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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Future Trends in MODERN PLASTICS The prolific author and polymer scientist discusses the current topics in the plastics industry and recommends future research in sustainable polymers and the recycling routes of plastic waste. The book opens with a chapter discussing newly developed monomers such as alkylene-based monomers, epoxide monomers, diol-based monomers, bio-based monomers, and several other types, Modern polymerization methods are then explained, such as ionic polymerization, plasma polymerization, and ring-opening polymerization. The book moves on to special issues and some future trends in the plastics industry with recommendations for future research. Plastics have given society enormous benefits because of their versatility, light weight, durability, and low costs. However, these properties have come with negative impacts because these persistent materials are leaked into the environment during their entire life cycle. Therefore, critical chapters report on the future directions for sustainable polymers, the valorization of plastic waste, and the recovery, treatment and recycling routes of plastic waste. The book concludes with chapters on the usage of plastics in medical devices, as well as the use of plastics in restoration, food applications, additive classes, and manufacturing. Audience The book will be used by plastics engineers, chemists, polymer and materials scientists in both academia and the plastics industry.
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Seitenzahl: 421
Veröffentlichungsjahr: 2024
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Table of Contents
Cover
Table of Contents
Series Page
Title Page
Copyright Page
Preface
1 Monomers and Polymerization Methods
1.1 Types of Monomers and Synthesis Methods
1.2 Polymerization Methods
1.3 Future Trends in Summary
References
2 Automotive Industry, Hemp and Sustainable Polymers
2.1 Plastics Industry
2.2 Fields of Application
2.3 Evolution
2.4 Material Safety
2.5 Environmental Sustainability of Plastics
2.6 Future Directions for Sustainable Polymers
2.7 Circular Economy
2.8 Automotive Industry
2.9 Future Trends in Summary
References
3 Plastic Waste
3.1 Valorization of Plastic Waste
3.2 Origin of Plastic Waste
3.3 Waste Accumulation
3.4 Conversion of Plastic Waste into Fuel
3.5 Future Trends in Summary
References
4 Plastic Pollution in the Environment
4.1 Ingestion of Macroplastics by Odontocetes of the Greek Seas
4.2 Greenhouse Gas Emissions Associated with Plastics Consumption
4.3 Sustainability of Plastic Types
4.4 Plastic Industry in China
4.5 Carbon Footprint
4.6 Global Greenhouse Gas Emission from Both Traditional Plastics and Bioplastics
4.7 Future Trends in Summary
References
5 Recycling
5.1 The Frontier of Plastics Recycling
5.2 Recycling Technologies
5.3 Plastic Waste Generation
5.4 Recycled Plastics in Food Contact
5.5 Enzyme Discovery and Engineering for Sustainable Plastic Recycling
5.6 Special Compositions
5.7 Bottle Recycling
5.8 Recycling of Post-Consumer Polyolefins
5.9 Recycling of Multi-material Multilayer Plastic Packaging
5.10 Future Trends in Summary
References
6 Renewable Energy
6.1 Plastic Waste
6.2 Future Trends in Summary
References
7 Methods of Characterization
7.1 Polymer Identification Techniques
7.2 Identification of the Materials
7.3 Future Trends in Summary
References
8 Medical Uses
8.1 Optical Applications
8.2 Materials
8.3 Surgery
8.4 Polymer Implants
8.5 Orthopedic Applications
8.6 Sutures
8.7 Biomedical Uses
8.8 Drug Delivery
8.9 Self-Healing Materials
8.10 Surgical Instruments
8.11 Microplastics
8.12 Future Trends in Summary
References
9 Restoration
9.1 Deterioration of Cultural Heritage
9.2 Science
9.3 Layer-by-Layer Architectures
9.4 Future Trends in Summary
References
10 Food Applications
10.1 Molecularly Imprinted Polymers
10.2 Self-Assembled Carbohydrate Polymers
10.3 Quartz Crystal Microbalance Sensors
10.4 Analysis of Problematic Additives
10.5 Food Packaging
10.6 Food Container
10.7 Future Trends in Summary
References
11 Additive Classes
11.1 Compatibilizers
11.2 Contaminants
11.3 Legacy Additives
11.4 Chain Extenders
11.5 Nucleating Additives
11.6 Food Additives
11.7 Antioxidants
11.8 Future Trends in Summary
References
12 Manufacturing
12.1 Wood-Plastic Composites
12.2 Single-Use Plastics
12.3 Future Trends in Summary
References
Index
Acronyms
Chemicals
General Index
Also of Interest
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Monomers with one double bond.
Table 1.2 Monomers with multiple double bonds.
Table 1.3 Modern Monomers.
Table 1.4 Epoxide Monomers.
Table 1.5 Diol based monomers.
Table 1.6 Diacid based monomers.
Table 1.7 Bio-based monomers (17).
Table 1.8 Bio-Based Platforms (17).
Table 1.9 Fatty acids for fatty acid monomers.
Table 1.10 Ester-based monomers (35).
Table 1.11 Amino acids used as monomers.
Table 1.12 Monosaccharides (39).
Table 1.13 Saccharification treatment time and xylose concentration (41).
Chapter 2
Table 2.1 Applications of plastics.
Table 2.2 Common plastics used in a typical car.
Table 2.3 Natural-fiber-reinforced polymer composites.
Chapter 3
Table 3.1 Toxicants released upon open burning of various plastics.
Table 3.2 Plastic material produced in the EU in 2021 (12).
Chapter 5
Table 5.1 Methods of plastics recycling (2).
Table 5.2 Compatibility of different plastic materials (7).
Table 5.3 General properties of food packaging materials (10).
Table 5.4 Amount of migrants (11).
Table 5.5 Migration as function of time (11).
Table 5.6 Plastic-degrading enzymes (49).
Table 5.7 Materials applied for multi-material multilayer plastic packaging (8...
Chapter 8
Table 8.1 Advantages and disadvantages of contact lenses (8).
Table 8.2 Toughening agents (12).
Table 8.3 Diluents (12).
Table 8.4 Initiators and Photoinitiators (12).
Table 8.5 Advantages and disadvantages of mainstream bioprinting technology (2...
Table 8.6 Implant metal applications (37).
