Hairy Nanoparticles E-Book
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- Herausgeber: Wiley-VCH GmbH
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
The book covers comprehensive information of hairy nanoparticles in terms of their synthesis, dynamics and self-assembly, interfacial, thermal, and rheological properties, functionalities, and applications.
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Seitenzahl: 893
Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Title Page
Copyright
Preface
1 Synthesis of Hairy Nanoparticles
1.1 Introduction to Grafting Chemistry
1.2 Surface Functionalization of Nanoparticles
1.3 Synthesis of Hairy Nanoparticles
1.4 The Role of “Architecture” in Hairy Nanoparticles
1.5 Conclusion
Acknowledgment
References
2 Hairy Nanoparticles via Self-assembled Linear Block Copolymers
2.1 Introduction
2.2 Hairy NPs via Bulk Microphase Separation of Block Copolymers
2.3 Hairy NPs via the Self-assembly of Block Copolymer in Solution
2.4 Summary
References
3 Hairy Nanoparticles via Unimolecular Block Copolymer Nanoreactors
3.1 Background
3.2 Synthesis and Properties of Block Copolymer Unimolecular Micelles
3.3 Synthesis of Monodispersed Nanoparticles via Block Copolymer Unimolecular Micelles Nanoreactors
3.4 Application of Polymer-Capped Nanoparticles
3.5 Conclusions and Perspectives
References
4 Environmentally Responsive Hairy Inorganic Particles
4.1 Introduction
4.2 Environmentally Responsive Well-defined Binary Mixed Homopolymer Brush-grafted Silica Particles
4.3 Thermoresponsive Polymer Brush-grafted Silica Particles
4.4 Summary and Outlook
Acknowledgements
References
5 Self-Assembly of Hairy Nanoparticles with Polymeric Grafts
5.1 Introduction
5.2 Self-Assembly of PGNPs into Colloidal Molecules
5.3 Self-Assembly of PGNPs Into One-Dimensional (1-D) Structures
5.4 Self-Assembly of PGNPs into 2-D Structures
5.5 Self-Assembly of PGNPs into 3-D Structures
5.6 Representative Applications of Assembled PGNPs
5.7 Summary and Outlook
References
Note
6 Interfacial Property of Hairy Nanoparticles
6.1 Introduction
6.2 Hairy NPs as Interfacial Building Blocks
6.3 Hairy NPs Assembly at Various Interfaces
6.4 Interfacial Entropy
6.5 Interfacial Jamming
6.6 Single-Chain NPs at Interfaces
References
7 Hairy Hollow Nanoparticles
7.1 Introduction
7.2 Overview of the Progress in the Design and Synthesis of Hairy Hollow NPs
7.3 Conclusions and Perspectives
Acknowledgment
References
8 Self-Assembly of Binary Mixed Homopolymer Brush-Grafted Silica Nanoparticles
8.1 Introduction
8.2 Computer Simulations of the Self-Assembled Morphology of MBNPs
8.3 Self-Assembled Morphologies of Well-Defined Binary Mixed Homopolymer Brushes Grafted on Silica NPs
8.4 Self-Assembled Morphology in Solvents and Homopolymer Matrices
8.5 Conclusions and Future Work
Acknowledgment
References
9 Hairy Plasmonic Nanoparticles
9.1 Introduction
9.2 Plasmonic Properties of Isolated NPs and Energy Transfer to Adjacent Hairy Environment
9.3 Plasmonic Coupling Scenarios of Hairy Plasmonic NPs
9.4 Summary and Outlook Discussions
Acknowledgments
References
10 Hairy Metal Nanoparticles for Catalysis: Polymer Ligand-Mediated Catalysis
10.1 Nanocatalysis Mediated by Surface Ligands
10.2 Catalysis Mediated by PGNPs with Thiol-Terminated Polymers
10.3 Catalysis Mediated by PGNPs with NHC-Terminated Polymers
10.4 Other PGNP Nanocatalysts
10.5 Conclusion and Outlook
References
11 Hairy Inorganic Nanoparticles for Oil Lubrication
11.1 Introduction
11.2 Oil-Soluble Poly(lauryl methacrylate) Brush-Grafted Metal Oxide NPs as Lubricant Additives
11.3 Effects of Alkyl Pendant Groups on Oil Dispersibility, Stability, and Lubrication Property of Poly(alkyl methacrylate) Brush-Grafted Silica Nanoparticles
11.4 Improved Lubrication Performance by Combining Oil-Soluble Hairy Silica Nanoparticles and an Ionic Liquid as Additives for PAO-4
11.5 Upper Critical Solution Temperature (UCST)-Type Thermoresponsive Poly(alkyl methacrylate)s in PAO-4
11.6 Summary
Acknowledgments
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Surface anchoring groups and applicable surfaces.
Table 1.2 Summary of polymer-grafted metal oxide nanoparticles synthesized ...
Chapter 9
Table 9.1 Isolated and coupled plasmonic NP systems and selected functional...
Chapter 10
Table 10.1 Summary of 4-NP reduction catalyzed by other PGNPs.
Chapter 11
Table 11.1 Characterization data for hairy silica nanoparticles and corresp...
Table 11.2 Wear volumes for iron flats and steel balls from tribological te...
List of Illustrations
Chapter 1
Scheme 1.1 Surface-initiated polymerization from pulsed plasma deposited ha...
Scheme 1.2 Synthesis of oSiO
2
nanoparticles.
Scheme 1.3 The “grafting-from” approach.
Scheme 1.4 General scheme for SI-ATRP.
Figure 1.1 Illustration of equilibrium of typical RDRP techniques.
Figure 1.2 Top scheme: synthesis of BiBADA and surface functionalization of...
Figure 1.3 External control for various ATRP techniques.
Figure 1.4 Three main approaches to surface RAFT polymerization: (a) Using ...
Scheme 1.5 The “grafting-onto” approach.
Scheme 1.6 The “ligand exchange” approach.
Figure 1.5 Reaction scheme for the synthesis of photo-crosslinked stable PH...
Scheme 1.7 Synthesis of hairy nanoparticles/nanorods through (a) star polym...
Scheme 1.8 Schematic representation of the advanced application of hairy na...
Figure 1.6 Illustration of the transition from concentrated particle brush ...
Scheme 1.9 Schematic representation of the architecture of the grafted chai...
Scheme 1.10 Synthesis of hairy nanoparticles with different grafting densit...
Figure 1.7 Representative bright-field transmission electron micrographs fo...
Scheme 1.11 Interactions of hairy nanoparticles with bimodal molecular weig...
Figure 1.8 TEM images of monolayers (a–e), crack formation (f–j), and illus...
Figure 1.9 TEM images of bimodal SiO
2
-
g
-PMMA-
b
-PS hairy nanoparticles. (a, ...
Chapter 2
Figure 2.1 Schematic diagram of various bulk microphase separation morpholo...
Figure 2.2 Schematic diagram of the phase interface distribution of diblock...
Figure 2.3 (a) Using PS-
b
-PI diblock copolymer as the model polymer, the th...
Figure 2.4 Thermodynamic phase diagrams drawn from the experimental results...
Figure 2.5 The microphase separation structure of ABC triblock copolymer pr...
Figure 2.6 Schematic diagram of the preparation of hairy NPs with different...
Figure 2.7 TEM results of NPs with different shapes prepared from PTEPM-
b
-P...
Figure 2.8 TEM results of hairy NPs prepared by bulk microphase separation ...
Figure 2.9 TEM results of samples obtained from methanol dispersions of nan...
Figure 2.10 TEM characterization of NPs obtained by microphase separation o...
Figure 2.11 PtBMA
227
-
b
-PS
187
block copolymer bulk microphase separation sam...
