Download or read book Zwitterionic Polymerization for the Synthesis of High Molecular Weight Cyclic Polymers written by Hayley A. Brown and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological isomerism in macromolecules represents a fascinating field of study. Linear polymers form the basis of much of the current scientific understanding of bulk polymer behavior due to their simple structure and synthetic accessibility. In contrast, cyclic polymers remain poorly understood due to the difficulty in generating sufficient quantities of pure samples; in particular, high molecular weight samples where phenomena related to entanglement could be observed have eluded polymer chemists until recently. Among the several strategies employed for the synthesis of high molecular weight cyclic polymers, recent reports have highlighted the utility of zwitterionic ring-opening polymerization (ZROP). Efforts to understand the N-heterocyclic carbene (NHC) mediated ring-opening of strained lactones have led to the development of several mechanistic models. Kinetic studies on the NHC-mediated polymerization of [epsilon]-caprolactone (CL) and [delta]-valerolactone (VL) were conducted to account for the notably high molecular weight cyclic polyerms generated. While the two monomer systems are closely related and polymerize with the same NHC initiators, a difference in the dependence of the reaction rate on monomer is observed. A general mechanism is proposed for the polymerization of VL. Exploiting the utility of ZROP to generate high molecular weight poly([epsilon]-caprolactone) allowed for a comparative study on the bulk crystallization of cyclic PCL and linear PCL across a range of molecular weights. WAXS and SAXS studies show that linear and cyclic PCL exhibit the same global and local crystalline structure but that cyclic PCL crystallizes more rapidly than linear PCL. Isothermal DSC crystallization kinetic studies support this observation and indicate that the difference in crystallization rate increases with increasing molecular weight. Approximating the equilibrium melting temperature of these samples using the Hoffmann-Weeks method indicates that there is no significant difference in Tm0 between cyclic and linear PCL. In an attempt to broaden the scope of initiators for the ZROP of strained lactones, the use of amidines for the polymerization of lactide was explored. 1,8-Diazabicyclo[5.4.0] undec-7-ene (DBU) and 1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) were shown to mediate the ZROP of lactide to give predominantly cyclic poly(lactide) (PLA). A notable solvent effect with no polymerization occurring in neat tetrahydrofuran (THF), fast polymerization with formation of significant amounts of linear PLA in dichloromethane (DCM), and moderate rate of polymerization with minimal formation of linear PLA in THF:DCM blends. DFT computations suggest that the formation of a neutral tricyclic species, a zwitterionic species, and a ketene-aminal are energetically feasible. This ketene-aminal is thought to be the source of the linear PLA observed. Our efforts to develop a more hydrolytically stable family of cyclic polymers led to the investigation of the ZROP of strained cyclic carbosiloxanes. NHC-mediated polymerization of 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane occurs rapidly to give polymers with molecular weights exceeding 106 g/mol. While these polymerizations are difficult to control, the cyclic topology of the resulting polymers could be confirmed by comparative dilute solution viscosity studies and MALDI-TOF MS. As a complimentary strategy to the use of neutral nucleophiles to initiate anionic-like zwitterionic polymerization, neutral Lewis acids were tested for the electrophilic zwitterionic ring opening polymerization (EZROP) of strained heterocycles. Polymerization of 2-ethyl-2-oxaline proceeds slowly at elevated temperature with boron-based Lewis acids to give HF-capped linear chains, determined by MALDI-TOF MS. In contrast, the polymerization of 3,3-dimethyloxetane proceeds very rapidly at room temperature with B(C6F5)3 to give a mixture of polymer products likely resulting from methyl scrambling between chains.