Chapter 9
Table 9.1 Biopolymers for multilayer architecture (30, 31).
Chapter 10
Table 10.1 Functional materials.
Table 10.2 Gas detection.
Table 10.3 Diacids for poly(amide)s (61).
Table 10.4 Diamines for poly(amide)s (61).
Table 10.5 Poly(amide) polymers (61).
Table 10.6 Polymers for food packaging (63).
Chapter 11
Table 11.1 Hazardous additives (10).
Table 11.2 Chain extenders for polyurea (15).
Table 11.3 Nucleating additives (16).
Table 11.4 Classification of non-enzymatic natural antioxidants by their mecha...
List of Illustrations
Chapter 1
Figure 1.1 Monomers with one double bond.
Figure 1.2 Monomers with multiple double bonds.
Figure 1.3 Cyclic monomers with multiple double bonds.
Figure 1.4 Apopinene.
Figure 1.5 Epoxide monomers.
Figure 1.6 Diol-based monomers.
Figure 1.7 Diacid based monomers.
Figure 1.8 Fatty acids.
Figure 1.9 Fatty acid monomer.
Figure 1.10 Tetramethyl guanidine and trifluoroacetic acid.
Figure 1.11 Amino acids used as monomers.
Figure 1.12 Monosaccharides.
Figure 1.13 Nucleobases in DNA.
Chapter 2
Figure 2.1 Pyrolysis of waste plastics (36).
Figure 2.2 Airbag apparatus (73).
Figure 2.3 Glazed plastic panel (75).
Figure 2.4 UV-absorbing materials (75).
Chapter 3
Figure 3.1 Apparatus for processing reusable fuel (28).
Figure 3.2 Apparatus for dechlorination (35).
Chapter 4
Figure 4.1 US consumption of major plastics (14).
Chapter 5
Figure 5.1 Di(2-ethylhexyl) adipate and di(2-ethylhexyl) phthalate.
Figure 5.2 Closed-loop continuous system for recycling food service ware (43).
Chapter 8
Figure 8.1 Photoinitiators.
Figure 8.2 Steroids.
Chapter 10
Figure 10.1 Quartz crystal microbalance detector assembly (15).
Figure 10.2 Galactomannan.
Figure 10.3 Diacids for Poly(amide)s (61).
Figure 10.4 Diamines for poly(amide)s (61).
Figure 10.5 Curcumin.
Chapter 11
Figure 11.1 Hazardous additives (10).
Figure 11.2 Chain Extenders for Polyurea (15).
Figure 11.3 Nucleating additive for polyurea (16).
Figure 11.4 Protein-based thickeners (23).
Chapter 12
Figure 12.1 Production process (6).
Figure 12.2 Poly(butylene adipate terephthalate).
Figure 12.3 Triethyl citrate.
Guide
Cover Page
Table of Contents
Series Page
Title Page
Copyright Page
Preface
Begin Reading
Index
Acronyms
Chemicals
General Index
Also of Interest
WILEY END USER LICENSE AGREEMENT
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Future Trends in Modern Plastics
Johannes Karl Fink
Montanuniversität Leoben, Austria
This edition first published 2024 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2024 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
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For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.
Limit of Liability/Disclaimer of WarrantyWhile the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials, or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read.
Library of Congress Cataloging-in-Publication Data
ISBN 9781394237548
Cover image: Pixabay.comCover design by Russell Richardson
Preface
This book focuses on the issues concerning future trends in plastics.
The book begins with a chapter about monomers and polymerization methods. Here, newly developed monomers, such as alkylene-based monomers, epoxide monomers, diol-based monomers, bio-based monomers, and several other types, are discussed. Then, modern polymerization methods are explained, such as ionic polymerization, plasma polymerization, and ring-opening polymerization.
Then, in the next chapter, special issues and some future trends in the plastics industry are explained. Here, recommendations for future research, are also noted. Also discussed are the enormous benefits plastics have brought to society owing to their versatility, light weight, durability and low costs. However, these properties have come with negative externalities, especially because these persistent materials are leaked into the environment during their entire life cycle. Therefore, an important section is included on the future directions for sustainable polymers.
The valorization of plastic waste is an important feature of Chapter 4. Nowadays, polymers are the most versatile materials. They contain certain chemicals and additives, such as pigments, concentrates, anti-blockers, light transformers, UV-stabilizers, etc. Therefore, an in-depth analysis has been presented with respect to the recovery, treatment and recycling routes of plastic waste in Chapters 5 and 6.
The methods of characterization are detailed in Chapter 7. Here, the properties and material testing methods, such as standards, are described.
In Chapter 8, usage of plastics in medical devices are detailed. Here, the properties, requirements, and applications are presented along with a comprehensive overview of the main types of plastics used in medical device applications.
The subsequent Chapters and their subject matter are the use of plastics in restoration, food applications, additive classes and manufacturing.
The text focuses on the literature of the past decade. Beyond education, this book will serve the needs of specialists who have only a passing knowledge of the subject matter but need to know more.
How to Use This Book
Utmost care has been taken to present reliable data. Because of the vast variety of material presented here, however, the text cannot be complete in all aspects, and it is recommended that the reader study the original literature for more complete information.
The reader should be aware that mostly US patents have been cited where available, but not the corresponding equivalent patents in other countries. For this reason, the author cannot assume responsibility for the completeness, validity or consequences of the use of the material presented herein. Every attempt has been made to identify trademarks; however, there were some that the author was unable to locate.
Index
There are three indices: an index of acronyms, an index of chemicals, and a general index.
In the index of chemicals, compounds that occur extensively, e.g., “acetone,” are not included at every occurrence, but rather when they appear in an important context.
Acknowledgements
I am indebted to our university librarians, Dr. Christian Hasenhüttl, Friedrich Scheer, Christian Slamenik, and Elisabeth Groß for their support in literature acquisition. Also, many thanks to Boryana Rashkova for her nice support.
I also want to express my gratitude to all the scientists who have carefully published their results concerning the topics dealt with herein. This book could not have been otherwise compiled.
Last, but not least, I want to thank the publisher, Martin Scrivener, for his abiding interest and help in the preparation of the text. In addition, my thanks go to Jean Markovic, who made the final copyedit with utmost care.