Figure 2.12 (a) TEM image and structural schematic diagram of Janus nanoshe...
Figure 2.13 TEM images of core-cross-linked porous nanosheets prepared from...
Figure 2.14 Transmission electron microscope and corresponding schematic di...
Figure 2.15 The effect of SDS content on the aggregation morphology of PS
31
...
Chapter 3
Figure 3.1 (a) Different behaviors of unimolecular nanoreactors and supramo...
Figure 3.2 The chemical structures and parameters of common cyclodextrins....
Figure 3.3 Synthetic strategy for unimolecular polymeric core@shell and hol...
Figure 3.4 Schematic representation of synthesis of cellulose-
g
-[poly(acryl...
Figure 3.5 Schematic representation of synthetic strategies for nanoparticl...
Figure 3.6 Scheme illustration of the synthesis of nanoparticles via the st...
Figure 3.7 Light-enabled reversible self-assembly of Au NPs intimately and ...
Figure 3.8 Synthetic strategy for magnetic/plasmonic Fe
3
O
4
@Au core@shell na...
Figure 3.9 Synthetic route to hairy hollow plasmonic nanoparticles (i.e. PS...
Figure 3.10 (a, c) TEM image and (b, d) XRD profile of PbTe HNPs capped wit...
Figure 3.11 (a) Plot surface of AFM image of TiO
2
templated by P1. (a) befo...
Figure 3.12 Schematic representation of synthesis strategies for TiO
2
nanor...
Figure 3.13 Scheme (a) Preparation of spherical superparamagnetic Fe
3
O
4
col...
Figure 3.14 Illustration of the designed process
in situ
synthesis of the A...
Figure 3.15 Three routes to nanorods.
Figure 3.16 Synthetic strategies for 1D nanocrystals, using amphiphilic cyl...
Figure 3.17 Synthesis of the hydrophilic bottlebrush-like HPC-
g
-PAA polymer...
Figure 3.18 (a) Schematic diagram for the synthesis of hairy PR and its use...
Figure 3.19 (a) Energy levels and charge-transfer processes in perovskite s...
Figure 3.20 (a) TEM and (b) HRTEM images of ZnFe
2
O
4
/carbon nanocomposites. ...
Figure 3.21 Catalytic performance of Au@TiO
2
core@shell nanoparticles with ...
Chapter 4
Scheme 4.1 Schematic illustration for the synthesis of hairy particles by “...
Scheme 4.2 Simplified schematic illustration of self-assembly of binary mix...
Scheme 4.3 Synthesis of well-defined mixed homopolymer brushes by sequentia...
Scheme 4.4 Synthesis of well-defined mixed poly(
tert
-butyl acrylate)/polyst...
Scheme 4.5 Synthesis of a surface-immobilizable monochlorosilane-functional...
Figure 4.1 Plot of ln[M]
0
/[M] versus time for the kinetic analysis of ATRP ...
Figure 4.2 A Tyndall light scattering experiment shows the stable dispersio...
Figure 4.3
1
H NMR spectra of mixed PAA/PS brush particles dispersed in (a) ...
Figure 4.4 Bright-field TEM micrographs of (a) a top view and (b) a cross-s...
Figure 4.5 Bright-field TEM micrograph of mixed P
t
BA/PS brush-grafted 180 n...
Figure 4.6 Bright-field TEM images of mixed P
t
BA/PS brush-grafted 160 nm si...
Figure 4.7 TEM images of mixed P
t
BA/PS brush-grafted silica particles with ...
Scheme 4.6 Molecular structures of methoxydi(ethylene glycol) methacrylate ...
Figure 4.8 Average hydrodynamic diameter of PTEGMMA brush-grafted silica pa...
Figure 4.9 (a) Optical photos of the initial state of the aqueous (bottom)/...
Scheme 4.7 Schematic illustration of phase transfer of thermosensitive PTEG...
Figure 4.10 Transfer temperature of thermoresponsive polymer brush-grafted ...
Figure 4.11 Plots of (a) the transfer temperature (
T
tr
) of P(TEGMMA-
co
-MAA)...
Figure 4.12 Phase transfer of thermo- and pH-sensitive P(TEGMMA-
co
-MAA) hai...
Scheme 4.8 Synthesis of PDEGMMA-
b
-P(DEGMMA-
co
-TMAEMA-I) brush-grafted silic...
Figure 4.13 Average apparent hydrodynamic size
D
h
, obtained from DLS study ...
Figure 4.14 Optical photos of a 6.0 wt % aqueous dispersion of P(TMAEMA-I)-
Figure 4.15 Plots of dynamic storage modulus
G
′ and loss modulus
G
″ of a 6....
Figure 4.16 Plots of dynamic storage modulus
G
′ and loss modulus
G
′′ (left ...
Scheme 4.9 Stepwise formation of a 3-D network hydrogel by a doubly thermos...
Scheme 4.10 Synthesis of doubly thermosensitive ABC linear triblock copolym...
Figure 4.17 Plots of dynamic storage modulus
G
′ versus temperature for (A) ...
Figure 4.18 Plots of (a) average
G
′
max
from three heating ramps and (b) ave...
Chapter 5
Figure 5.1 The generation of patchy nanospheres through the phase segregati...
Figure 5.2 Self-assembly of PGNPs with anisotropic core into CMs. (a–c) Sel...
Figure 5.3 Directly self-assembly of nanospheres grafted with different pol...
Figure 5.4 Self-assembly of binary PGNPs into CMs. (a) Schematic illustrati...
Figure 5.5 Alternating polymerization of nanocopolymers into linear nanostr...
Figure 5.6 Self-assembly of polymer-tethered NRs in selective solvents. (a)...
Figure 5.7 Colloidal polymer chains driven by dipolar interactions. (a) Sch...
Figure 5.8 Confined self-assembly of PGNPs assisted by hard template. (a) C...
Figure 5.9 Self-assembly of PGNPs templated by supramolecular copolymer ass...
Figure 5.10 1-D assembled structures assisted by some special soft template...
Figure 5.11 One-dimensional structures assembled in polymer thin-film throu...
Figure 5.12 Self-assembly of PGNPs using BCPs as templates. (a-b) TEM image...
Figure 5.13 (a) Schematic illustration of the assembly of PS-grafted AuNRs ...
Figure 5.14 2-D structures assembled on substrate assisted by hard template...
Figure 5.15 2-D structures from interfacial assembly. (a) Illustration show...
Figure 5.16 (a) TEM images of P2VP-AuNRs in P2VP films as a function of nan...
Figure 5.17 (a–c) TEM images of two-dimensional PDMS-modified 9.5 nm-Fe
2
O
3
...
Figure 5.18 Self-assembly of binary PGNPs. (a–b) Structure formation in the...
Figure 5.19 Clustering of PGNPs based on hydrophobic interaction. (a) Schem...
Figure 5.20 Clustering of PGNPs under confinement t. (a) Top: schematic ill...
Figure 5.21 Self-assembly of M-PGNPs into vesicular structures. (a) Schemat...
Figure 5.22 Self-assembly of B-PGNPs into vesicular and tubular structures....
Figure 5.23 Co-assembly of B-PGNPs and amphiphilic BCPs into hybrid vesicle...
Figure 5.24 3-D superlattices and crystals assembled in solution. (a) SAXS ...
Figure 5.25 Structural diversity in 3-D BNSLs self-assembled from AuNPs
3.8-
...
Figure 5.26 The biological application of assemblies fabricated form differ...
Figure 5.27 The biological application of hybrid MPVe assembled from AuNPs@...
Chapter 6
Figure 6.1 (a) Conformation of the grafted polymers at hairy NPs in good so...
