Post-Polymerization Modification of Block Copolymers for Functionalization-Induced Self-Assembly
Post-Polymerization Modification of Block Copolymers for Functionalization-Induced Self-Assembly

Author: David H. Howe

Publisher:

Published: 2020

Total Pages: 127

ISBN-13:

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This thesis is focused on expanding the utility of post-polymerization modification (PPM) and establishing it as a viable route for the synthesis of self-assembled polymeric nanoparticles through three primary research projects. The first project demonstrates Pd-catalyzed, Suzuki-Miyaura cross-coupling (SMC) as a new, versatile method for PPM on well-defined polymers derived from RAFT polymerization. The second project aims to employ SMC as the driving force behind a novel strategy for inducing dynamic self-assembly of block copolymers into nanoparticles through a technique termed "functionalization induced self-assembly" (FISA). The final project of this thesis improves upon the versatility and ease-of-use of FISA by extending it to the base-catalyzed thiol-epoxide "click" reaction as the primary PPM driving in situ self-assembly, thus achieving convenient polymer nanoparticle synthesis under ambient conditions and atmosphere. Keywords: click reaction, nanoparticle, polymer, RAFT, self-assembly, Suzuki

The Synthesis of Modular Block Copolymers
The Synthesis of Modular Block Copolymers

Author: Mary Nell Higley

Publisher:

Published: 2007

Total Pages:

ISBN-13:

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A novel methodology has been developed for the formation of block copolymers that combines ring-opening metathesis polymerization (ROMP) with functional chain-transfer agents (CTAs), functional chain-terminators (CTs) and self-assembly. Telechelic homopolymers of cyclooctene derivatives that are end-functionalized with hydrogen-bonding or metal-coordination sites are formed via the combination of ROMP with a corresponding functional CTA. These telechelic homopolymers are fashioned with a high control over molecular weight and without the need for post-polymerization procedures. The homopolymers undergo fast and efficient self-assembly with their complement homopolymer or small molecule analogues to form block copolymer architectures. The block copolymers have similar association constants to small molecule analogues described in the literature, regardless of size or the nature of the complementary unit or the polymer side-chain. The ROMP of side-chain functionalized norbornene polymers is coupled with functional CTs to produce block copolymer with main- and side-chain self-assembly sites. Combinations of these norbornene polymers with their complement polymer via self-assembly produce non-covalent AB type block copolymers fast and efficiently. ABA type block copolymers are realized by combining the difunctional homopolymer formed via the CTA pathway with the CT synthesized mono-functional polymer. These polymers show similar association constants regardless of the sequence of polymer formation.

Synthesis and Applications of Copolymers
Synthesis and Applications of Copolymers

Author: Anbanandam Parthiban

Publisher: John Wiley & Sons

Published: 2014-06-23

Total Pages: 408

ISBN-13: 1118860489

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Understanding the reactivity of monomers is crucial in creating copolymers and determining the outcome of copolymerization. Covering the fundamental aspects of polymerization, Synthesis and Applications of Copolymers explores the reactivity of monomers and reaction conditions that ensure that the newly formed polymeric materials exhibit desired properties. Referencing a wide-range of disciplines, the book provides researchers, students, and scientists with the preparation of a diverse variety of copolymers and their recent developments, with a particular focus on copolymerization, crystallization, and techniques like nanoimprinting and micropatterning.

The Synthesis and Self-assembly of MPC Block Copolymers
The Synthesis and Self-assembly of MPC Block Copolymers

Author: Lauren Cowie

Publisher:

Published: 2013

Total Pages:

ISBN-13:

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Biocompatible and biodegradable poly(lactide)-2-methacryloyloxyethyl phosphorylcholine (PLA-PMPC) amphiphilic block copolymers were synthesized by a combination of Ring Opening Polymerization (ROP) and Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization techniques. The PLA-macroRAFT agent was synthesized by the derivatization of PLA-OH with RAFT agent 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPADB) achieving high levels of functionalization and narrow weight distributions (PDI range of 1.02-1.17). PLA-PMPC with varied MPC block lengths were synthesized yielding polymers with a narrow polydispersity PDI = 1.16-1.21. Triblock copolymers PMPC-PLA-PMPC with varying hydrophilic weight ratios were synthesized following an analogous method, the polymerizations were shown to be controlled with PDI's of 1.24 and 1.36. PLA-PMPC block copolymers with varied compositions were self-assembled using several techniques to target different morphologies. Nanostructures were characterised by DLS and TEM. Block copolymers with a larger PLA block length were shown to generate smaller aggregates i.e. micelles. The morphologies observed for the various block copolymers were consistent amongst different preparative techniques. Vesicle structures were reproducible by the self-assembly of PMPC50-PLA51-PMPC50, however, by preparing nanoparticles by direct dissolution micelles formed. The block copolymers were shown to encapsulate a hydrophobic dye in aqueous media thereby demonstrating its potential drug delivery applications.

