of C=C bond determine the physical and chemical properties of the triglyceride [2].

Hydrolysis of vegetable oils provides about 15 different fatty acids. Among them the predominant five fatty acids are two saturated, palmitic and stearic, and three unsaturated, oleic, linoleic, and linolenic acid. The structure of a representative triglyceride is depicted in Figure 2.1. The fatty acid compositions of triglycerides

FIGURE 2.1 Structure of a representative triglyceride, 1-oleyl-2-stearyl-3-linoleylglycerol.

vary not only from oil to oil but also within the same oil. Fatty acid compositions in particular oil also vary on the location where the plant is grown. Fatty acids derived from nature have even number of carbon atoms, due to their biosynthesis starting from acetyl coenzyme A, a two-carbon carrier. Fatty acid distributions of some common oils are depicted in Table 2.1 [3].

Plants oils are used mainly for food purpose and as minor components in coatings, plasticizers, lubricants, agrochemicals, and inks as toughening agents or improving the fracture resistance of thermoset polymers. Polymers derived from plant oils would have low toxicity and are biodegradable and biocompatible. Presently, there is a growing interest towards the use of triglycerides as a main constituent of polymers for various applications.

2.2 Triglyceride Polymers

Plant oils have a number of reactive sites such as the double bonds, allylic carbons, ester functions, α-carbons of ester functions, and carbons attached to the oxygen of the ester functions, which may be utilized in various chemical transformations to achieve a number of synthetic intermediates for polymer syntheses. Polymers from triglycerides can be synthesized but not limited to the following strategies:

Conversion of triglycerides to monoglycerides and diglycerides followed by copolymerization.Conversion of triglycerides to fatty acids followed by copolymerization.Functionalization of triglycerides followed by polymerization.

2.2.1 Formation and Copolymerization of Monoglycerides and Diglycerides

Alkyd resins are polyester polymers prepared from the esterification of polyalcohols, polyacids, and fatty acids [4]. They are one of the earliest polymers made from triglycerides and are used in surface coatings. Some of the polymers are described here. The materials include polyesters from monoglycerides obtained from the conversion of plant oil triglycerides via a glycerolysis followed by

Table 2.1 The percent distributions of fatty acids in various plants oils [3].

coupling with various polyacids, cyclic esters, and/or cyclic anhydrides. Alkyd resins have acquired wide usages because of their bioavailability and ease of preparation.

The glycerolysis reaction is a convenient reaction to convert triglycerides 2 to monoglycerides 4 (Scheme 2.1). This involves reacting triglycerides with excess of glycerol (3) and a catalytic amount of white soap at 230° to give predominantly monoglycerides 4 as a mixture of regioisomers [4]. Likely, diglycerides 5 are also present in the soybean oil monoglycerides 4.

Scheme 2.1 A glycerolytic reaction of soybean triglycerides.

Monoglyceride 4 was then used to prepare monoglyceride maleate half esters by the treatment with ~2 equivalents of maleic anhydride and catalytic amounts of triphenylantimony and hydroquinone (as a free-radical scavenger) at 100° to 800° to give monoglyceride bis-maleate half esters 6 (Scheme 2.2) [6]. Copolymerization of compound 6 and styrene with tert-butyl peroxybenzoate as a free-radical initiator at 120–150° gave rigid polymers 7 having load bearing applications. The resin has a glass-transition temperature value of 133° (obtained from dynamic mechanical analysis; DMA) and a storage modulus value of 0.94 GPa at 35°, and a tensile strength of 29.36 MPa and a tensile modulus of 0.84 GPa. The additive effects of rigid diols such as neopentyl glycol (NPG) or bisphenol A (BA) were studied by mixing 4 and NPG or BA separately followed by heating with maleic anhydride (MA) under similar reaction conditions as aforementioned. The resulting mixture was similarly copolymerized with styrene under free-radical

Scheme 2.2 Formation of monoglyceride bis-maleate half esters 6 and copolymerization with styrene.

conditions. The introduction of NPG/MA to 4/MA increased the glass transition temperature (Tg) and the modulus but decreased the tensile strength of the polymer formed. The introduction of BA/MA had no significant change in Tg, but a slight increase in the modulus of the polymer was found [5]. The fatty acid fragments contaminated in the above 4/MA monomers are inactive and do not participate in the polymerization, but behave as a plasticizer reducing the modulus and strength of the polymers. To decrease the plasticizing effect, castor oil, contained 87% of ricinoleic acid (possessing a C12-hydroxyl and C9, C10 double bond functions), was used in place of soybean oil, and the properties of the polymers were similarly studied. The co-polymers prepared from castor oil were found to have improved modulus, tensile strength, and glass transition temperature [6].