Figure 6.2 (a) Scaling law of polymer brush height (
h
) and molecular weight...
Figure 6.3 (a) Asymmetric geometries of hairy NPs in poor solvents. Scale b...
Figure 6.4 Patchy and Janus NPs derived from ABC triblock terpolymers in se...
Figure 6.5 (a) Wettability of homogeneous NPs at interfaces (left), and dep...
Figure 6.6 Morphology diagram of the PS-grafted SiO
2
NPs dispersed in PS ma...
Figure 6.7 (a) Mechanical properties for nanocomposites: percolated cluster...
Figure 6.8 (a) Thin film of hairy NP nanocomposite under projectile impact....
Figure 6.9 (a) Patchy and Janus hairy Au NPs.(b) Formation of AB
3
struc...
Figure 6.10 (a) Core–shell colloidosomes assembled by binary hairy Au NPs o...
Figure 6.11 (a) Polymer blends of SAN and PPE using Janus NPs as compatibil...
Figure 6.12 Schematic Au NR(PS)
n
and TEM images of different rings from the...
Figure 6.13 (a) Nanostructured coatings with sensing performance.(b) An...
Figure 6.14 (a) DNA-grafted Au NPs, and assembly on a lipid layer at air–wa...
Figure 6.15 (a) Distribution of PS-grafted Au NPs in a polystyrene thin fil...
Figure 6.16 (a) Deformation and stability of the water droplets with a jamm...
Figure 6.17 (a) Formation of a bijel by jammed Janus NPs in situ formed at ...
Figure 6.18 (a) Photo responsive interfacial jamming by host–guest recognit...
Figure 6.19 (a) SCNPs of diverse topologies covering colloid–chain, colloid...
Figure 6.20 (a) DLS and (b) GPC traces of PS
93k
-
b
-P4VP
35k
(1) and PS
93k
-
c
P4...
Figure 6.21 Single-chain-grafted NPs by fast termination of (a) anionic liv...
Figure 6.22 (a) TEM image of the Janus composite SCNP of PS-P2VP@Co-PEO by ...
Figure 6.23 TEM images of the PS-
c
PI@Ni-PEO after staining with (a) PTA and...
Figure 6.24 (a) Illustrative synthesis of the Janus composite NP of PS-
c
PAA...
Chapter 7
Figure 7.1 Schematic representation for the synthesis of polymeric hollow n...
Figure 7.2 Schematic illustration for the preparation of photo- and thermo-...
Figure 7.3 Schematic illustration for the preparation of pH-responsive holl...
Figure 7.4 Formation of a pH and temperature dual-responsive hollow nanocap...
Figure 7.5 Synthetic procedure for fabricating the NCPs.
Figure 7.6 Reaction pathway to cross-linked PCL-functionalized silica NPs (...
Figure 7.7 Schematic illustration for the preparation of well-defined unifo...
Figure 7.8 Schematic illustration of the fabrication of air@PVK-PNIPAM hair...
Figure 7.9 Schematic illustration of the synthesis of hairy metal@air@polym...
Figure 7.10 Schematic representation of the preparation of polymer capsules...
Figure 7.11 Schematic representation of the procedures used for fabricating...
Figure 7.12 The chemical structure of the diblock copolymer PI-
b
-PCEMA (abo...
Figure 7.13 (a) Preparation of
μ
-(P
t
BA)(PCEMA)(PEO)
1.14
by the “associ...
Figure 7.14 (A) Schematic representation of the triblock metallopolymer wit...
Figure 7.15 Preparation of PIEMA-
b
-PNIPAM-based hairy hollow polymer nanosp...
Figure 7.16 The synthetic route for PEG
113
-
b
-P(HPMA
320
-
co
-GlyMA
80
) diblock ...
Figure 7.17 Fabrication of hollow nanospheres from a bottlebrush copolymer ...
Figure 7.18 Chemical structure and schematic illustration of the multicompo...
Figure 7.19 Synthetic route for the core–shell bottlebrush copolymer and sc...
Figure 7.20 Synthetic pathway for the direct [4 + 2] functionalization of S...
Figure 7.21 Schematic illustration of the preparation of hairy MWNTs via SI...
Figure 7.22 Fabrication of PSPMA-
g
-HSNPs, hydration mechanism of the negati...
Figure 7.23 Synthetic route of triple-responsive HMSNs-PDEAEMA via SI-ATRP....
Figure 7.24 Schematic illustration of the preparation and surface functiona...
Figure 7.25 (a) Schematic illustration of the amphiphilic gold NP coated wi...
Figure 7.26 Stepwise representation of the synthesis of low-bandgap hairy h...
Figure 7.27 Schematic illustration of the fabrication of hairy silica hybri...
Chapter 8
Figure 8.1 (a) Simulated morphology of individual MBNPs at different grafti...
Figure 8.2 (a) Simulated morphology of individual MBNPs with asymmetric cha...
Figure 8.3 (a) Typical structures of individual MBNPs at
σ
B
/
σ
A
= ...
Figure 8.4 (a) Schematic representation of the assembly of MBNPs. (b) Self-...
Scheme 8.1 Synthesis of well-defined binary mixed homopolymer bushes from a...
Figure 8.5 Bright-field TEM micrographs of self-assembled (a)
MBNP-I-1
and ...
Scheme 8.2 Synthesis of P
t
BA/PS
MBNP-II
with a fixed P
t
BA M
n
and various PS...
Figure 8.6 Bright-field TEM micrographs of (a)
MBNP-II
-
1
(P
t
BA M
n
= 24.5 kD...
Scheme 8.3 Schematic illustration of morphologies of P
t
BA/PS
MBNP-II
with a...
Figure 8.7 Bright-field TEM micrographs of (a)
MBNP-III
-
1
(P
t
BA M
n
= 18.6 k...
Figure 8.8 (left) Synthesis of mixed P
t
BA/PS brushes with varying overall g...
Figure 8.9 Bright-field TEM micrographs of mixed P
t
BA/PS brush-grafted 172 ...
Figure 8.10 Plot of log
D
N
versus log
σ
overall
, where
D
N
is the normaliz...
Figure 8.11 Bright-field TEM micrographs of (a)
MBNP-V-1
: P
t
BA M
n
= 13.3 kD...
Figure 8.12 Plots of log
D
versus log(MW) for various
MBNP-V
samples cast fr...
Figure 8.13 Bright-field TEM micrographs (A and B) of mixed P
t
BA/PS brush-g...
Figure 8.14 Bright-field TEM micrographs of one (a) P
t
BA-grafted silica NP,...
Figure 8.15 (a) Bright-field TEM micrograph of a dense monolayer film of 67...
Figure 8.16 (a–i) Consecutive z-scan TEM images of the 3D-reconstructed box...
Figure 8.17 Schematic illustration of a dense monolayer of mixed P
t
BA/PS br...
Figure 8.18 (a, d) Bright-field 2D TEM images and (b, e) top-view and (c, f...
Figure 8.19 (a–d) Bright-field TEM micrographs of
MBNP-I-3
cast from DMF, a...
Figure 8.20 Cryo-TEM micrographs of PAA/PS
MBNP-VI-4
in frozen (a, b) DMF a...
Figure 8.21 (a, c) Bright-field TEM micrographs of P
t
BA/PS
MBNP-VI-2
in the...
Figure 8.22 (a) Bright-field TEM micrograph of P
t
BA/PS
MBNP-VI-2
in the 65 ...
Figure 8.23 (a, c, e) Bright-field TEM micrographs of P
t
BA/PS
MBNP-VI-2
in ...
Figure 8.24 Schematic illustrations of (a) wet-brush regime, (b) dry-brush ...
Chapter 9
Figure 9.1 An overview about the potential of hairy plasmonic nanoparticles...
