Anionic Synthesis Of Functionalized Linear And Star Branched Polymers

Novel methods for the synthesis of chain-end and in-chain functionalized polymers, as well as star polymers, were developed using anionic polymerization techniques. A new mechanism for the reaction of polymeric organolithium compounds with thiiranes has been found. The reaction of poly(styryl)lithium and poly(butadienyl)lithium with propylene sulfide and ethylene sulfide was investigated in hydrocarbon solution for the preparation of thiol-functional polymers. It was found by MALDI-TOF mass spectral analysis of the reaction products that the reaction proceeded by attack of the anion on the methylene carbon atom of the thiirane ring followed by ring opening to form the thiol-functionalized polymer. The reaction of poly(styryl)lithium with trimethylene sulfide did not produce the corresponding thiol-functionalized polymer; the resulting methyl-terminated polymer was formed by attack of the anion on the sulfur atom followed by ring opening to form a primary carbanion. A new method for synthesis of alkoxysilyl-functionalized polymers was developed. Using a general functionalization methodology based on the hydrosilation of vinyltrimethoxysilane with [omega]-silyl hydride-functionalized polystyrene, alkoxysilyl-functionalized polystyrene was obtained in high yield (83 %). The main side product was vinylsilane-functionalized polymer. A small amount of dimer (approximately 2 %) was formed from the hydrosilation reaction of silyl hydride-functionalized polymer and vinylsilane-functionalized polymer. Star polymers with an average number of 6.8 arms were obtained by reacting poly(styryl)lithium with 6.6 equivalents of vinyldimethylchlorosilane in benzene at 30 °C. It was found that, in benzene at 30 °C, vinyldimethylchlorosilane is an efficient linking agent for the preparation of well-defined star-branched polymers. In contrast, the reaction of poly(styryl)lithium with 5 equivalents of vinyldimethylchlorosilane in THF at -78 °C produced vinylsilane-functionalized polymer in high yield (> 93 %). Poly(styryl)lithium was reacted with 2.5 equivalents of vinyldimethylethoxysilane; reaction occurred exclusively by the addition of the living anion to the vinyl group. In-chain, dihydroxyl-functionalized polystyrene was prepared by reaction of poly(styryl)lithium and 1,3-butadiene diepoxide. The hydroxyl functionalities were activated with potassium naphthalenide. Addition of ethylene oxide monomer yielded the corresponding heteroarm polystyrene/poly(ethylene oxide) stars. Two commercially available triepoxides, N,N-diglycidyl-4-glycidyloxyaniline and Tactix 742, were used to prepare the corresponding 3-armed stars in high yield.

The term ‘miktoarm polymers’ refers to asymmetric branched macromolecules, a relatively new entry to the macromolecular field. Recent advances in their synthesis and intriguing supramolecular chemistry in a desired medium has seen a fast expansion of their applications. The composition of miktoarm polymers can be tailored and even pre-defined to allow a desired combination of functions, meaning polymer chemists can have complete control of the overall architecture of these macromolecules. By carefully selecting the composition, they can create supramolecular structures with intriguing properties, particularly for applications in biology. Miktoarm Star Polymers features chapters from experts actively working in this field, and provides the reader with a unique introduction to the fundamental principles of this exciting macromolecular system. Topics covered include the design, synthesis, characterization, self-assembly and applications of miktoarm polymers. The book is an excellent overview and up to date guide to those working in research in polymer chemistry, materials science, and polymers for medical applications.

The field of CMA (complex macromolecular architecture) stands at the cutting edge of materials science, and has been a locus of intense research activity in recent years. This book gives an extensive description of the synthesis, characterization, and self-assembly of recently-developed advanced architectural materials with a number of potential applications. The architectural polymers, including bio-conjugated hybrid polymers with poly(amino acid)s and gluco-polymers, star-branched and dendrimer-like hyperbranched polymers, cyclic polymers, dendrigraft polymers, rod-coil and helix-coil block copolymers, are introduced chapter by chapter in the book. In particular, the book also emphasizes the topic of synthetic breakthroughs by living/controlled polymerization since 2000. Furthermore, renowned authors contribute on special topics such as helical polyisocyanates, metallopolymers, stereospecific polymers, hydrogen-bonded supramolecular polymers, conjugated polymers, and polyrotaxanes, which have attracted considerable interest as novel polymer materials with potential future applications. In addition, recent advances in reactive blending achieved with well-defined end-functionalized polymers are discussed from an industrial point of view. Topics on polymer-based nanotechnologies, including self-assembled architectures and suprastructures, nano-structured materials and devices, nanofabrication, surface nanostructures, and their AFM imaging analysis of hetero-phased polymers are also included. Provides comprehensive coverage of recently developed advanced architectural materials Covers hot new areas such as: click chemistry; chain walking; polyhomologation; ADMET Edited by highly regarded scientists in the field Contains contributions from 26 leading experts from Europe, North America, and Asia Researchers in academia and industry specializing in polymer chemistry will find this book to be an ideal survey of the most recent advances in the area. The book is also suitable as supplementary reading for students enrolled in Polymer Synthetic Chemistry, Polymer Synthesis, Polymer Design, Advanced Polymer Chemistry, Soft Matter Science, and Materials Science courses. Color versions of selected figures can be found at www.wiley.com/go/hadjichristidis