A mixture of partial glycerides consisted of diglycerides 9 and monoglycerides 10 was obtained from the treatment of sunflower oil and linseed oil separately with glycerol (~11% by weight) and a catalytic amount of calcium oxide at 230° (Scheme 2.3) [7]. The acid (from fatty acids) and hydroxyl (from diglycerides and monoglycerides) values were determined [8]. The resulting partial glycerides (9 & 10) were esterified with methyl methacrylate (MMA) (molar ratio of hydroxyl groups of 9 & 10 and MMA was 1:2) and a catalytic amount of calcium oxide along with hydroquinone (6% by weight; to inhibit the homopolymerization of MMA) at 200°. Copolymerization of 11 and 12 with styrene (1:1 by weight) and benzoyl peroxide (0.5% by weight) at 100° gave oily resins. Their flexibility, adhesion, water resistance, alkali resistance, acid resistance [9], and other film properties such as viscosities and hardness [7] were measured. The resins exhibited good film properties with good water, alkali, and acid resistance, and appear to be suitable for coating application.

The use of pentaerythriol (16) instead of glycerol in the alcoholysis of triglycerides was found to produce polymers with higher cross-linked densities [6]. The alcoholysis products 17 and 18 of soybean oil and castor oil upon treatment with maleic anhydride produced maleate half esters 19 and 20, respectively, which upon copolymerization with styrene under free-radical conditions afforded polymers with higher cross-linked densities than the polymers obtained from that of COGLYMA, maleate half esters derived from the glycerolysis reaction of castor oil (Scheme 2.4). This is due to the fact that alcoholysis reaction of pentaerythriol (16) with

Scheme 2.3 Formation of partial glycerides/methacryate 11 and 12 and copolymerization with styrene.

Scheme 2.4 Copolymerization of maleate half ester 20 and styrene.

triglycerides produces monoglycerides 18 with higher number of hydroxyl groups providing more reactive sites for malination, thus giving greater number of maleate half ester functions per molecule (compound 20) of triglycerides.

It was found that values of the flexural strength, flexural modulus, storage modulus, and Tg of castor oil based rigid polymers were higher than that of soybean oil based polymers showing castor oil as a better alternative than soybean oil [10]. For castor oil based polymers, the changes in the mechanical properties like storage modulus, glass transition temperature, flexural modulus, and surface hardness by the use of pentaerythriol instead of glycerol in alcoholysis reaction were studied, and results are summarized in Table 2.2.

Results from Table 2.2 show that polymers derived from 19 and 20 have higher storage modulus, glass transition temperature, flexural modulus, flexural strength, and surface hardness than that of COGLYMA using a similar concentration of styrene.

Polymers derived from carbamoylation of partial glycerides 9 and 10 with 1-methylvinyl isocyanate were similarly investigated. Koprululu et al. [11] synthesized triglyceride oil-based 1-methylvinyl urethanes 22 and 23 containing vinylic moieties by starting from

Table 2.2 Mechanical properties of castor-oil-based rigid polymers prepared using 33% weight ratio of styrene.

linseed oil. Glyerolysis of linseed oil with glycerol (8.5% of the oil) at 232° followed by the addition of 0.1% calcium hydroxide under nitrogen atmosphere for 45 minutes gave a mixture of mono- and diglycerides 9 and 10 (see Scheme 2.3). The mixture was treated with an equivalent amount of 1-methylvinyl isocyanate (MVI) in the presence of a catalytic amount (0.14 wt %) of dibutyltin dilaurate as a base to afford urethanes 22 and 23 (Scheme 2.5). The 1-methylvinyl functions of 22 and 23 were copolymerized with styrene in a weight ratio of 1:0.5, and 0.1 wt % of benzoyl peroxide (as a free-radical initiator) in toluene at 65° to give a yellow-colored, transparent, and flexible film. The polymer film obtained has good acid resistance properties, increased thermal resistance, and low hydrophilicity. The properties likely induced from the urethane functions.