Figure 9.2 (a) Introduction to hairy plasmonic nanoparticles by a simplifie...
Figure 9.3 (a) TEM image of polystyrene-grafted gold nanocubes with differe...
Figure 9.4 (a) Relative temperature increase calculated as a result of phot...
Figure 9.5 Near-field promoted energy transfer to the environment. (a) The ...
Figure 9.6 Left: Planet–satellite-type plasmonic clusters assembled via sta...
Figure 9.7 Selective attachment of satellite particles to the tips of NRs (...
Figure 9.8 TEM tilt series emphasizing helical assemblies of AuNRs coated w...
Figure 9.9 Top row: TEM images of self-assembled layers of poly(
N
-isopropyl...
Figure 9.10 (a) SEM image of parallel gold NP (77 nm) double lines assemble...
Chapter 10
Scheme 10.1 Scheme to illustrate the PGNPs with different types of polymer ...
Figure 10.1 (a, d) Schemes to show the catalytic conversion of 4-NP to 4-AP...
Figure 10.2 (a) Chemical structures of AuNPs grafted by PMA. (b) Plotting t...
Figure 10.3 TEM images to show AuNPs (a) before and (b) after surface modif...
Figure 10.4 Synthesis of the two PS NHC precursors from bromide-terminated ...
Figure 10.5 (a) Scheme and images to show the PGNPs prepared with PS
40
-bica...
Figure 10.6 The retention of the ECSA of AuNPs under electrolysis at −0.9 V...
Figure 10.7 (a) Chemical structures of polymeric and small molecular ligand...
Figure 10.8 (a) Schematic illustration on the thermosresponsiveness of AuNP...
Chapter 11
Scheme 11.1 (a) Schematic of the Stribeck curve for the lubrication regimes...
Scheme 11.2 Schematic illustration for the preparation of hairy nanoparticl...
Figure 11.1 Bright field TEM micrographs of PLMA brush-grafted silica NPs w...
Figure 11.2 Photos of 1 wt% dispersions of HNP-SiO
2
-4.1k in PAO in the init...
Figure 11.3 Friction curves for PAO SpectraSyn
TM
4 (A), PAO containing 1 wt...
Figure 11.4 (a) Friction curves for PAO SpectraSyn
TM
4 (i), PAO with 1.0 wt...
Figure 11.5 (a) Friction curves for PAO containing 1.0 wt% B-PC8-NP1-7.8k (...
Scheme 11.3 Molecular structure of ionic liquid [P8888][DEHP] (denoted as I...
Figure 11.6 Friction curves for the PAO SpectraSyn
TM
4 mixed with (a) 2% IL...
Figure 11.7 SEM micrographs and EDS elemental mapping of Fe, P, O, and Si o...
Scheme 11.4 (a) Molecular structures of poly(alkyl methacrylate)s with vari...
Figure 11.8 Optical transmittance as a function of temperature for a 10 mg ...
Figure 11.9 (A) Schematic illustration of the home-made friction test setup...
Guide
Cover
Title Page
Copyright
Preface
Table of Contents
Begin Reading
Index
End User License Agreement
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Hairy Nanoparticles
From Synthesis to Applications
Edited by Zhiqun Lin and Yijiang Liu
Editors
Dr. Zhiqun LinDepartment of Chemical andbiomolecular EngineeringNational University of SingaporeSingapore 117585Singapore
Prof. Yijiang LiuXiangtan UniversityCollege of ChemistryXiJiaoYangGuTangYuhu District411105 XiangtanChina
Cover Image: © Westend61/Getty Images
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Preface
Hairy nanoparticles (NPs), also known as polymer-grafted NPs, represent an important class of hybrid NPs, composed of a layer of polymer shell tethered to an NP core. The past several decades have witnessed rapid advances in synthesis, self-assembly, and application of a rich variety of hairy NPs, including zero-dimensional (0D) plain, hollow and core–shell NPs, one-dimensional (1D) plain, hollow and core–shell nanorods and nanowires, and two-dimensional (2D) nanosheets. Owing to their intriguing characteristics enabled by judiciously tailoring dimensions, compositions, architectures, and surface chemistry, these hairy nanomaterials find applications in optics, optoelectronics, magnetic devices, catalysis, sensors, and biotechnology, among other areas. Despite the impressive developments noted above, a book centered on a comprehensive discussion of hairy NPs herein referred to as hairy nanocrystals of different shapes (e.g. sphere-, rod-, star-, sheet-, prism-, and dumbbell-like) regarding their synthesis, self-assembly, interfacial properties, functionalities, and applications is yet to be available.
This motivates us to edit this book that offers the current field of knowledge from synthesis to self-assembly, property, and application of hairy NPs. The synthesis method for hairy NPs represents the primary focus of this book, as manifested from Chapters 1 to 4. Chapter 1 extensively surveys recent advances in the synthesis of hairy NPs via surface-initiated controlled radical polymerization (CRP) and their characterization. The preparation of hairy NPs via bulk microphase separation and solution self-assembly of linear block copolymers are discussed in Chapter 2. It is crucial to precisely control the topology, architecture, composition, size, surface chemistry, and self-assembly of hairy NPs, as these characteristics in turn greatly affect their properties and applications. As such, unimolecular block copolymer micelles are employed as nanoreactors to direct the synthesis of monodisperse hairy NPs in Chapter 3. Chapter 4 features the synthesis and environmentally responsive behavior of silica (nano)particles with binary mixed homopolymer brushes and thermoresponsive polymer brushes.
Self-assembly renders a facile, scalable, and cost-effective route to NP ensembles with well-defined structures and functionalities and thus readily tailorable properties. Notably, hairy NPs stand out as the appealing building blocks for self-assembly due to the highly tunable functionality of grafted polymers. Chapter 5 describes the recent progress in the self-assembly of hairy NPs and their representative applications, highlighting the interactions that govern the assembly and methods that enable the construction of NP assemblies. In Chapter 6, interfacial behavior of hairy NPs, including interfacial assembly, interfacial entropy consideration, and interfacial jamming, as well as single-chain NPs, is examined.
It is notable that significant progress in the design, synthesis, and applications of hairy hollow NPs with different morphologies and diverse internal, shell, and hairy structures is detailed in Chapter 7. The self-assembly of binary mixed homopolymer brush-grafted silica NPs (BMNPs) is presented in Chapter 8, including computer simulations and various factors influencing the self-assembled morphology of BMNPs. Chapter 9 investigates the energy transfer and plasmonic coupling scenarios of hairy plasmonic NPs via expediently integrating plasmonic NPs with hairy ligands.
In addition to the applications discussed in Chapters 1–9, the utility of hairy NPs in catalysis and oil lubrication is also summarized in this book. Particularly, Chapter 10 assesses how polymer ligands impact the catalytic efficiency of hairy metal NPs. Chapter 11 outlines the implementation of oil-soluble polymer brush-grafted NPs, synthesized via surface-initiated reversible deactivation radical polymerization, as environmentally friendly lubricant additives for friction and wear reduction.
This book aims to be an introductory resource for scientists and engineers in the fields of chemistry, materials science and engineering, polymer science and engineering, nanobiotechnology, and biomedicine in both academia and industry.
Finally, we greatly appreciate all of the authors who contributed to this book. In the course of editing this book, we received great support from Wiley, and we would like to particularly acknowledge the assistance of Alice Qian and Katrina Maceda.