Johannes Fink
Wiener Neustadt
December 20, 2023
1Monomers and Polymerization Methods
Several monomers are used for polymers. Most of them are old but some of them are fresh materials. Here, monomer types and monomers are given and also special methods for polymerization.
A lot of these materials are collected in books (1–6).
Monomers can be subdivided into two classes, depending on the kind of polymer that they form (7). Monomers that participate in condensation polymerization have a different stoichiometry than monomers that participate in addition polymerization. Classifications may also include (8):
Alkylene monomers
Epoxide monomers
Diols
Diacids
Amino acids
Alcohol acids
Bio-based monomers
Nucleotides
Monosaccharides
Natural monomers
Synthetic monomers
Polar monomers
Nonpolar monomers
1.1 Types of Monomers and Synthesis Methods
In this section, common monomers, both conventional and modern monomers, are shown.
1.1.1 Alkylene Monomers
Various monomer types are presented in Tables 1.1, 1.2, and 1.7 below. Also, these compounds are shown in Figures 1.1 and 1.2.
Table 1.1 Monomers with one double bond.
Compound
Compound
Ethylene
Propylene
1-Butene
1-Pentene
2-Butene
2,3-Dimethyl-1-butene
1-Pentene
2-Pentene
2-Methyl-1-butene
3-Methyl-1-butene
2-Methyl-2-butene
1-Hexene
2-Hexene
3-Hexene
2-Methyl-1-pentene
3-Methyl-1-pentene
4-methyl-1-pentene
2-Methyl-2-pentene
3-Methyl-2-pentene
4-Methyl-2-pentene
2,3-Dimethyl-1-butene
3,3-Dimethyl-1-butene
2,3-Dimethyl-2-butene
2-Ethyl-1-butene
α
-Pinene
6,6-Dimethylbicyclo[3.1.1]hept-2-ene
Table 1.2 Monomers with multiple double bonds.
Compound
Compound
Compound
ButadieneNorbornadiene
Isoprene1,5-Cyclooctadiene
ChloropreneDicyclopentadiene
Some modern alkene-based monomers are shown in Table 1.3.
1.1.1.1 Apopinene
Apopinene (6,6-Dimethylbicyclo[3.1.1]hept-2-ene), c.f. Figure 1.4, is a biorenewable monomer that can be used for ring-opening metathesis polymerization (9).
Figure 1.1 Monomers with one double bond.
Table 1.3 Modern Monomers.
Compound
Reference
Apopinene
(
9
)
6,6-Dimethylbicyclo[3.1.1]hept-2-ene
(
9
)
Bio-based acrylic monomers
(
10
)
Figure 1.2 Monomers with multiple double bonds.
Figure 1.3 Cyclic monomers with multiple double bonds.
Figure 1.4 Apopinene.
Apopinene is the most abundant monoterpene present in nature and plays a crucial role in many biological, atmospheric and industrial processes. Similar to many other readily accessed and biorenewable terpenes, α-pinene is widely used in both the fine chemical and polymer industries. The Lewis acid-catalyzed polymerization of α-pinene generates a polymer and has found a variety of uses in a plethora of industrial applications such as adhesives, plastics, and rubbers.
The high abundance, low cost, and biorenewability of α-pinene make its incorporation into additional novel materials highly desirable from the standpoint of sustainability.
One avenue that has sparked some theoretical interest is the ring-opening metathesis polymerization of α-pinene (11).
1.1.2 Epoxide Monomers
Various epoxide monomers are presented in Table 1.4. Some of these monomers are also shown in Figure 1.5.
The synthesis of functionalized polycarbonates, employing mainly propylene oxide and cyclohexene oxide, has been detailed (12). In recent years, functionalized polycarbonates have become an emerging topic with a broad scope of potential applications. The synthetic routes and properties of numerous functionalized polycarbonates synthesized from CO2 and functional epoxide monomers have been described (12).
The synthesis of polymers from renewable resources is of high interest. Polymeric epoxide networks constitute a major class of thermosetting polymers and are extensively used as coatings, electronic materials, and adhesives (13). Owing to their outstanding mechanical and electrical properties, chemical resistance, adhesion, and minimal shrinkage after curing, they are used in structural applications as well.
Most of these thermoset types are industrially manufactured from bisphenol A (BPA), a substance that was initially synthesized as a chemical estrogen (13). The awareness of BPA toxicity combined with the limited availability and volatile cost of fossil resources and the non-recyclability of thermosets implies necessary changes in the field of epoxy networks. Thus, substitution of BPA has witnessed an increasing number of studies both from the academic and industrial sides. This review presents an overview of the reported aromatic multifunctional epoxide building blocks synthesized from biomass or from molecules that could be obtained from transformed biomass.
Table 1.4 Epoxide Monomers.
Compound
Reference
Epoxy crotyl sucrose
(
14
)
Propylene oxide
(
15
)
1,2-Butylene oxide
(
15
)
2,3-Butylene oxide
(
15
)
2,3-Epoxy heptane
(
15
)
Nonene oxide
(
15
)
5-Butyl-3,4-epoxyoctane
(
15
)
1,2-Epoxy dodecane
(
15
)
1,2-Epoxy hexadecane
(
15
)
1,2-Epoxy octadecane
(
15
)
5-Benzyl-2,3-epoxy heptane
(
15
)
4-Cyclo-hexyl-2,3-epoxy pentane
(
15
)
Chlorostyrene oxide
(
15
)
Styrene oxide
(
15
)
o
-Ethylstyrene oxide
(
15
)
m
-Ethylstyrene oxide
(
15
)
p
-Ethylstyrene oxide
(
15
)
Glycidyl benzene
(
15
)
7-Oxabicyclo[4.1.0]heptane
(
15
)
Oxabicyclo[3.1.0]hexane
(
15
)
4-Propyl-7-oxabicyclo[4.1.0]heptane
(
15
)
3-Amyl-6-oxabicyclo[3.1.0]hexane
(
15
)
Figure 1.5 Epoxide monomers.
The main glycidylation routes and mechanisms and the BPA toxicity were described. Also, the main natural sources of aromatic molecules have been detailed. The various epoxy prepolymers can be organized into simple mono-aromatic di-epoxy, mono-aromatic poly-epoxy, and derivatives with numerous aromatic rings and epoxy groups (13).