2.2.2 Copolymerization of Fatty Acids

Fatty acids are good candidates for the preparation of biodegradable polymers, as they are natural body components and hydrophobic, thus may find applications in coatings, drug carriers, and others. Teomim et al. [12] reported the synthesis of ricinoleic acid-based biopolymers which have properties desirable to be used as drug carriers. Hence, treatment of ricinoleic acid (26) and maleic or succinic anhydride in a molar ratio of 1:2 at 90° for 12 hours in toluene gave ricinoleic acid maleate 28 or ricinoleic acid succinate 27, respectively. A catalytic hydrogenation of the double bond moieties of 28 with palladium and hydrogen (80 atm.) in ethanol furnished 12-hydroxystearic acid succinate 29 (Scheme 2.6).

These diacids were used to couple with sebacic acid (decanedioic acid) to form polyanhydrides as prospective drug carriers. The synthesis involves the formations of mix anhydrides of 28, 29, and 27, separately, with excess of acetic anhydride. The resulting mix anhydrides were treated with sebacic acid, separately, to form sabacic copolymers 28-sabacic, 29-sabasic, and 27-sabacic, respectively by a melt condensation method under vacuum. The melt condensation method was carried out by mixing a 1:1 ratio by weight of the mix anhydride and sabacic acid at 150° under reduced pressure at 0.3 mm Hg for 4 hours with stirring to produce the polyanhydride, a polymer. These sebacic acid copolymers, 28-sabacic, 29-sabacic, and 27-sabacic, were found to have molecular weights of 31,200, 41,000 and 48,700 Daltons, respectively, obtained from GPC analyses. The polymers have low toxicity and are biodegradable due to

Scheme 2.5 Copolymerization of vinyl urethanes 22 and 23 with styrene.

Scheme 2.6 Syntheses of ricinoleic acid succinate 27, maleate 28, and hydroxystearic acid succinate 29, and polymerization with sebacic acid.

their rapid hydrolytic degradation via hydrolysis of the anhydride functions. The polymers are probable candidates of drug carriers.

Pressure-sensitive adhesives (PSA) are used in labels, tapes, films, postage stamps, etc. Currently, the majority of PSA are made from petroleum based acrylate monomers. Since most of the PSA are of disposable nature, it would be desirable to make these materials bio-degradable, providing an opportunity for the use of plant based fatty acids in PSA synthesis. Bunker et al. [13] reported the synthesis of high molecular weight polymers from methyl oleate (30). Oleate 30 can readily be produced from a methanolysis of triglycerides containing oleic acid in their side chain. The polymers were constructed from a polymerization reaction of an acrylate function to be installed to the double bond of methyl oleate (Scheme 2.7). Hence, epoxidation of methyl oleate with formic acid and hydrogen peroxide followed by esterification of the resulting epoxide function with acrylic acid in a ratio of 1:1.5 and a catalytic amount of hydroquinone and AMC-2 at 90° to furnish acrylated oleic methyl ester (32). Self polymerization of 32 via a free-radical reaction using a catalytic amount of 2,2’-azobis(2-aminopropane) dihydrochloride as the initiator provided polymers having a molecular weight of ~106 g/mol, measured by size exclusion chromatography. The glass transition temperature of the polymers was measured by DSC and found to be ~ -40°. These polymers are thought to be of considerable importance in the field of pressure-sensitive adhesives.

Copolymers utilizing a similar methodology as described above with various reactive alkenes were also synthesized. Instead of performing the aforementioned two-step process to synthesize β-hydroxy acrylate 32 from methyl oleate, a one-step synthesis of β-bromo acrylate was accomplished by Eren et al. [14] (Scheme 2.7) from the treatment of methyl oleate with N-bromosuccinimide (NBS) and excess of acrylic acid giving bromo acrylated methyl oleate 34. A mixture of the regioisomers at C9, C10 was likely formed. Copolymerizations of BAMO with various alkenes, such as styrene (35% weight of 34), vinyl acetate, and methyl methacrylate, separately, under free-radical conditions (1.5% AIBN was used) gave the corresponding high molecular weight polymers having MW of 45,000 – 120,000 Daltons. The copolymerizations of 34 and styrene, methyl methacrylate, and vinyl acetate were carried at 80°, 65°, and 50°, respectively, for 24 hours. Copolymers 34-styrene and 34-vinyl acetate are viscous oils while 34-methyl methacrylate is soft solid. Glass transition temperatures of 34-styrene, 34-vinyl acetate, and 34-methyl methracrylate are found to be -13.5°, -17°, and -10°, respectively. The presence of bromine atom in the alkyl chain adds flame retardant property to the polymers.