Download or read book N heterocyclic Carbene Mediated Zwitterionic Polymerization for Cyclic Polymers written by Eun Ji Shin and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Zwitterionic polymerization involves a propagating species with both positively and negatively charged groups. Previous investigations on zwitterionic polymerization concern alternating copolymerization of nucleophilic and electrophilic monomers and polymerization of isolated stable zwitterionic monomers. More recently, the ring-opening polymerization of cyclic monomers using nucleophilic initiators have been studied. Specifically, the zwitterionic polymerization of cyclic esters using N-heterocyclic carbenes (NHCs) is the focus of this thesis. The N-heterocyclic carbene mediated zwitterionic polymerization of cyclic monomers provides an expedient route to polymers of various architectures, such as cyclic polymers, cyclic gradient copolymers and linear telechelic polymers. The ring-opening polymerization of lactide initiated by NHCs generates cyclic poly(lactide)s of defined molecular weight and molecular weight distribution. Kinetic studies implicate a mechanism that involves a slow initiation step and a propagation step that is much faster than depropagation and chain termination by cyclization. Stochastic simulations and chain extension experiments showed that only a fraction of the NHC forms the active zwitterion in solution, leading to both chain extension of the zwitterions and re-initiation of the NHC upon addition of the second batch of monomer. These results prompted investigation of a more efficient way to prepare cyclic block copolymers. The difference in reactivity of NHCs towards different monomers was exploited to synthesize cyclic block copolymers of valerolactone (VL) and caprolactone (CL). The faster ring-opening of VL relative to CL resulted in a gradient cyclic copolymer comprised of VL-rich sequences that transition to CL-rich sequences in a cyclic macromolecule, instead of a cyclic diblock copolymer. This work not only provides a simple batch copolymerization protocol to produce cyclic gradient copolymers, but also demonstrates the marked difference in reactivity of the NHCs compared to metal catalysts, which produce random copolymers. Stereocomplexation behavior has been observed in blends of linear poly(L-lactide) and linear poly(D-lactide). The influence of topology on the formation of stereocomplex was investigated using blends of linear and cyclic poly(lactide)s prepared by NHC mediated zwitterionic polymerization. The linear/cyclic and cyclic/cyclic blends all form stereocomplexes when annealed. Analyses of data from various characterization techniques indicate that the cyclic topology imposes constraints on the stereocomplexation formation. The purity of the cyclic polymers is always a concern in the synthesis and physical property studies. Attempts to identify and quantify the linear contamination in cyclic poly(caprolactone) samples are described. Esterification reactions targeting the hydroxyl endgroups of linear contaminants were not successful, but the macroinitiator approach where the linear contaminant in a cyclic polymer sample is used as the macroinitiator to grow polymers to identify and remove the linear contamination shows promise. A cyclic polymer more robust to post-polymerization chemistry may be needed for more thorough purity studies.
Download or read book Cyclic Polymers written by J. A. Semlyen and published by Springer Science & Business Media. This book was released on 2000-08-31 with total page 804 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cyclic Polymers (Second Edition) reviews the many recent advances in this rapidly expanding subject since the publication of the first edition in 1986. The preparation, characterisation, properties and applications of a wide range of organic and inorganic cyclic oligomers and polymers are described in detail, together with many examples of catenanes and rotaxanes. The importance of large cyclics in biological chemistry and molecular biology is emphasised by a wide coverage of circular DNA, cyclic peptides and cyclic oligosaccharides and polysaccharides. Experimental techniques and theoretical aspects of cyclic polymers are included, as well as examples of their uses such as ring opening polymerisation reactions to give commercially important materials. This book covers a wide range of topics which should be of interest to many scientific research workers (for example, in polymer science, chemistry and molecular biology), as well as providing a reference text for undergraduate and graduate students.
Download or read book New Methods of Polymer Synthesis written by J.R. Ebdon and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: Few polymer chemists have much familiarity with recent developments in the synthesis of speciality polymers. This volume provides up-to-date reviews of areas of current interest and is directed at polymer chemists in the academic world and industry.
Download or read book Synthesis and Properties of Large Ring Macromolecules written by Wonhee Jeong and published by . This book was released on 2008 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis of Polymers written by Dieter A. Schlüter and published by John Wiley & Sons. This book was released on 2012-05-14 with total page 1229 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book New Methods Polymer Synthesis written by J. R. Ebdon and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most practitioners and students of polymer chemistry are familiar, in general terms at least, with the established methods of polymer synthesis - radical, anionic, cationic and coordination addition polymerization, and stepwise con densation and rearrangement polymerization. These methods are used to synthesize the majority of polymers used in the manufacture of commercially important plastics, fibres, resins and rubbers, and are covered in most introduc tory polymer chemistry textbooks and in most undergraduate and graduate courses on polymer science. Fewer polymer chemists, however, have much familiarity with more recent developments in methods of polymer synthesis, unless they have been specifically involved for some time in the synthesis of speciality polymers. These developments include not only refinements to established methods but also new mechanisms of polymerization, such as group transfer and metathesis polymerization and novel non-polymerization routes to speciality polymers involving, for example, the chemical modification of preformed polymers or the linking together of short terminally functionalized blocks.