1.1.3 Diol-Based Monomers
Diol-based monomers are presented in Table 1.5 and shown in Figure 1.6.
Table 1.5 Diol based monomers.
Compound
Compound
1,6-Hexanediol
1,8-Octanediol
1,10-Decanediol
Figure 1.6 Diol-based monomers.
The synthesis and characterization of variants of poly(diol fumarate) and poly(diol fumarate-co-succinate) were described. Through a Fischer esterification, α, ω-diols and dicarboxylic acids were polymerized to form aliphatic polyester comacromers. Because of the carbon-carbon double bond of fumaric acid, incorporating it into the macromer backbone structure resulted in unsaturated chains.
By choosing α, ω-diols of different lengths (1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol) and controlling the amount of fumaric acid in the dicarboxylic acid monomer feed (33, 50, and 100 mol%), nine diol-based macromer variants were synthesized and characterized for molecular weight, number of unsaturated bonds per chain, and thermal properties.
Degradation and in vitro cytotoxicity were also measured in a subset of macromers.
Macromer networks were photocrosslinked to demonstrate the ability to perform free radical addition using the unsaturated macromer backbone. Crosslinked macromer networks were also characterized for physicochemical properties (swelling, sol fraction, compressive modulus) based on diol length and amount of unsaturated bonds. A statistical model was built using data generated from these diol-based macromers and macromer networks to evaluate the impact of monomer inputs on final macromer and macromer network properties. With the ability to be modified by free radical addition, biodegradable unsaturated polyesters serve as important macromers in the design of devices such as drug delivery vehicles and tissue scaffolds. Given the ability to extensively control final macromer properties based on monomer input parameters, poly(diol fumarate) and poly(diol fumarate-co-succinate) represent an exciting new class of macromers (16).
1.1.4 Diacid-Based Monomers
Diacid-based monomers are shown in Table 1.6 and in Figure 1.7.
Table 1.6 Diacid based monomers.
Compound
Compound
2,5-Furan dicarboxylic acid
3,4-Furan dicarboxylic acid
2,3-Furan dicarboxylic acid
Adipic acid
Azelaic acid
1.1.5 Bio-based monomers
Bio-based platforms for polymers are shown in Table 1.8.
Also, the routes to some representative sustainable polymers that are synthesized from biomass feedstocks were shown (17). Natural biopolymers, including polysaccharides, lignin, lipids, polypeptides and terpenes, can be extracted from renewable biomass. Through deconstruction and conversion or fermentation, natural biopolymers can be turned into polymer precursors for sustainable polymerization. Sustainable polymers are poly(ethylene), poly(propylene), poly(ethylene 2,5-furandicarboxylate), poly(furfural alcohol), poly(hydroxyalkanoate)s, poly(lactide) and poly(butylene succinate).
Figure 1.7 Diacid based monomers.
Table 1.7 Bio-based monomers (17).
Compound
Compound
Compound
Hydroxy acids
Diacids
Diols
Diamines
Triglycerides
Fatty acids
Amino acids
Table 1.8 Bio-Based Platforms (17).
Platform
Monomer type
Polymer type
Sugar
Hydroxy acids, diacids, diols, diamines, cyclics, vinyl
Copolyesters, polyester polyols, copolyamides, poly(urethane)s, polyolefins, polyacids
Lignin
Acids, alcohols
Polyesters, polybenzoxazines
CO
2
Cyclic carbonates Polycarbonates, non-isocyanate poly(urethane)s
Vegetable oils
Triglycerides, fatty acids
Polyesters, poly(urethane)s, thermosets
Proteins
Amino acids, (macro)cyclics
Poly(amino acid)s, poly(ester urea)s, polydepsipeptides, poly(ester amide ester)s, peptoids, cationic polymers
The recent advances in the microbial production of diamines, aminocarboxylic acids, and diacids as potential platform chemicals and bio-based polyamides monomers have been described (18).
Bio-based manufacturing processes of chemicals and polymers in biorefineries using renewable resources have extensively been developed for the sustainable carbon dioxide (CO2) neutral-based industry. Bio-based diamines, aminocarboxylic acids, and diacids have been used as monomers for the synthesis of polyamides with different carbon numbers and ubiquitous and versatile industrial polymers and also as precursors for further chemical and biological processes to afford valuable chemicals.
These platform biochemicals have been successfully produced by biorefinery processes employing enzymes and/or microbial host strains as main catalysts (18).
Metabolic engineering strategies of microbial consortia and optimization of microbial conversion processes, including whole cell bioconversion and direct fermentative production, have been developed.
1.1.6 Fatty Acids
Monomeric unsaturated fatty acids, which are derived from natural sources, are capable of being polymerized to the dimerized and trimerized form (19). This is usually realized by heating such unsaturated fatty acids in the presence of catalytic proportions of a mineral clay and, preferably, an acid-treated mineral clay, at temperatures in excess of about 180°C in an aqueous environment under autogenous pressure. Small amounts of water are deemed necessary for reaction to minimize the degradation of the fatty acids being treated (19).
Fatty acid monomers can be employed as reactive diluents for the polymerization of vinyl esters and polyesters (20, 21). They can improve the fracture resistance, lower the processing viscosity and reduce the volatile organic compounds that are present in the polymerization mixture.
Fatty acid monomers can be used to replace some or all of the styrene used in liquid thermosetting resins. They are excellent alternatives to styrene because of their low cost and low volatility.
Furthermore, fatty acids are derived from plant oils, and are therefore a renewable resource. Thus, not only would the use of fatty acids in liquid molding resins reduce health and environmental risks, but it also promotes global sustainability. Fatty acids and triglycerides have been used in a number of polymeric applications (20, 21).
The preparation of epoxidized and hydroxylated fatty acids has been reviewed (22–24).
Fatty acids that may be employed to synthesize fatty acid monomers are listed in Table 1.9. Some of these compounds are shown in Figure 1.8
Table 1.9 Fatty acids for fatty acid monomers.
Compound
Compound
Compound
Butyric acid
Capric acid
Caprylic acid
Lauric acid
Myristic acid
Palmitic acid
Stearic acid
Oleic acid
Linoleic acid
A polymeric composition, wherein the fatty acid monomer is a monomer of the formula, is shown in Figure 1.9.