Yijiang Liu, Xiangtan University
Zhiqun Lin, National University of Singapore
1Synthesis of Hairy Nanoparticles
Zongyu Wang1, Jiajun Yan1,2, Michael R. Bockstaller1, and Krzysztof Matyjaszewski1
1Carnegie Mellon University, Department of Chemistry, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
2ShanghaiTech University, School of Physical Science and Technology, 393 Middle Huaxia Road, Shanghai 201210, China
1.1 Introduction to Grafting Chemistry
Recent progress in the field of macromolecular science affords economically feasible materials with mechanical robustness, light weight, and advanced optical, thermal, or electronic transport performance to impact fields, such as energy storage, transportation, electronics, and bioengineering. Hybrid materials that derive novel and enhanced properties from the synergisms between distinct organic and inorganic (or biological) constituents play a particularly important role. Research in this area is often inspired by “nature” that employs multifunctional hybrid materials (such as “mollusk shells”) in which novel properties arise due to the hierarchical arrangement of constituents. An important theme is the role of interfaces in mediating the interactions between the constituents. Surface functionalization via anchored polymer chains has become a ubiquitously applied method to tune the physiochemical properties of the surface, leading to significant improvements in interface chemistry and engineering [1–11]. Advances in surface-initiated polymerization have enabled the synthesis of brush (or “hairy”) nanoparticles, a novel class of hybrid material “building blocks” that can be assembled into functional material architectures or that can be applied as fillers to augment the performance of polymer materials. The incorporation of nanoparticles allows for enhancing the performance of the polymer host without sacrificing the superior processability features of the host matrix. The ability to construct polymeric materials with defined or desired thermal, optical, catalytic, electronic, and mechanical performance rendered the so-called polymer nanocomposites one of the most active fields in modern macromolecular chemistry and engineering. Applications of brush particles to realize stimuli-responsive polymer hybrids [2, 8, 12, 13], antifouling paints [5, 14–16], colloidal stabilizers [17], adhesives [18], catalytic systems [19], electronic devices [20], and biosensors [21] have been demonstrated. Moreover, hairy nanoparticles prepared via surface-initiated polymerization have found application for the functionalization of various novel substrates, including nanofibers, mesoporous constituents, nanotubes, graphene, living cells, and protein nanocomposites [22–25]. This contribution summarizes recent advances in the field of surface-initiated polymerization, in particular, based on reversible-deactivation polymerization methods, that have been fundamental to the advances in polymer hybrid materials [10, 26, 27].
1.2 Surface Functionalization of Nanoparticles
The preparation of hairy nanoparticles starts with the introduction of functional groups onto nanoparticle surfaces to enable the subsequent coupling of polymer chains (“grafting-onto” approach) or initiating groups for surface-initiated polymerization (“grafting-from” approach). The generation of strong bonding between the polymer chains and inorganic substrates surface relies on the precise and proper selection of desired anchoring groups.
1.2.1 Surface Modification by Chemical Treatment
A large number of anchoring reagents with distinct functionalities were explored to fulfill the surface modification of the respective desired substrates. Table 1.1 includes some general functional groups and their suitable surfaces. Examples of anchoring reagents and the applicable functional groups are summarized and listed below. One of the most commonly used reagents for surface functionalization is silane-based coupling agents, as many commercially available functional silanes, including trimethoxy(vinyl)silane, (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane, and (3-chloropropyl)triethoxysilane, are available at a low price from the industrial sources. The introduced amino moieties are subsequently converted to different functionalities, including atom transfer radical polymerization (ATRP) initiating sites. Many other functionalities can also be incorporated through hydrosilylation reactions. The silanol group on the surface can react with the functional groups. Silane-based coupling agents can consume up to three halide or alkoxy functional groups. Hence, the anchoring reagent with multiple functionalities can form a stronger covalent bond to the surface of nanoparticles. However, the multifunctional silane coupling agents tend to self-polymerize and form a multilayered microstructure [60]. The construction of the multilayered structure empowers the coupling agents with functional groups to enclose the surface, therefore making them widely applicable to a broad range of substrates.
Pyrocatechol, also known as catechol, and its derivatives have attracted great attention in the past years [34, 61]. Pyrocatechol, especially dopamine or polydopamine, was originally recognized to assemble stable adhesion to the surfaces of metal oxide substrates by forming a chelate attachment [62]. Nevertheless, the breakthrough of dopamine-like peptides in the byssus of mussels expanded the application of (poly)dopamine as a universal surface modifier. Generally, dopamine self-polymerizes into a multilayered polydopamine covering the substrate [34]. The formation of polydopamine affords a large variety of surface functional groups, such as amino, hydroxyl, aromatics, and conjugated carbonyl [61, 63, 64]. Besides dopamine, other natural and synthetic compounds based on phenol/catechol were employed as anchoring reagents, including catechol-bearing peptides and tannic acid [65, 66].
Table 1.1 Surface anchoring groups and applicable surfaces.
Source: Yan et al. [59], table 1 (p. 198)/Reproduced with permission from Elsevier.
Anchoring group
Surface
Examples
References
Trihalo/alkoxysilane
Silica, metal oxide, metal, etc.
[28
–
31]
Halo/alkoxydimethylsilane
Silica
[32
,
33]
Catechol
Metal, metal oxide, carbon, etc.
[34
–
37]
Amino
Metal, metal oxide, carboxylic acid-functionalized surface
[38]
Carboxylic acid
Metal, metal oxide, amino-functionalized surface
[39
–
42]
Activated acyl
Hydroxy/amino-functionalized surface, cellulose
[43
–
45]
Phosphonic acid/phosphates
Metal oxide
[46
,
47]
Radical
Metal, metal oxide, carbon
[48
–
50]
Thiol/disulfide
Metal
[51
–
56]
Allyl
Hydrogen-treated silicon
[32]
Phosphine oxide
Quantum dots
[57
,
58]
The application of aliphatic acids to the functionalization of metal or metal oxide surfaces has been well explored in the field of inorganic surface modification [67]. Later, aliphatic acids, or amines, were utilized to stabilize inorganic colloid nanocrystals in organic dispersion [68–70]. Either carboxyl or amino groups can generate coordinative interaction with the metal atoms on the surfaces [70–72]. Nevertheless, low-cost aliphatic acids or amines, including oleic acid, stearic acid, octylamine, or dodecylamine, initially served simply for compatibilization with no reactive functional groups incorporated. Recent research proved the introduction of ATRP initiating sites or even polymer chains with carboxylic acid or amino chain ends onto the nanofiller surfaces [38, 39]. A carboxylate-based anchor showed high efficiency to modify a large variety of inorganic substrates. The incorporation of ATRP initiating moieties allowed the application of these anchoring reagents for the synthesis of hybrid polymer nanocomposite [39, 73]. Besides aliphatic acids or amines, another alternative approach to modify the surface of the inorganic substrate is the deposition of aniline or pyrrole [74]. However, their control over the surface functionality as well as the anchoring efficiency is not as facile as silane or dopamine coupling agents [75]. The hydroxyl- or amino-modified surfaces can directly react with the coupling agents based on derivatives of carboxylic acids, including acyl halide or active esters [43, 44, 76]. Compared to carboxylic acids, as one alternative surface anchoring agent, functional phosphonates and phosphates were used to graft polymer chains onto/from salts and metal oxides as they can build strong bond with the surface of metal oxide substrates [46, 77, 78]. Phosphine oxides functionalized the surface of selective quantum dots, including cadmium selenide or zinc sulfide [57, 58]. Additionally, radical species generated through heat, light, or redox reaction from the surface or precursors introduced functional moieties and formed covalent carbon–carbon/metal bonds on the substrate surfaces. For instance, thermal initiators attached to the surface of carbon substrates upon heating [79]; aryl radicals were produced through the electrochemical reduction of diazonium compounds [48, 80, 81]; and radical coupling with alkenes yields photochemically active surfaces [82, 83]. Similar to the typical process of radical coupling, hydrosilylation can connect allyl-based anchoring reagents and pretreated silicon substrates through either a thermal/photoinduced radical path or an organometallic catalytic path [32]. Organosulfur compounds can form a stable linkage with a wide range of metals, including gold, silver, mercury, iron, or copper. In these systems, thiols and disulfides were efficiently anchored to the metal surface, providing proper coupling functionalities. For instance, thiols are commonly employed to tune the size of gold nanoparticles [84]. Disulfides were prone to split into thiolates upon chemisorption on metal surfaces [85, 86]. Initiating sites or polymer ligands were incorporated onto surfaces of gold via coordination with compounds containing mercapto groups or thiol-terminated polymer ligands [51–53]. The essence of the sulfur–metal interaction is still under investigation [86, 87].