Download or read book Polymer Synthesis Theory and Practice written by Dietrich Braun and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Laboratory Manual contains detailed descriptions for the synthesis and characterization of macromolecules. Around 110 elaborated examples, consisting of descriptions of experiments, as well as sufficient theoretical explanations enable the reader to learn about the syntheses, modification, characterization and properties of polymers including recent developments. All experiments can be conducted with adequate laboratory equipment. Suitable for students in organic and polymer chemistry as well as for chemists in industry who want to acquaint themselves with the theoretical and practical aspects of macromolecular chemistry.
Download or read book Polymer Synthesis Theory and Practice written by Dietrich Braun and published by Springer Science & Business Media. This book was released on 2006-10-14 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first English edition of this book was pubUshed in 1971 with the late Prof. Dr. Werner Kern as coauthor. In 1997, for the preparation of the third edition, Prof. Dr. Helmut Ritter joined the team of authors and in 2001 Prof. Dr. Brigitte Voit and Prof. Dr. Matthias Rehahn complemented this team. The change in authors has not altered the basic concept of this 4th edition: again we were not aimed at compiling a comprehensive collection of recipes. In stead, we attempted to reach a broader description of the general methods and techniques for the synthesis, modification, and characterization of macromo- cules, supplemented by 105 selected and detailed experiments and by sufficient theoretical treatment so that no additional textbook be needed in order to under stand the experiments. In addition to the preparative aspects we have also tried to give the reader an impression of the relation of chemical structure and mor phology of polymers to their properties, as well as of areas of their application.
Download or read book Conjugated Polymers written by Klaus Müllen and published by Royal Society of Chemistry. This book was released on 2013-10-18 with total page 503 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conjugated polymers are gaining a lot of interest due to their inherent functional properties and applications in plastic electronics. Their characteristic charge transporting and conducting properties produces features including coloration, photoluminescence, electroluminescence, photoconductivity, and electrochromism. In order to develop new functional polymers, researchers need the background information on the synthesis of the different polymer systems. Conjugated Polymers focuses on the practical preparation of conjugated polymers with each chapter discussing a particular type of conjugated polymer including a general explanation of the polymer, experimental details for synthesis and characterization. Edited by world leading experts in the field of conjugated polymer synthesis, the book serves as a convenient guide for advanced undergraduate level and above.
Download or read book Polymer Synthesis written by Stanley R. Sandler and published by Gulf Professional Publishing. This book was released on 1992 with total page 622 pages. Available in PDF, EPUB and Kindle. Book excerpt: This revised and updated second edition of Polymer Syntheses, Volume I brings together useful preparative methods for polymers and resins by functional group type that are of interest to both academic and industrial researchers. Several new directions for polymerization procedures have been included and are organized by various methodologies. Tables of physical property data and preparations make this book a valuable addition to any research library or research group. Provides detailed directions for the synthesis of various functional groups Includes up-to-date references to the journal literature and patents (foreign and domestic) Reviews the chemistry for each functional group and suggests where additional research is needed
Download or read book Synthesis of Novel Zwitterionic Polymers written by Matthew Skinner and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the synthesis, characterization, and investigation of novel zwitterionic polymers containing phosphorylcholine (PC), sulfobetaine (SB), and functional choline phosphate (CP) zwitterions for use as surfactants, self-assembled nanomaterials, and therapeutics. Facile, reproducible, and modular chemistries were utilized for incorporating zwitterions into a range of polymer backbones, and strategies were developed for overcoming difficult challenges encountered in zwitterionic polymer synthesis, especially related to the varying solubility of zwitterions, hydrophobic polymers, and functional comonomers. Synthetic strategies utilized in this work give access to well-defined materials with narrow molecular weight distributions, tunable compositions and architectures, and versatile chemical functionality. Chapter 2 describes the synthesis of water-soluble PC- and SB-functionalized siloxane polymers. PC- and SB-siloxane homopolymers and block copolymers were synthesized using thiol-ene 'click' chemistry, and their assembly in water and at oil-water interfaces was investigated. Chapter 3 describes the preparation of zwitterionic block copolymer analogues of commercial Pluronic® surfactants. PC-containing triblock copolymers were prepared with tunable zwitterion content (5-47 mole percent) and relatively narrow molecular weight distributions. These block copolymer amphiphiles readily formed nanoparticles in water and served as novel surfactants. Through the copolymerization of PC- and CP-methacrylate monomers, functional mimics of conventional Pluronic structures became amenable to crosslinking and the successful synthesis of nanomaterials and robust gels. Chapter 4 presents the in vivo evaluation of poly(2-methacryloyloxyethyl phosphorylcholine)-doxorubicin (polyMPC-Dox) prodrugs for treating human ovarian tumors (SKOV-3). In human ovarian tumor-bearing mice, polyMPC-Dox prodrugs with an approximate Dox loading of 19 weight percent accumulated in tumor tissue at twice the level of free Dox, and animals treated with polyMPC-Dox exhibited enhanced survival and retarded tumor growth compared to conventional Dox treatment. Finally, Chapter 5 augments the polyMPC prodrug concept with the development of polymer-temozolomide (TMZ) conjugates intended for glioblastoma treatment. PolyMPC-TMZ prodrugs were prepared by the controlled free radical copolymerization of MPC and novel TMZ-methacrylate monomers, affording copolymers with random and block architectures. Polymer conjugation significantly improved the solution stability of TMZ, and the antitumor activity of polyMPC-TMZ prodrugs was demonstrated in TMZ-sensitive (U87MG) and TMZ-resistant (T98G) glioblastoma cell lines. The impact of drug loading, polymer architecture, and adjuvant co-delivery on the cytotoxicity of polyMPC-TMZ conjugates was investigated.