Cross-linkable polyesters from plant oils utilizing lipase as a catalyst were investigated. Transparent films were produced from the hardening or curing of cross-linkable polyesters with a cobalt naphthenate catalyst. This environmentally benign process was reported by Tsujimoto et al. [15]. The polymer synthesis involved the treatment of a mixture of divinyl sebacate, glycerol and oleic/linoleic/linolenic acids all in equivalent amounts with lipase (derived from Candida antarctica) at 60° for 24 hours in a sealed tube to generate cross-linkable polyester polymers as shown in Scheme 2.8. Increases in molecular weights and yields of the polymers were found when the reactions were carried out under reduced pressure.

Scheme 2.7 Polymerization of acrylate oleic acid methyl ester 32 and bromo ester 34 with styrene.

Scheme 2.8 Synthesis of polyesters using lipase-catalyzed cross linking reaction.

These cross-linakable polymers were cured by two different methods, oxidation with catalytic amounts of cobalt naphthenate (3% by weight of the polymer) under air and thermal oxidation at 150°. In both methods, cross-linking polymers were produced after 2 hours of curing. Interestingly, the prepolymer possessing oleic acid side chain did not undergo cross-linking because of a lack of multiple double bonds in the side chain. These materials may be used in coating industries as a environmental benign and biodegradable alternatives to the petroleum based materials.

2.2.3 Polymerization of Functionalized Triglycerides

As mentioned above, triglyceride molecule contains various reactive sites. These reactive sites can be used directly or transformed into a number of polymerizable functions utilizing similar methodologies as that in the synthesis of petroleum-based polymers. The C=C bonds in triglyceride are capable of a direct polymerization through a cationic mechanism. Cationic polymerization is the mostly frequently used method towards a direct polymerization of triglycerides through carbon double bonds. Free-radical polymerization of triglycerides is rarely carried out due to the low reactivity of internal double bonds towards radicals.

A cationic copolymerization of soybean oil was reported by Larock group [16, 17] with styrene and divinylbenzene separately, and mediated by boron trifluoride diethyl etherate. Depending on the stoichiometrics of soybean oil, styrene or divinylbenzene, and BF3 used, the polymers formed range from soft rubbers to hard and tough or brittle plastic materials. Copolymers obtained from soybean oil and divinylbenzene were brittle because of their non-uniformed high cross-linking densities. The mechanical properties of the polymers, which relate to cross-linking density, apparently can be tuned by varying the amounts of comonomers such as styrene and divinylbenzene. When styrene was used as the major comonomer along with a small amount of divinylbenzene, significant improvement in mechanical properties of copolymers was achieved. These materials possess similar thermal and mechanical properties as that of industrial plastics, along with high damping and shape memory. The cationic polymerization was carried out by the addition of styrene and/or divinylbenzene to the soybean oil followed by boron trifluoride diethyl etherate, which is immiscible in the reaction medium (Scheme 2.9). The miscibility of the initiator is improved by the mixing with Norway fish oil ester resulting in a homogenous reaction. The polymerization reaction was carried out in a Teflon mold for 12 hours at 60° The increase of degree of cross linking enhances the glass transition temperature and affects the thermo-physical properties of the polymers.

Triglyceride itself is generally unreactive towards polymerization reaction (except for cationic polymerization involving a strong Lewis acid, boron trifluoride). Hence, it was converted into suitable polymerizable groups to affect the polymerization reactions. Epoxidation of the double bonds in the side chain of triglyceride is one of the most frequently used methods to convert triglycerides to polymerizable materials. Epoxidation reactions can be achieved by the treatment of MCPBA or hydrogen peroxide and acetic acid in the presence of Amberlite [18], and others. Epoxide ring opening reactions will afford either mono- or di-hydroxyl function utilizing sodium cyanoborohydride (NaBH3CN), boron trifluoride diethyl etherate in THF [19] or in methanol (giving methoxylated polyols), 1% HClO4