Here, R is selected from the group consisting of a C2––C30 saturated alkyl residue, an unsaturated alkyl residue, an acetylenic alkyl residue, a hydroxyl alkyl residue, a carboxylic acid alkyl residue, a divinyl ether alkyl residue, a sulfur-containing alkyl residue, an amide alkyl residue, a methoxy alkyl residue, a keto alkyl residue, a halogenated alkyl residue, a branched methoxy alkyl residue, a branched hydroxyl alkyl residue, an epoxy alkyl residue, a fatty acyl-CoA alkyl residue, a cyclopropane alkyl residue, a cyclopentenyl alkyl residue, a cyclohexyl alkyl residue, a furanoid alkyl residue, a phenylalkanoic alkyl residue, and a lipoic alkyl residue (20, 21).
Figure 1.8 Fatty acids.
Figure 1.9 Fatty acid monomer.
1.1.7 Cyclic Fatty Acids
Cyclic fatty acid monomers have been found in frying oils used for fast foods (25).
Cyclic fatty acids can be classified into those that are naturally occurring and those that are formed in vegetable oils during heating (26). The former include cyclopropane, cyclopropene and cyclopentenyl acids. C17 and C19 cyclopropane acids are common in many bacteria, such as lactobacilli and enterobacteria; and mycolic (2-alkyl-3-hydroxy) acids, with up to about 90 carbons and one or two cyclopropane rings, occur in mycobacteria (27, 28).
Several acids with up to 26 carbons, one or two cyclopropane rings and a double bond in the 5 position were identified in an invertebrate from a deep-water lake (29). The C18 and C19 cyclopropane acids occur in varying amounts in the seed oils of some species of a few plant families, including Malvaceae and Sterculiaceae (27, 30). The cyclopropene counterparts are more widespread in these families, and cyclopentenyl acids are present in the seed oils of the family Flacourtiaceae, notably the genus Hydnocarpus (30).
Fatty acids with six-membered (31) and seven-membered rings have been characterized from the thermoacidophilic bacterium, Bacillus acidocaldarius.
1.1.8 Triglycerides
Epoxidized and acrylated triglycerides have been used as plasticizers and toughening agents (20, 21). In fact, the largest non-food use of triglycerides is the use of epoxidized soybean and linseed oils as plasticizers in poly(vinyl chloride). Epoxidized triglycerides have also been studied for their use as toughening agents in epoxy polymers.
The potential of epoxidized palm oil as plasticizer for poly(lactic acid) (PLA) was compared with commercialized epoxidized soybean oil (32). The plasticizers were melt-compounded into PLA at 3%, 5%, 10%, and 15%. As the aim was for the blends to be characterized towards packaging appropriate for food products, they were hot-pressed into 0.3 mm sheets, which is the approximate thickness of clamshell packaging. Fourier transform infrared spectroscopy confirmed the compatibility of the plasticizers with PLA. At similar loadings, epoxidized palm oil was superior in reinforcing elongation at break, thermal, and barrier properties of PLA.
The ductility of PLA was notably improved to 50.0% with the addition of 3% of epoxidized palm oil. From differential scanning calorimetry, the increase in crystallinity and the shifts in enthalpy of fusions in all plasticized blends denoted facilitation of PLA to form thermally stable α-form crystals.
The addition of epoxidized palm oil enabled PLA to become highly impermeable to oxygen, which can extend its potential in packaging an extensive range of oxygen-sensitive food (32).
1.1.9 Ester-Based Monomers
Some modern ester-based monomers are shown in Table 1.10.
The free-radical polymerization of dialkyl methylene malonate monomers using heat, UV light and peroxide has been described (33–35). Here, the monomer was prepared using traditional methods, which results in a monomer with low purity. The polymers are prepared via bulk polymerization. One would therefore not expect to be able to control polymer properties such as molecular weight and molecular weight distribution.
The polymerization of 1,1-disubstituted alkene compounds using anionic polymerization processes which are useful in the bulk polymerization of 1,1-disubstituted alkene compounds and processes which can operate at or near ambient conditions have been reported. Anionic bulk polymerizations may be initiated using a wide range of initiators, and may even be initiated by contact with certain substrates. Other bulk polymerization reactions may be initiated by UV light. However, the bulk polymerization may limit the ability to control the structure of the polymer molecules and/or to be able to easily handle the resulting polymer composition or product. These difficulties in bulk polymerization may be particularly pronounced when manufacturing large quantities of polymer, where heat transport issues may occur, especially when there may be shear heat generated by the flow of the high viscosity polymer and/or heat emitted due to the inherent exothermic nature of the polymerization.
Table 1.10 Ester-based monomers (35).
Compound
Compound
Methylene malonate
Dibutyl methylene malonate
Diethyl methylene malonate
Dihexyl methylene malonate
Dimethyl methylene malonate
Dipentyl methylene malonate
Butyl ethyl methylene malonate
Ethyl hexyl methylene malonate
Diisopropyl methylene malonate
Ethyl pentyl methylene malonate
Hexyl methyl methylene malonate
Butyl methyl methylene malonate
Diethoxyethyl methylene malonate
Dimethoxyethyl methylene malonate
Menthyl methyl methylene malonate
Methyl pentyl methylene malonate
Methyl propyl methylene malonate
Fenchyl methyl methylene malonate
Ethoxyethyl ethyl methylene malonate
Di-
N
-propyl methylene malonate
Ethyl methoxyethyl methylene malonate
Ethoxyethyl methyl methylene malonate
2-Phenylpropyl ethyl methylene malonate
Methoxyethyl methyl methylene malonate
2-Phenyl-1-propanol ethyl methylene malonate
Bulk polymerization of 1,1-disubstituted alkene compounds also present a challenge when attempting to control the structure of the polymer by including one or more comonomers. The high viscosity of the intermediate polymer may present difficulties in preparing a block copolymer, such as by sequential addition of a first monomer system followed by a second monomer system into a reaction vessel.
Other problems may arise when attempting to control the structure of a random copolymer, where the reaction rates of the different monomers differ so that the monomers are not uniformly distributed along the length of the polymer molecular.