Block Copolymers
Block Copolymers

Author: Nikos Hadjichristidis

Publisher: John Wiley & Sons

Published: 2003-04-28

Total Pages: 445

ISBN-13: 0471461342

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Polymers may be classified as either homopolymers, consisting of one single repeating unit, or copolymers, consisting of two or more distinct repeating units. Block copolymers contain long contiguous blocks of two or more repeating units in the same polymer chain. Covering one of the hottest topics in polymer chemistry, Block Copolymers provides a coherent overview of the synthetic routes, physical properties, and applications of block copolymers. This pioneering text provides not only a guideline for developing synthetic strategies for creating block copolymers with defined characteristics, but also a key to the relationship between the physical properties of block copolymers and the structure and dynamics of materials. Covering features of the chemistry and physics of block copolymers that are not found in comparable texts, Block Copolymers illustrates the structure-activity relationship of block copolymers and offers suggestions for the design of specific applications. Divided into five sections-Block Copolymers includes chapters on: * Block Copolymers by Chemical Modification of Precursor Polymers * Nonlinear Block Copolymers * Adsorption of Block Copolymers at Solid-Liquid Interfaces * Theory of Block Copolymer Segregation * Phase Transformation Kinetics * Block Copolymer Morphology * Block Copolymer Dynamics Polymer chemists, physicists, chemical engineers, and materials scientists, as well as graduate students in polymer science, will find Block Copolymers to be an invaluable text.

Synthesis and Characterization of Ionically Bonded Diblock Copolymers
Synthesis and Characterization of Ionically Bonded Diblock Copolymers

Author: Lei Feng (Chemical engineer)

Publisher:

Published: 2013

Total Pages: 0

ISBN-13:

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Block copolymers consist of two or more incompatible polymer chains linked by covalent bonds. These block copolymer can separate into nanometer sized domains whose morphology depends upon the size of the block and interactions between them. The properties of block copolymers can be modified and potentially improved by introducing noncovalent interactions to replace covalent linkages between blocks to form supramolecular block copolymers. These kinds of materials combine the microphase separation inherent to block copolymers with the facile synthesis of supramolecular materials thereby affording new and unique materials. This dissertation focuses on synthesis and characterization of PS-b-PMA block copolymers with ion-pair junctions.Firstly, the chain-end sulfonated polystyrene ([omega]-sulfonated PS) was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization and postpolymerization modification. In the postpolymerization modification two methods were investigated: in the first one, the polymer was converted to a thiol-terminated polymer by aminolysis. Then a sulfonic acid end-group was produced then by oxidation of the thiol end-group with m-chloroperoxybenzoicacid (m-CPBA); in the second method, the RAFT-polymerized polymer was directly sulfonated by oxidation with m-CPBA. After purification by column chromatography, [omega]-sulfonated PS was obtained by both methods with greater than 95% end-group functionality as measured by titration. The sulfonic acid end-group could be neutralized with various ammonium or imidazolium counter ions through acid-base or ionic metathesis reactions. These polymers with ionic end-group can be used as model supramolecular building blocks.Secondly, ammonium end functionalized polymethylacrylate (PMA) was synthesized directly by RAFT polymerization using functional RAFT agent. Then chain-end sulfonated polystyrene and ammonium end functionalized polymethylacrylate (PMA) were used to synthesize A-B block copolymers by two different methods: the first method was by mixing two oppositely charged end group functionalized polymers; the second method was to ionically bond a RAFT agent to the chain end of an end sulfonated polymer to generate a supramolecular macro RAFT agent then an A-B block copolymer was prepared by RAFT polymerization using supramolecular macro-RAFT agent. The polymerization kinetics were investigated and the molecular weight and the chemical structure of the block copolymers were characterized by 1H-NMR and SEC. The results show that the ion-bonded supramolecular block copolymer, PS-PMA, have been successfully prepared with controlled molecular weight and narrow distribution.Thirdly, the morphology of the ion-bonded supramolecular PS-PMA diblock copolymers were investigated by small-angle X-ray scattering (SAXS) and rheological techniques. Several covalently bonded PS-PMA block copolymers were synthesized by RAFT polymerization and their micro domain structures and rheology behaviors were also investigated. The results showed that the electrostatic interactions between the end ion groups are able to overcome the thermodynamic repulsion of two blocks result in the formation of diblock copolymers with similar behaviors and morphology of traditional covalent bonded diblock copolymers and their micro domain structures remain to high temperatures.