1.2.2 Surface Modification by Plasma Treatment
Plasma is a moderately ionized vapor of free electrons, ions, and radicals. It can be defined as a quasi-neutral particle system in the form of a gaseous or fluid-like blend [88–91]. During plasma treatment, functional groups are immobilized onto the surfaces or free radicals are produced. The radicals can react with oxygen from the atmosphere and be used for subsequent coupling or grafting reactions [92]. Gases such as argon, helium, oxygen, nitrogen, ammonia, and carbon tetrafluoride are particularly widely applied. The anchored moieties can further be used to bind other molecules or polymers to the surface to afford the targeted properties. For example, oxygen plasma treatment induced oxygen-containing functionalities including hydroxyl groups, peroxide groups, and carboxyl groups. Carboxyl and hydroxyl groups may also be incorporated via carbon dioxide or CO-plasma treatment [93]. The carbon dioxide plasma treatment creates ketones, aldehydes, and esters [94]. Nitrogen, ammonia, and nitrogen/hydrogen plasmas produce primary, secondary, and tertiary amines, and amides, which can be used to initiate polymerization in the postirradiation grafting procedure [95]. The pulsed plasma treatment can entail the deposition of halogen-containing initiator films on the surface of the substrate (Scheme 1.1) [96–98].
Scheme 1.1 Surface-initiated polymerization from pulsed plasma deposited halogen-containing initiator layers.
1.2.3 Synthesis of Functionalized Nanoparticles Through Initiator-Containing Precursors
Instead of tethering the initiators onto the nanoparticle surfaces, a one-step process to prepare uniform 3 nm initiator-containing organo-silica hybrid nanoparticles was reported [99], which relied on the polycondensation of brominated organosilane precursors, 3-(triethoxysilyl)alkyl α-bromoisobutyrate (TES-ABMP). The utilization of an initiator-modified precursor enabled one to spare the surface modification steps prior to polymerization, hence avoiding the generation of additional silica layers from coupling reactions. In Scheme 1.2, “green Br” refers to the bromine initiating sites that are essential for synthesizing the hairy nanoparticles, and “x” indicates the number of –CH2− units, which are attributed to preparing the corresponding organosilane precursor. The hybrid nanoparticles can readily be polymer-tethered through surface-initiated atom transfer radical polymerization (SI-ATRP) without additional post-functionalization [6].
Scheme 1.2 Synthesis of oSiO2 nanoparticles.
Source: Han et al. [99], scheme 1 (p. 1219)/Reproduced with permission from the American Chemical Society.
1.3 Synthesis of Hairy Nanoparticles
In the past decades, numerous methodologies and techniques have been explored for polymer–inorganic hybrid material synthesis. Modification of inorganic substrates with tethered polymer ligands optimally integrates the properties of both ingredients [100]. Polymer ligands could be synthesized either by “grafting-from” or “grafting-onto” approaches [101–103]. The “grafting-onto” method exploits the benefits of coupling reactions between the surface functionalities and the complementary anchoring blocks or (chain ends) of polymer ligands to be attached to the substrate surfaces [104], which is experimentally straightforward. On the other hand, the “grafting-from” modification is often preferred as it enables higher grafting densities and polymer shell thicknesses. Both the “grafting-onto” and “grafting-from” approaches involve reactions at a solid surface. In an alternative approach, hairy nanoparticles were synthesized through a “polymer-first” approach, for instance, by applying block copolymers as a template [105]. This procedure was further advanced to prepare covalently bonded hairy nanoparticles with more complicated morphologies, including nano-capsules [106], molecular bottlebrushes [107–109], and star polymers [110], as polymeric templates to prepare precisely controlled polymer–inorganic nanocomposites.
1.3.1 Surface-Initiated Polymerization/The “Grafting-from” Approach
In the “grafting-from” method (Scheme 1.3), tethered polymer ligands grow directly from the modified surfaces, enabling higher grafting density, which is one of the most significant advantages of this approach. The grafting density (unit: chains nm−2) of hairy nanoparticles is defined as the average number of polymer chains per unit surface area (unit: nm2) and represents a crucial parameter for tuning both the chemical and physical properties of brush-like composites.
Scheme 1.3 The “grafting-from” approach.
1.3.1.1 SI-Free Radical Polymerization
Conventional (free) radical polymerization (FRP) is the most industrially utilized polymerization technique [111]. It has a long history of grafting polymer brushes from inorganic particles [112, 113]. To perform SI-FRP from nanoparticles, a radical-generating moiety needs to be immobilized. Radicals may be generated via conventional azo initiators [113, 114], photoinitiators [115, 116], or ionizing irradiations [117, 118]. Similar to FRP in solution, surface-generated radicals undergo radical addition to vinyl monomers and the reaction proceeds via a chain-growth mechanism. The multifunctional nature of the nanoparticle “macroinitiators” allows the growth of multiple chains simultaneously on a single nanoparticle.
FRP is one of the least expensive polymerization techniques while it is compatible with the widest variety of vinyl monomers. It is also tolerant to many impurities, such as protic solvents (e.g. water or alcohol), coordinating/chelating agents, and electrophiles, and various polymerization conditions, including bulk, solution, suspension, and (mini/micro)emulsion polymerization [119]. SI-FRP inherits all these features.
Despite such advantages, its intrinsic limitations render SI-FRP a nonideal choice in the preparation of hairy nanoparticles. Due to the high frequency of diffusion-controlled random termination reactions, broad molecular weight distribution is virtually guaranteed for FRP. It may not be a problem for homogeneous systems, but with several hundred growing chains on each nanoparticle, such random distribution leads to a large particle-to-particle difference, and hence a large batch-to-batch difference, as well as gelation due to radical termination between particle brushes.
1.3.1.2 SI-ATRP
In FRP it is challenging to simultaneously optimize each parameter of the targeted materials, particularly when the polymerization of the tethered chains is carried out from surfaces. The advances in surface-initiated controlled radical polymerization (SI-CRP), also known as surface-initiated reversible deactivation radical polymerization (SI-RDRP), allow precise control over chain length, composition, brush shell thickness, and eventually polymer architecture at the same time. They afford an approach to modify various substrates with polymeric shells of different thicknesses meanwhile maintaining the robustness and versatility of the living polymerization technique. The high tolerance of SI-CRP as a synthetic method toward a wide variety of functionalities and extensive applicability enabled it to be broadly applied for the fabrication of hairy nanoparticles.
Scheme 1.4 General scheme for SI-ATRP.