This book presents these important facts: a) The mechanism of anionic polymerization, a more than 50-year challenge in polymer chemistry, has now become better understood; b) Precise synthesis of many polymers with novel architectures (triblock, multi-block, graft, exact graft, comb, cyclic, many armed stars with multi-components, dendrimer-like hyper-branched, and their structural mixed (co)polymers, etc.) have been advanced significantly; c) Based on such polymers, new morphological and self-organizing nano-objects and supra molecular assemblies have been created and widely studied and are considered nanodevices in the fields of nano science and technology; d) New high-tech and industrial applications for polymeric materials synthesized by anionic polymerization have been proposed. These remarkable developments have taken place in the last 15 years. Anionic polymerization continues to be the only truly living polymerization system (100 % termination free under appropriate conditions) and consequently the only one with unique capabilities in the synthesis of well-defined (i.e., precisely controlled molecular weight, nearly mono-disperse molecular weight distribution, structural and compositional homogeneity) complex macromolecular architectures. This book, with contributions from the world’s leading specialists, will be useful for all researchers, including students, working in universities, in research organizations, and in industry.

A variety of methods were used to make polymers with different architecture and functionalities. The linking chemistry of vinyldimethylchlorosilane (VDMCS) with poly(styryl)lithium (M[subscript n] = 1,700-3,000 g/mol) was studied. The average degree of branching varied from 7.5 to 9.4 with an increase in concentration of VDMCS (1.2 to 5.2 eq). The intrinsic viscosities and melt viscosities (at 160°C) of the star polymers were found to be less than half of that of the corresponding linear polystyrenes. [alpha]-Pyrrolidine-functionalized polystyrene (M[subscript n] = 2,700 g/mol, M[subscript w]/M[subscript n] = 1.03, 92.5%) was successfully synthesized from [alpha]-chloromethyldimethylsilane-functionalized polystyrene (M[subscript n] = 2,600 g/mol, M[subscript w]/M[subscript n] = 1.02) based on NMR spectroscopy, MALDI-TOF and ESI mass spectrometry. The stability of silyl hydride groups under atom transfer radical polymerization conditions was proven by copolymerizing methyl methacrylate and (4-vinylphenyl)dimethylsilane (VPDS). Tapered block copolymers of isoprene, VPDS, and styrene with narrow molecular weight distributions (1.04 and 1.05) were synthesized via anionic polymerization. Evidence regarding the topology of cyclic polybutadienes was obtained by Atomic Force Microscopy of grafted polymers obtained by grafting an excess of silyl hydride-functionalized polystyrene (M[subscript n] = 8,300 g/mol, M[subscript w]/M[subscript n] =1.01) onto cyclic polybutadiene (M[subscript n]=88,000 g/mol, M[subscript w]/M[subscript n] = 2.0). The reactivity of polyisobutylene carbocations was compared with respect to competitive electrophilic addition to a vinyl group versus silyl hydride transfer by investigating the reaction with VPDS. Based on GPC results, and 1H and 13C NMR spectroscopy, no evidence for any vinyl group addition was observed. A successful attempt was made to prepare electrospun fibers from fluoro-functionalized styrene-butadiene elastomers. The water contact angle of these surfaces was found to be 162.8° [plus or minus] 3.8° for the fibrous mat of the fluorinated polymers as compared to 151.2° [plus or minus] 2.4° for the analogous fibrous mat of the non-fluorinated polymers. In-chain functionalization of tapered styrene butadiene rubber using chloromethydimethylsilane was quantitatively done via a hydrosilation reaction. Pyrrolidine-functionalized styrene butadiene rubber was obtained in 71% yield after reacting pyrrolidine with chloromethyldimethylsilane-functionalized styrene butadiene rubber. In-chain, silyl hydride-functionalized, deuterated polystyrene (M[subscript n] = 2,100 g/mol, M[subscript w]/M[subscript n] = 1.01) was functionalized with allyl cyanide in the presence of Karstedt's catalyst to obtain in-chain cyano-functionalized, deuterated polystyrene (45% based on the mass of in-chain, cyano-functionalized deuterated polystyrene obtained).

After introductory chapters outlining principles and industrial applications, papers from a symposium of the August 1996 American Chemical Society meeting in Orlando, Florida are arranged in sections on fundamentals and processes, block copolymers, star polymers, diene polymers, other applications of controlled aniionic polymerization, and polymerization of polar and inorganic monomers. A sampling of topics: UV spectrophotometry as a practical tool for process monitoring, preparation of branched polystyrenes with known architecture, preparation of lithographic resist polymers by anionic polymerization. Annotation copyrighted by Book News, Inc., Portland, OR

Polymers are huge macromolecules composed of repeating structural units. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials. Due to the extraordinary range of properties accessible, polymers have come to play an essential and ubiquitous role in everyday life - from plastics and elastomers on the one hand to natural biopolymers such as DNA and proteins on the other hand. The study of polymer science begins with understanding the methods in which these materials are synthesized. Polymer synthesis is a complex procedure and can take place in a variety of ways. This book brings together the "Who is who" of polymer science to give the readers an overview of the large field of polymer synthesis. It is a one-stop reference and a must-have for all Chemists, Polymer Chemists, Chemists in Industry, and Materials Scientists.