Post Polymerization Modification By Direct C H Functionalization

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Post-polymerization Modification by Direct C-H Functionalization

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.
Advances in Organic Synthesis

Author: Atta-ur-Rahman
language: en
Publisher: Bentham Science Publishers
Release Date: 2013-01-10
Advances in Organic Synthesis is a book series devoted to the latest advances in synthetic approaches towards challenging structures. It presents comprehensive articles written by eminent authorities on different synthetic approaches to selected target molecules and new methods developed to achieve specific synthetic transformations. Contributions are written by eminent scientists and each volume is edited by an authority in the field. Advances in Organic Synthesis is essential for all organic chemists in the academia and industry who wish to keep abreast of rapid and important developments in the field.
Functional Polymers by Post-Polymerization Modification

In modern polymer science a variety of polymerization methods for the direct synthesis of polymers bearing functional groups are known. However, there is still a large number of functional groups that may either completely prevent polymerization or lead to side reactions. Post-polymerization modification, also known as polymer-analogous modification, is an alternative approach to overcome these limitations. It is based on the polymerization of monomers with functional groups that are inert towards the polymerization conditions but allow a quantitative conversion in a subsequent reaction step yielding a broad range of other functional groups. Thus, diverse libraries of functional polymers with identical average degrees of polymerization but variable side chain functionality may easily be generated. Filling the gap for a book dealing with synthetic strategies and recent developments, this volume provides a comprehensive and up-to-date overview of the field of post-polymerization modification. As such, the international team of expert authors covers a wide range of topics, including new synthetic techniques utilizing different reactive groups for post-polymerization modifications with examples ranging from modification of biomimetic and biological polymers to modification of surfaces. With its guidelines this is an indispensable and interdisciplinary reference for scientists working in both academic and industrial polymer research.