Because of the high accessibility of alkyl halide functional groups on the surface and its high tolerance toward various reaction environments, process requirements, and impurities, SI-ATRP amounts to a majority of all “grafting-from” approaches (Scheme 1.4). SI-ATRP as well as its derivative techniques have been recognized as the most common controlled radical polymerization (CRP) approach for growing polymer ligands from substrate surfaces [4, 6, 10, 120], substantially augmenting the toolkit of radical polymerization. SI-ATRP with well-preserved chain-end fidelity was employed for the preparation of precisely controlled, densely tethered polymer ligands from colloidal nanocrystals [120–122]. Based on the dynamic equilibrium between propagating radicals and dormant species, a typical ATRP procedure is tempered by a redox pair of transition metal complex catalysts, especially copper complexes (CuI/L, CuII/L), Figure 1.1[123–126]. A conventional ATRP process typically includes initiation, propagation, activation/deactivation, and termination steps, similar to SI-ATRP. However, the heterogeneous system presents some special characteristics.
Determined by the diverse morphology of nanoparticles and the degree of surface functionalization, the density of initiating sites could vary in a wide range, up to a couple thousand per particle, resulting in hairy nanoparticles with a very high grafting density. To achieve good control throughout the process, the overall rate of the polymerization should be well-tuned to maintain a sufficient diffusion rate of monomers to the chain-end radicals.
Additionally, when the overall number of initiating sites or deactivators is not high enough, then reversible deactivation becomes too slow, and extra sacrificial initiators [127] or deactivators [110] are added to the reaction to maintain a sufficiently fast reversible deactivation to enable a controlled process. Besides, based on the general gelation theory, for functionalized particles containing a thousand initiating sites on the surface, just about 0.1% of interparticle couplings could result in macroscopic gelation [128]. Reagents containing α-bromoisobutyrate functional groups are commonly used to introduce initiating sites on the surface of nanoparticles for SI-ATRP. Recent work reported the development of a tetherable ATRP initiator, 12-(α-bromoisobutyramido)dodecanoic acid (BiBADA), which contains a long aliphatic spacer between a carboxyl group and an α-bromoisobutyramido chain end. Due to its versatility, BiBADA was used as a universal anchor for the surface modification of metal oxide nanoparticles (Table 1.2, Figure 1.2).
Figure 1.1 Illustration of equilibrium of typical RDRP techniques.
For some applications, the residual catalysts from SI-ATRP should be separated from the ultimate product. In the past decades, numerous methodologies were exploited to afford a precisely controlled polymerization with only ppm levels of copper complex catalyst. Reducing agents were employed to restore the activator of copper complexes with high reactivity, such as Cu/Me6TREN or Cu/TPMA [129]. There are examples utilizing chemical reducing agents, including activator regenerated by electron transfer (ARGET) ATRP [130, 131], supplemental activator and reducing agent (SARA) ATRP [132, 133], and initiator for continuous activator regeneration (ICAR) ATRP [134]. Later, external stimuli [135], for instance, electrochemical method [136, 137], photo-irradiation [138, 139], and ultrasound agitation [140–143], were applied to produce the reducing environments (Figure 1.3). These methods not only enabled ppm levels of copper complex catalyst but also allowed for spatial and/or temporal control over the process. Besides the Cu complex, other transition metal compounds, including Fe [144–146], Ru [147, 148], or Ir [149], could also regulate an ATRP equilibrium. The latest advancement of metal-free ATRP solved the dilemma of transition metal impurities in the polymer product. However, it is still challenging to reach a level of high versatility as well as good control over the reaction that is similar to Cu complexes [150–152]. The ATRP process was lately programmed by applying a DNA synthesizer, further expanding the versatility of this technique and promoting its efficiency [153]. Due to its potential to pattern the substrates with polymer ligands, ATRP procedures with external stimuli have drawn considerable attention to systems involving macroscopic substrates [154–159].
Table 1.2 Summary of polymer-grafted metal oxide nanoparticles synthesized by SI-ATRP using BiBADA.a)
Source: Reproduced with permission of Yan et al. [39], Copyright 2017, American Chemical Society.
Entry
Particle
Size (nm)
Monomer
M
n
b)
M
w
/
M
n
b)
σ
(nm
−2
)
c)
D
h
(nm)
d)
Alkaline earth
1
MgO
20
MMA
1.32 × 10
5
1.60
0.08
1600 ± 200
Transition metal
2
TiO
2
15
MMA
7.24 × 10
4
1.25
0.03
403 ± 5
3
Co
3
O
4
10–30
MMA
1.03 × 10
5
1.83
0.14
4800 ± 100
4
e)
NiO
10–20
MMA
7.69 × 10
4
1.28
0.14
236 ± 3
5
ZnO
18
MMA
8.77 × 10
4
1.33
0.17
282 ± 1
6
Y
2
O
3
10
MMA
1.66 × 10
5
1.72
0.24
650 ± 10
7
ZrO
2
40
MMA
5.56 × 10
4
1.52
0.15
236 ± 1
8
e)
La
2
O
3
10–100
MMA
6.35 × 10
4
1.23
0.48
317 ± 2
9
CeO
2
10
MMA
6.88 × 10
4
1.27
0.13
244 ± 1
10
WO
3
60
MMA
2.36 × 10
5
1.98
0.28
762 ± 5
Post-transition
11
α
-Al
2
O
3
30
MMA
2.37 × 10
5
2.10
0.06
501 ± 4
12
α
-Al
2
O
3
30
BA
2.42 × 10
4
1.24
0.06
385 ± 1
13
In
2
O
3
20–70
MMA
1.40 × 10
5
1.49
0.20
377 ± 9
14
ITO
20–70
MMA
1.23 × 10
5
1.92
0.11
396 ± 3
15
e)
SnO
2
35–55
MMA
1.64 × 10
5
2.24
0.22
377 ± 1
Metalloid
16
Sb
2
O
3
80–200
MMA
3.66 × 10
5
1.93
0.14
870 ± 20
Metallate
17
f)
BTO
200
MMA
1.85 × 10
2.38
0.43
715 ± 4
a) Typical reaction conditions: [MOx-Br, assuming 1 Br nm−2]0/[M]0/[CuBr2]0/[Me6TREN]0 = 1/1000/0.2/0.5, 50 vol% anisole, 1.0 mm × 1 cm copper wire, room temperature.
b) Determined by SEC.
c) Determined by molar mass and inorganic contents.
d)Z-Averaged hydrodynamic size in THF determined by DLS.
e) Nanoparticles functionalized with BiBADA.
f) [BTO-Br, assuming 1 Br nm−2]0/[M]0 = 1/3000.
Figure 1.2 Top scheme: synthesis of BiBADA and surface functionalization of metal oxide nanoparticles with polymer ligands. Characterization of ZrO2-g-PMMA nanoparticles: (a) Intensity-weighted hydrodynamic size distributions of ZrO2-g-PMMA as an example. (b) Photograph of a uniform dispersion of ZrO2-g-PMMA in THF. (c) TEM images of ZrO2-g-PMMA.
Source: Yan et al. [39], Reproduced with permission of American Chemical Society.
Figure 1.3 External control for various ATRP techniques.
Source: Dmitriy Kazitsyn/Adobe Stock.
The emergence of ARGET ATRP not only enabled the dramatic reduction of the concentration of copper complex catalyst to a ppm level but also facilitated the polymerization reaction to be tolerant to limited amounts of air [130, 131]. ARGET ATRP can be recognized as a “green” approach, which consumes ppm amount of the catalyst incorporated with the proper reducing agents including tin(II) 2-ethylhexanoate (Sn(EH)2) [130], ascorbic acids [160], phenol [161], hydrazine and phenyl hydrazine [134], excess inexpensive ligands [162], amines, or nitrogen-containing monomers [163]. ARGET ATRP confirmed that SI-ATRP is readily applicable to large-scale manufacturing on macroscopic substrates [28, 157, 164], even under a certain level of oxygen exposure [165–169]. The repeated redox cycle between the transition metal complex and excess reducing agents consumed all oxygen in the reaction vessel [164]. Another important benefit of ARGET ATRP is that the transition metal complex triggered side reactions are significantly reduced [170]. This helps to further push an ATRP reaction to completion (full conversion) and synthesize copolymers with larger molar mass while preserving chain-end functionality [171, 172], which was confirmed by efficient chain extensions [173].