For example, copolymers including one or more 1,1-disubstituted alkene compounds prepared by bulk polymerization are typically expected to have a generally blocky sequence distribution and/or result in polymer molecules having a broad distribution of monomer compositions. As used herein, a copolymer having a generally blocky sequence distribution of monomers may be characterized as having a blockiness index of about 0.7 or less, about 0.6 or less or about 0.5 or less, or about 0.4 or less (35).
Although solution polymerization processes have been employed in free-radical polymerization processes to better control the polymer architecture, such processes have not generally been employed for the anionic polymerization of 1,1-disubstituted alkenes. When a solution polymerization system is employed with anionic polymerization methods, sub-ambient temperatures (e.g., less than 10°C, less than 0°C, or less than -20°C) are typically required to control the reaction. As such, in solution polymerization systems it may be necessary to use a cooling system and/or insulation for achieving and/or maintaining such a low reaction temperature. Additional difficulties in the polymerization of 1,1-disubstituted alkene compounds arise from the possibility of the anionic group of the growing polymer reacting with an acid, thereby terminating the reaction. Therefore, using an acid in polymerizing 1,1-disubstituted alkene compounds using anionic polymerization should be avoided.
Prior attempts at anionic polymerization processes for 1,1-disubstituted alkene compounds generally have had the following drawbacks (35):
Requirement that the systems have low polymer concentrations,
Have lacked the reproducibility for controlling molecular weight distribution, or
have undesirable reactant by-products.
So, there is a need for polymerization methods, systems, and resulting polymer compositions or products that allow an improved control of one or more of the following properties of a polymer containing one or more 1,1-disubstituted alkene compounds (35):
The weight average molecular weight,
The number average molecular weight,
The polydispersity index,
The zero-shear viscosity of the polymer,
The viscosity of the polymer system.
There is also a need for a polymerization process, which can be scaled-up to a reactor of about 20 l or more, or having a throughput of about 10 kg h−1 or more. There is also a need for processes that result in a solution containing the polymer. Such solutions may be useful for applications such as paints, coatings, finishes, polishes, and adhesives (35).
It has been found that a monomer including a 1,1-disubstituted alkene can be anionically polymerized using a solution polymerization process to controllably produce polymers (e.g., to produce polymers having controlled molecular weight and/or structure).
In this solution polymerization process, the monomers are diluted by a solvent and the monomer and solvent form a single continuous phase. During the polymerization process the resulting polymer may be soluble in the solvent, or may precipitate from the solvent (35).
An example of the preparation may run as follows (35):
Preparation 1–1: Fenchyl-methyl methylene malonate is polymerized in solution. The solvent is tetrahydrofuran. A round-bottom flask is charged with about 9.0 g of tetrahydrofuran and about 1.0 g of the fenchyl-methyl methylene malonate. The mixture is stirred with a magnetic stirrer for about 5 min. Tetramethyl guanidine (TMG) is then added to the flask to activate the polymerization reaction. The molar ratio of monomer (fenchyl-methyl methylene malonate) to activator (tetramethyl guanidine) is about 1000 (i.e., 1000:1). The polymerization reaction is continued for about 1 h at a temperature of about 23°C. The polymerization process is monitored by taking small aliquots of solution and quenching the reaction in the aliquot by adding an acid. After the 1 h polymerization, a molar excess of trifluoroacetic acid (TFA) is added to the flask to quench the polymerization reaction. An aliquot of the solution is taken and characterized by NMR spectroscopy. Another aliquot of the solution is analyzed by gel permeation chromatography to measure the molecular weight distribution. The solution is then precipitated in cold (0°C) methanol. The polymer precipitates as a white powder. The precipitated polymer is filtered, dried and then characterized using differential scanning calorimetry. NMR spectroscopy at the end of the reaction shows no measurable presence of residual monomer.
The GPC indicates that the polymer has a first peak in molecular weight at about 2000 and a second peak in molecular weight at about 60,000. The polymer has a polydispersity index of about 1.43. The glass transition temperature of the polymer is about 151°C. In the homopolymerization of fenchyl-methyl methylene malonate, by varying the reaction conditions, the purity of the monomer, the activator concentration and the reaction temperature, the molecular weight distribution of the polymer may be varied between about 1 to 8 and glass transition of the polymer may be increased to be as high as about 190°C (e.g., when weight average molecular weight is high).
Tetramethyl guanidine and trifluoroacetic acid are shown in Figure 1.10.
Figure 1.10 Tetramethyl guanidine and trifluoroacetic acid.
1.1.10 Amino Acids
Amino acids have emerged as a sustainable source for the design of functional polymers (36). Besides their wide availability, their high degree of biocompatibility makes them especially appealing for a broad range of applications in the biomedical research field. In addition to these favorable characteristics, the versatility of reactive functional groups in amino acids (i.e., carboxylic acids, amines, thiols, and hydroxyl groups) makes them suitable starting materials for various polymerization approaches, which include step- and chain-growth reactions (36).
Amino acids that can be used as monomers are presented in Table 1.11. Some of these compounds are also shown in Figure 1.11.
Table 1.11 Amino acids used as monomers.
Compound
Reference
8-Amino-2-quinolinecarboxylic acid
(
37
)
2,6-Diaminopyridine
(
37
)
2,6-Pyridinedicarboxylic acid
(
37
)
7-Amino-8-fluoro-2-quinolinecarboxylic acid
(
37
)
1,8-Diaza-9-fluoro-2,7-anthracenedicarboxylic acid
(
37
)
2-(4-Aminocyclohexyl)ethanoic acid
(
38
)
4(4-Aminocyclohexyl)butanoic acid
(
38
)
4-(Aminomethyl)cyclohexanecarboxylic acid
(
38
)
4-(2-Aminoethyl)cyclohexanecarboxylic acid
(
38
)
1.1.11 Monosaccharides
Monosaccharides are shown in Table 1.12. Some monosaccharides are also shown in Figure 1.12.
Table 1.12 Monosaccharides (39).
Compound
Compound
Compound
Compound
Compound
Allose
Altrose
Glucose
Mannose
Gulose
Idose
Galactose
Talose
Psicose
Fructose
Sorbose
Tagatose
Arabinose
Lyxose
Ribose
Xylose
Ribulose
Xylulose
Figure 1.11 Amino acids used as monomers.