Post-polymerization Modification by Direct C-H Functionalization
Post-polymerization Modification by Direct C-H Functionalization

Author: Di Liu (Ph. D.)

Publisher:

Published: 2016

Total Pages: 258

ISBN-13:

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Post-polymerization modification of polymers is an important tool for accessing macromolecular materials with desired functional groups and tailored properties. Such strategy may become the only route to a target polymer when the availability or reactivity of the corresponding monomer is not suited for direct polymerization. Most post-polymerization modification processes are based on transforming functional groups that are pre-installed in the side chains or chain-ends of a polymer. Despite the excellent efficiency and versatility, they are limited to certain backbone structures and often require additional synthetic effort for the synthesis of the corresponding pre-functionalized monomers. More specifically, they are useful only when the pre-functionalized monomers can be readily prepared and incorporated to a polymer by direct polymerization. In contrast, direct functionalization of C-H bonds along the polymer backbone offers a markedly different strategy for the synthesis of functional polymers. Despite the inert nature, the ubiquity of the C-H bonds and their tunable reactivity make them ideal targets for selective chemical modification. In this dissertation, it is first demonstrated that poly(vinyl ester)s and poly(vinyl ether-co-vinyl ester) can be readily prepared via a ruthenium catalyzed C–H oxyfunctionalization of the corresponding poly(vinyl ether)s under mild conditions. The method can be further applied for the synthesis of high molecular weight poly(propenyl ester)s which cannot be obtained using other methods. In addition the method allows poly(isopropenyl ester) to be synthesized without the use of extremely high pressures. Using a similar strategy poly(ethylene glycol-co-glycolic acid) can be prepared by the ruthenium-catalyzed oxidation of poly(ethylene glycol) (PEG). A new process has been developed so that the transformation will cause little chain degradation. The presence of the hydrolytically labile ester groups in the PEG backbone renders the copolymer biodegradable, which may allow the PEG of higher molecular weight to be used in biomedical applications without the concerns of bioaccumulation of PEG into various organs. Lastly, it is demonstrated that azido-functionalized, isotactic polypropylene can be prepared via the direct C–H azidation of a commercially available polymer using a stable azidoiodinane. The azidated PP can further undergo copper-catalyzed azide-alkyne cycloaddition with alkyne terminated polymer to obtain PP-based graft copolymers. It is expected that the ability to incorporate versatile functional groups, such as azides, into common polyolefin feedstocks should expand their applications and potentially enable the realization of new classes of materials.

Synthesis of Original Block Copolymers by Combination of RAFT Polymerization and Supramolecular Self-assembly
Synthesis of Original Block Copolymers by Combination of RAFT Polymerization and Supramolecular Self-assembly

Author: Senbin Chen

Publisher:

Published: 2012

Total Pages: 0

ISBN-13:

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This work dealt with the preparation and the study of supramolecular block copolymers based on hydrogen-bonding between homocomplementary or heterocomplementary stickers. The synthetic strategy was based on the combination of RAFT-mediated controlled radical polymerization and supramolecular chemistry. In the Chapter 2, we developed a strategy relying on the design of RAFT agents bearing thymine/diaminopyridine (DAP) recognition pairs and capable to grow well-defined miktoarm star supramolecular copolymers. To further extend the scope of H-bonding RAFT agents, in the Chapter 3, we also investigated the preparation of RAFT agents functionalized with motifs exhibiting very high binding constants. The Hamilton/barbiturate couple (log(K)≈4-5) was selected to generate more stable supramolecular block copolymers. Aiming at elaborating original associating macromolecules and at simplifying the strategy of synthesis, we finally explored the preparation ABC triblock supramolecular copolymers based on PA11 oligomers (OPA11) in Chapter 4. Ligation of a relevant dithiobenzoate group on the oligomers afforded oligomeric RAFT agents that allow for the preparation of ABC triblock supramolecular copolymers, where A is semi-crystalline, B in rubbery state and C in glassy state. Studies on the incorporation of such copolymers in epoxy networks are under progress.