In ICAR ATRP, an addition of standard free radical initiators is employed to continuously regenerate the extremely low levels of Cu/L catalyst concentration (5–50 ppm). The use of initiators in the continuous activator regeneration procedure could be considered as a “reverse” ARGET ATRP. At this very low concentration of copper activator, in some applications, removing or recycling the transition metal catalyst residues is no longer necessary. The polymerization is promoted to high conversion with low concentrations of a source of organic free-radical initiators [134]. The polymerization rate in ICAR ATRP is determined by the rate of decomposition of the added initiator, while the rate of deactivation and the molecular weight distribution are governed by KATRP[174, 175].
Cu wire (Cu0) can act as a reducing agent and induce a CuII deactivator comproportionation to produce the CuI species [176]. Cu0 can also play the role of a supplemental activator, where it directly reacts with alkyl halides and generates a propagating radical, even though a majority of the activation of alkyl halides is triggered by the CuI activator. Hence, this procedure is known as SARA ATRP [177]. The use of other transition metals, such as metallic Zn, Mg, Fe, and Ag, was explored to lower the deactivator concentration in ATRP [177, 178].
The use of chemical reducing agents generated oxidized residues in the polymer product. Therefore, it is important to develop a procedure of reduction via nonchemical means. Electrochemical reductions provide various easily tunable parameters to tune polymerization rates by pursuing the preferred concentration of the redox-active transition metal complexes. For example, a desired percentage of the CuIIBr2/Me6TREN deactivator species can be electrochemically reduced to CuIBr/Me6TREN activators to initiate a controlled ATRP reaction. The employed potential determines the activator/deactivator ratio ([CuI/L]:[CuII/L]), thus the rate of polymerization [136]. Temporal control of the reaction has become particularly valuable in SI-ATRP, as it offers the possibility to “pause/restart” the polymerization to check and monitor the status of reactions [179]. This procedure also enables temporal control over the polymerization, simply by switching on/off the current. The molar mass of polymer chains formed in the eATRP process grew linearly with monomer conversion and a low dispersity was achieved. The concentration of catalytic complex as low as 50 ppm was sufficient to retain a controlled polymerization showing first-order kinetics and narrow molecular weight distribution. Cu can be electrodeposited on the electrode and stripped, affording efficient catalytic complex regeneration [180]. eATRP was also employed to synthesize gradient copolymer grafted hairy nanoparticles where the thickness of polymer shell was governed by tuning space/location of the supporting substrates from the electrode [158, 181].
Due to the simple set-up, insignificant usage of additives, and a possible choice of employing daylight, the PhotoATRP procedure attracted considerable attention [138, 156, 182–190]. PhotoATRP was expanded from copper to iron as the metal catalytic complex [146]. PhotoATRP was successfully performed with ppm amounts of copper catalysts [183, 184, 191]. PhotoATRP in either organic solvents or aqueous solutions was carried out. Precise and well-defined control over polymerization in PhotoATRP enabled efficient chain extension as well as the preparation of block copolymers. The polymerization can be paused and restarted simply by switching on/off the photo-irradiation source. The excited copper catalytic complexes (CuII/L) were reduced in the presence of electron donors [182]. PhotoATRP from inorganic substrates was later extended to SI-PhotoATRP facilitated by an organic photoredox catalytic complex, generating precisely controlled polymer hybrid nanocomposites without metal residues [33, 179, 192].
The metal-free ATRP was mediated by photo-irradiation with multiple organic photoredox catalysts, including phenothiazines, phenazines, and phenoxazines [150, 152, 193, 194]. The metal-free ATRP showed excellent versatility for a broad range of different methacrylate monomers. Successful chain extension and block copolymer synthesis were combined with other CRP procedures, resulting in synthetic and morphological versatility. Furthermore, phenothiazine derivatives were utilized as novel metal-free photoredox catalytic complexes for the PhotoATRP of polyacrylonitrile (PAN) with desired molar mass and narrow molecular weight distribution. The well-preserved halogen chain-end fidelity of the synthesized PAN was confirmed either by the 1H NMR spectrum or the successful chain extension reaction [151].
A robust mechanically controlled ATRP of methyl acrylate was performed in an ultrasound bath with a ppm level concentration of copper catalyst by means of ultrasonication as the external stimulus and piezoelectric nanoparticles BaTiO3 (barium titanate) as the mechanoelectrical transducing materials in DMSO solution, using a frequency of 40 kHz [141, 195]. It was recently demonstrated that zinc oxide nanoparticles (ZnO) are even more efficient than BaTiO3 as piezoelectric material and could be applied in c. 100 times lower amount than BaTiO3[140].
1.3.1.3 SI-RAFT
RAFT polymerization is another well-explored CRP technique. The dynamic exchange in a RAFT process is based on the reversible addition-fragmentation of initiating/propagating radicals to chain transfer agents (CTAs), including dithioester or trithiocarbonate, Figure 1.1[196, 197]. The most important characteristic of RAFT polymerization is that it is mainly based on the classic FRP setups with the added RAFT agents. Free radical initiating species are applied to form the propagating species and maintain the polymerization rate; meanwhile, the concentration of RAFT agents defines the targeted molecular weight. RAFT polymerization involves degenerative chain transfer, which assures all the polymer chains propagate at the same rate, leading to polymers with narrow molecular weight distribution [198]. Compared to ATRP, the RAFT process can be used to polymerize some less reactive or functional monomers [199]. In addition, the colored reactive RAFT chain ends are usually needed to be removed to purify the harmful residues from the polymer product [200]. Moreover, external stimuli were also employed in RAFT polymerizations, such as photoinduced electron/energy transfer (PET)-RAFT polymerization [186, 201]. Unlike the classic RAFT polymerization, the propagating species in PET-RAFT is formed by the PET-excited photoredox catalytic complex from the RAFT agent. Thus, as the process does not require any free radical initiators, it exhibited a superior oxygen tolerance and excellent temporal/spatial control performance [186]. Other external controls, including ultrasound agitation [202] and electrochemical method [203], were also thoroughly investigated for the RAFT polymerization. Occasionally, oxygen can act as an external trigger for RAFT polymerization [204].
SI-RAFT polymerizations were also exploited [205]. The first reported SI-RAFT reaction was accomplished via the mechanistic transformation of an SI-ATRP polymerization [206]. An alternative approach to carry out a RAFT reaction was to trigger the reaction from tethered azo initiators on the surface and control the polymerization through free RAFT agents in the dispersion [207]. Polymerizations were also performed by directly immobilizing CTAs on the surface with initiating species in the reaction mixture [51].
SI-RAFT polymerization could be performed either via surface-tethered free radical initiating sites or surface-functionalized RAFT CTA agents. Generally, there are three different ways to carry out SI-RAFT polymerization from the surfaces, based on how the CTA is immobilized, Figure 1.4. With free radical initiating sites immobilized on the surface and untethered CTAs in solution, SI-RAFT exhibited the same kinetic features as SI-FRP [207]. In other approaches, either the R-group [206, 208] or the Z-group [209, 210] of the CTA was attached to the surface, a process termed SI-RAFT polymerization as the initiation step occurs in the reaction solution [4]. In the R-group anchoring case, the anchored CTA is typically synthesized from an ATRP initiator or its derivatives [208, 211]. The broad range of various functional CTAs, for instance, 4-(4-cyanopentanoic acid) dithiobenzoate, affords an alternative option for immobilizing the CTA functionalities in a direct/indirect manner [212]