Figure 1.12 Monosaccharides.
A monosaccharide monomer may also be used as a mixture of several monosaccharide monomers. Furthermore, the copolymer can be prepared by using one or more diol monomers, such as octane-1,3-diol, cis-oct-5-ene-1,3-diol, isosorbide, 1,3-propanediol, 1,2-propanediol, and 1,4-butanediol (39).
Isosorbide is a bicyclic chemical compound from the group of diols and the oxygen-containing heterocycles containing two fused furan rings (40). The starting material for isosorbide is D-sorbitol, which is obtained by catalytic hydrogenation of D-glucose, which is in turn produced by hydrolysis of starch. Isosorbide is a plant-based platform chemical from which biodegradable derivatives of various functionality can be obtained.
A method for the production of monosaccharides from biomass has been described (41). In the first step, a raw material biomass is pretreated in 65 to 85% sulfuric acid at a temperature of 30°C to 70°C. In the second step, the product from the first step is subjected to a saccharification treatment in 20% to 60% sulfuric acid at a temperature of 40°C to 100°C. In detail, the method runs as follows (41):
First, 700 g of pine chips (coniferous tree) with a moisture content of 9.1% and containing 414 g of holocellulose and 1100 g of 71.5% sulfuric acid were charged in a mixing stirrer having a reactor volume of 10 l, followed by carrying out the pretreatment of the first step for 40 min at 50°C. The determination of the amount of sulfuric acid based on 100% conversion yielded a value of 786.5 g. Subsequently, hot water was charged in the reactor to dilute the sulfuric acid concentration to 30% followed by carrying out the saccharification treatment of the second step for 90 min at 85°C. At this time, in order to investigate the degree of degradation of xylose present in the saccharification treatment liquid (i.e., second step treatment product), the concentration of xylose was measured every 10 min using a high-performance liquid chromatograph. The relationship between saccharification treatment time and xylose concentration is shown in Table 1.13.
Based on the results of Table 1.13, since the xylose concentration was nearly constant, a reduction in the amount of xylose during saccharification treatment attributable to degradation was not observed. Next, the saccharification treatment liquid was cooled to about 40°C, and the filtration procedure of the second step was carried out.
Table 1.13 Saccharification treatment time and xylose concentration (41).
Reaction time
min
Xylose concentration % by weight
10
0.30
20
0.38
30
0.43
40
0.45
50
0.48
60
0.51
70
0.51
80
0.52
90
0.50
The monosaccharide concentration of the resulting filtrate was measured using the aforementioned high-performance liquid chromatograph (HPLC). The amount of monosaccharide contained in the filtrate was calculated using the following equation based on that value and the total amount of liquid.
The amount of monosaccharides such as glucose, xylose and mannose, contained in the filtrate was 249 g after the saccharification treatment. The determination of the conversion rate of holocellulose to monosaccharides based on the weight of the holocellulose from the amount of monosaccharides yielded a value of 60.1%.
The concentration of sulfuric acid in this effluent saccharification liquid (raffinate) was 1.0% by weight. The monosaccharification treatment of the third step was then carried out on this effluent saccharification liquid (raffinate) using an autoclave by holding at a temperature of 121°C for 30 min.
Then, the sugar liquid was collected and the monosaccharide concentration in the sugar liquid was again measured using the aforementioned high-performance liquid chromatograph (HPLC) to calculate the amount of monosaccharides.
As a result, the amount of monosaccharides in the sugar liquid was 312 g (41).
1.1.11.1 Properties of Monosaccharides
The properties of monosaccharides can be found in detail in Wikipedia (42).
Allose. Allose is an aldohexose sugar. It is a rare monosaccharide that occurs as a 6-O-cinnamyl glycoside in the leaves of the African shrub Protea rubropilosa. Extracts from the fresh-water alga Ochromas malhamensis contain this sugar.
Altrose. Altrose is an aldohexose sugar. D-Altrose is an unnatural monosaccharide. L-altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.
Glucose. Glucose is a sugar with the molecular formula C6H12O6. Glucose is the most abundant monosaccharide. It is mainly made by plants and most algae during photosynthesis from water and carbon dioxide using energy from sunlight, where it is used to make cellulose in cell walls. It is the most abundant carbohydrate in the world.
Mannose. Mannose is a sugar monomer of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, in particular for the glycosylation of certain proteins.
Gulose. Gulose is an aldohexose sugar. It is a monosaccharide that is very rare in nature, but has been found in archaea, bacteria and eukaryotes. Also, it may act as a syrup with a sweet taste. It is soluble in water and slightly soluble in methanol. d-Gulose is a C-3 epimer of d-galactose and a C-5 epimer of l-mannose.
Idose. Idose is a hexose. It has an aldehyde group and is an aldose. It can be synthesized by the aldol condensation of d-glyceraldehyde and l-glyceraldehyde. l-Idose is a C-5 epimer of d-glucose.
Galactose. Galactose is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molecule linked with a glucose molecule forms a lactose molecule.
Talose. Talose s an aldohexose sugar. It is an unnatural monosaccharide. It is a C-2 epimer of galactose and a C-4 epimer of mannose.
Psicose.d-Psicose (C6H12O6), also known as d-allulose, is a low-calorie epimer of the monosaccharide sugar fructose used by some major commercial food and beverage manufacturers as a low-calorie sweetener. It was first identified in wheat in the 1940s. Actually, allulose is naturally present in small quantities in certain foods.
Fructose. Fructose is a ketonic sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed by the gut directly into the blood of the portal vein during digestion. The liver then converts both fructose and galactose into glucose, so that dissolved glucose, known as blood sugar, is the only monosaccharide present in circulating blood.
Sorbose. Sorbose is a ketose. It has a sweetness that is equivalent to sucrose (table sugar). The commercial production of vitamin C (ascorbic acid) often begins with sorbose. l-Sorbose is the configuration of the naturally occurring sugar. It can be prepared from O-benzylglucose.