Download or read book Principles of Polymer Design and Synthesis written by Wei-Fang Su and published by Springer Science & Business Media. This book was released on 2013-10-09 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: How can a scientist or engineer synthesize and utilize polymers to solve our daily problems? This introductory text, aimed at the advanced undergraduate or graduate student, provides future scientists and engineers with the fundamental knowledge of polymer design and synthesis to achieve specific properties required in everyday applications. In the first five chapters, this book discusses the properties and characterization of polymers, since designing a polymer initially requires us to understand the effects of chemical structure on physical and chemical characteristics. Six further chapters discuss the principles of polymerization reactions including step, radical chain, ionic chain, chain copolymerization, coordination and ring opening. Finally, material is also included on how commonly known polymers are synthesized in a laboratory and a factory. This book is suitable for a one semester course in polymer chemistry and does not demand prior knowledge of polymer science.
Download or read book Click Polymerization written by Anjun Qin and published by Royal Society of Chemistry. This book was released on 2018-08-28 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Click Polymerization has been edited by world renowned experts and provides an authoritative guide to this reaction type.
Download or read book New Methods for Polymer Synthesis written by W.J. Mijs and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 327 pages. Available in PDF, EPUB and Kindle. Book excerpt: The art and science of macromolecular architecture is based on synthesis, analysis, processing, and evaluation of physical properties of polymers. The growing specificity of available synthetic methods and the increasing refinement of analytical and physical analysis are gradually providing a deeper insight into structure-property relationships of polymers, upon which many applications can be based. This book deals with recent methods for polymer synthesis. Those that lead to specific structures have been selected especially. Background, mechanism scope and limitations, and illustrative procedures are given for each method. With this layout the editor hopes that the book will provide a practical guideline, for the synthetic polymer chemist in industry or at a university graduate school, on how to apply the methods in the design of new polymer structures. The editor is grateful to the authors not only for their contributions containing interesting new developments in polymer synthesis, but also for the way they have fitted their text into the general framework of the book. The elegant chemistry described in the following chapters will, it is hoped, inspire more organic chemists to apply their skills to polymer synthesis, where the beauty of organic chemistry in terms of structural control and reactivity may be even more apparent than in the low molecular field.
Download or read book Synthetic Methods in Step Growth Polymers written by Martin E. Rogers and published by John Wiley & Sons. This book was released on 2003-08-08 with total page 619 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alles über die Stufenwachstums-Polymerisation - von Syntheseverfahren und Reinigungsmethoden bis zur Charakterisierung der Produkte - finden Sie in diesem Buch. - bietet einen Ausblick auf zukünftige Trends - mit historischen Informationen - erläutert die Klassifikation von Stufenwachstumspolymeren
Download or read book Polymer Synthesis written by Guojian Wang and published by Walter de Gruyter GmbH & Co KG. This book was released on 2020-11-23 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book systematically presents fundamental principles, properties, implementation methodologies, technologies and applications of polymer synthesis. Ring opening metathesis polymerization, click chemistry, macromolecular self-assembly, carbon nanomaterials and their modification with polymers are discussed in detail. With abundant illustrations, it is an essential reference for polymer chemists, material scientists, and graduate students.