Tagatose. Tagatose is a hexose monosaccharide. It is found in small quantities in a variety of foods. Therefore, it has attracted attention as an alternative sweetening agent. It is often found in dairy products, because it is formed when milk is heated. It is similar in texture and appearance to sucrose. Since it is metabolized differently from sucrose, tagatose has a minimal effect on blood glucose and insulin levels. Tagatose is also approved as a tooth-friendly ingredient for dental products. The consumption of more than about 30 gof tagatose in a dose may cause gastric disturbances, as it is mostly processed in the large intestine, similar to soluble fiber.
Arabinose. Arabinose is an aldopentose, a monosaccharide containing five carbon atoms, and including an aldehyde functional group.
For biosynthetic reasons, most saccharides are almost always more abundant in nature as the d-form, or structurally analogous to d-glyceraldehyde. However, l-arabinose is in fact more common than d-arabinose in nature and is found in nature as a component of biopolymers such as hemicellulose and pectin.
Lyxose. Lyxose is an aldopentose, a monosaccharide containing five carbon atoms, and with an aldehyde functional group. Lyxose occurs only rarely in nature, for example, as a component of bacterial glycolipids.
Ribose. Ribose is a simple sugar and carbohydrate with molecular formula C5H10O5. The naturally-occurring form, d-ribose, is a component of the ribonucleotides from which RNA is built.
Xylose. Xylose is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is derived from hemicellulose, one of the main constituents of biomass. Like most sugars, it can adopt several structures depending on conditions. With its free aldehyde group, it is a reducing sugar.
Ribulose. Ribulose is a ketopentose, a monosaccharide containing five carbon atoms, including a ketone functional group. It has chemical formula C5H10O5. Two enantiomers are possible, d-ribulose (d-erythro-pentulose) and l-ribulose (l-erythro-pentulose). d-Ribulose is the diastereomer of d-xylulose.
Ribulose sugars are composed in the pentose phosphate pathway from arabinose. They are important in the formation of many bioactive substances. As the 1,5-bisphosphate, d-ribulose combines with carbon dioxide at the start of the photosynthesis process in green plants (carbon dioxide trap). Ribulose has the same stereochemistry at carbons 3 and 4 as the five-carbon aldoses ribose and arabinose.
Xylulose. Xylulose is a ketopentose, a monosaccharide containing five carbon atoms, and including a ketone functional group. It has the chemical formula C5H10O5. In nature, it occurs in both the l- and d-enantiomers. 1-Deoxyxylulose is a precursor to terpenes via the DOXP pathway.
1.1.12 Nucleotides
Nucleotides are organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate (43). They serve as monomeric units of the nucleic acid polymers; deoxyribonucleic acid and ribonucleic acid. Both of these are essential biomolecules within all life forms on Earth. Nucleotides are obtained in the diet and are also synthesized from common nutrients by the liver.
Nucleotides are composed of three subunit molecules (43):
A nucleobase,
A five-carbon sugar (ribose or deoxyribose), and
A phosphate group consisting of one to three phosphates.
The four nucleobases in deoxyribonucleic acid are guanine, adenine, cytosine and thymine; in RNA, uracil is used in place of thymine. These compounds are shown in Figure 1.13
Figure 1.13 Nucleobases in DNA.
Nucleotides also play a central role in metabolism at a fundamental, cellular level. They provide chemical energy in the form of the nucleoside triphosphates, adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP) and uridine triphosphate (UTP) throughout the cell for the many cellular functions that demand energy, including amino acid, protein and cell membrane synthesis, moving the cell and cell parts (both internally and intercellularly), and cell division. In addition, nucleotides participate in cell signaling (cyclic guanosine monophosphate or cGMP and cyclic adenosine monophosphate or cAMP), and are incorporated into important cofactors of enzymatic reactions (e.g., coenzyme A, FAD, FMN, NAD, and NADP+) (43).
1.2 Polymerization Methods
1.2.1 Anionic Polymerization
Anionic polymerization is a form of chain-growth polymerization or addition polymerization that involves the polymerization of vinyl monomers initiated with anions. The type of reaction has many manifestations, but traditionally vinyl monomers are used. Often anionic polymerization involves living polymerization, which allows control of the final structure of the polymer.
1.2.2 Cationic Polymerization
Cationic polymerization is a type of chain-growth polymerization where a cationic initiator transfers an electric charge to a monomer which then becomes reactive.
This reactive monomer goes on to react similarly with other monomers to form a polymer. The types of monomers necessary for cationic polymerization are limited to alkenes with electron-donating substituents and heterocycles.
Similar to anionic polymerization reactions, cationic polymerization reactions are very sensitive to the type of solvent used. Specifically, the ability of a solvent to form free ions will dictate the reactivity of the propagating cationic chain.
1.2.3 Plasma Polymerization
Plasma polymerization (or glow discharge polymerization) uses plasma sources to generate a gas discharge that provides energy to activate or fragment gaseous or liquid monomer, often containing a vinyl group, in order to initiate polymerization. The polymers that are formed from this technique are generally highly branched and highly crosslinked, and adhere to solid surfaces well.
The biggest advantage to this process is that polymers can be directly attached to a desired surface while the chains are growing.
1.2.4 Ring-Opening Polymerization
Ring-opening polymerization is a form of chain-growth polymerization in which the terminus of a polymer chain attacks cyclic monomers to form a longer polymer. The reactive center can be radical, anionic or cationic.
Some cyclic monomers, such as norbornene or cyclooctadiene, can be polymerized to high molecular weight polymers by using metal catalysts. Ring-opening polymerization is a versatile method for the synthesis of biopolymers.
Ring-opening of cyclic monomers is often driven by the relief of bond-angle strain. Thus, as is the case for other types of polymerization, the enthalpy change in ring-opening is negative.
1.2.4.1 Monomers
Cyclic monomers that are amenable to ring-opening polymerization include epoxides, cyclic trisiloxanes, some lactones, lactides, cyclic carbonates, and amino acid N-carboxyanhydrides. Many strained cycloalkenes, such as norbornene, are suitable monomers via ring-opening metathesis polymerization.
1.3 Future Trends in Summary
This chapter explained monomers.
In addition, newly developed monomers, such as alkylene-based monomers, epoxide monomers, diol-based monomers, bio-based monomers, and several other types were discussed. Then, modern polymerization methods were explained, such as ionic polymerization, plasma polymerization, and ring-opening polymerization.
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