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 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 Organic Catalysis for Polymerisation written by Andrew Dove and published by Royal Society of Chemistry. This book was released on 2018-11-15 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years polymerisation using organocatalysts has become an appealing alternative to more traditional metal-based catalysts. Conferring numerous advantages including low cost and ease of use, as well as the ability to precisely control the synthesis of advanced polymer structures, organocatalysts are increasingly used in polymer synthesis. Organic Catalysis for Polymerisation provides a holistic overview of the field, covering all process in the polymer synthesis pathway that are catalysed by organic catalysts. Sub-divided into two key sections for ease of use, the first focuses on recent developments in catalysis and the applications of catalysts to the full range of polymerisations that they have been utilised in; the second concerning monomers, arranges the field by monomer type and polymerisation mechanism. The book will therefore, provide a complimentary view of the field, providing both an overview of state-of-the-art catalyst development and also the best methodologies available to create specific polymer types. Edited by leading figures in the field and featuring contributions from researchers across the globe, this title will serve as an excellent reference for postgraduate students and researchers in both academia and industry interested in polymer chemistry, organic chemistry, catalysis and materials science.

Download or read book Practical Medicinal Chemistry with Macrocycles written by Eric Marsault and published by John Wiley & Sons. This book was released on 2017-09-12 with total page 617 pages. Available in PDF, EPUB and Kindle. Book excerpt: Including case studies of macrocyclic marketed drugs and macrocycles in drug development, this book helps medicinal chemists deal with the synthetic and conceptual challenges of macrocycles in drug discovery efforts. Provides needed background to build a program in macrocycle drug discovery –design criteria, macrocycle profiles, applications, and limitations Features chapters contributed from leading international figures involved in macrocyclic drug discovery efforts Covers design criteria, typical profile of current macrocycles, applications, and limitations

Download or read book Sequence Controlled Polymers written by Jean-François Lutz and published by John Wiley & Sons. This book was released on 2018-04-09 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edited by a leading authority in the field, the first book on this important and emerging topic provides an overview of the latest trends in sequence-controlled polymers. Following a brief introduction, the book goes on to discuss various synthetic approaches to sequence-controlled polymers, including template polymerization, genetic engineering and solid-phase chemistry. Moreover, monomer sequence regulation in classical polymerization techniques such as step-growth polymerization, living ionic polymerizations and controlled radical polymerizations are explained, before concluding with a look at the future for sequence-controlled polymers. With its unique coverage of this interdisciplinary field, the text will prove invaluable to polymer and environmental chemists, as well as biochemists and bioengineers.

Download or read book N Heterocyclic Carbenes written by Eman A. Ali and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As much of the concern is being placed on metal-free polymerization, carbenes are attracting researcher attention. Besides their impact on organic synthesis, they played an integral role in several types of polymerization. This unique class of organocatalyst revives the preparation of polymeric materials that possess functional groups at each carbon atom on the polymer chain, which was hardly reached by conventional methods. This chapter will concern with the contribution of N-heterocyclic carbenes (NHCs) in the preparation of functional polymers from diversified monomers. Also, will discuss the advantages of N-heterocyclic carbenes in some conventional polymerization such as ring-opening and step-growth polymerizations along with the direct zwitterionic polymerization.

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 Peptide Applications in Biomedicine Biotechnology and Bioengineering written by Sotirios Koutsopoulos and published by Woodhead Publishing. This book was released on 2017-11-16 with total page 655 pages. Available in PDF, EPUB and Kindle. Book excerpt: Peptide Applications in Biomedicine, Biotechnology and Bioengineering summarizes the current knowledge on peptide applications in biomedicine, biotechnology and bioengineering. After a general introduction to peptides, the book addresses the many applications of peptides in biomedicine and medical technology. Next, the text focuses on peptide applications in biotechnology and bioengineering and reviews of peptide applications in nanotechnology. This book is a valuable resource for biomaterial scientists, polymer scientists, bioengineers, mechanical engineers, synthetic chemists, medical doctors and biologists. Presents a self-contained work for the field of biomedical peptides Summarizes the current knowledge on peptides in biomedicine, biotechnology and bioengineering Covers current and potential applications of biomedical peptides

Download or read book Amino Acids Insights and Roles in Heterocyclic Chemistry written by Zerong Wang and published by CRC Press. This book was released on 2023-05-26 with total page 1675 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first-of-its-kind four-volume book series, Amino Acids: Insights and Roles in Heterocyclic Chemistry, provides readers with up-to-date information on alpha-amino acids, the potential challenges in working with alpha-amino acids, the protecting groups for the carboxyl, amino and side chain groups of the amino acids, and the most popular heterocyclic compounds that are originating from alpha-amino acids. These heterocyclic compounds include hydantoins, thiohydantoins (including 2-thiohydantoins, 4-thiohydantoins, 2,4-dithiohydantoins), 2,5-diketopiperazines, N-carboxyanhydrides, N-thiocarboxyanhydrides, sydnones, sydnonimines, azlactones, pseudoazlactones, and oxazolidin-5-ones. This is the first resource to comprehensively collect all the heterocycles that can be directly prepared from alpha-amino acids. In addition, almost all kinds of synthetic methods for a particular type of heterocycles from alpha-amino acids are included, along with the detailed mechanistic discussions and experimental procedures. Volume 1: Protecting Groups collects and discusses the 260 protecting groups relating to amino acids, which have been organized by carboxyl group, amino group, and side chain groups. The conditions to introduce these protecting groups as well as their deprotecting procedures have also been incorporated, along with the physical properties, solvent effects, and temperature effects on the solubility of amino acids. It presents the solubility of glycine and phenylalanine in a variety of solvent systems to show the impact on amino acid, where glycine generally represents the polar amino acid whereas phenylalanine represents the amino acid of non-polar side chain. In Volume 2: Hydantoins, Thiohydantoins, and 2,5-Diketopiperazines, the author has compiled the three IUPAC accepted nomenclature systems for heterocyclic compounds, which will be very useful for readers working in the heterocyclic chemistry field for giving the synthesized molecules their correct names. In addition, three groups of heterocyclic compounds, i.e., hydantoins, thiohydantoins (including 2-thiohydantoin, 4-thiohydantoin and 2,4-dithiohydantoin), and 2,5-diketopiperazines, have been organized with updated literature information. Particularly, all three groups of heterocyclic compounds have demonstrated many important biological activities, particularly anticancer and antibacterial activities. On the other hand, these three groups of heterocycles can be applied as substrates to make other chemical derivatives, particularly novel unnatural amino acids. All their reactivities have been compiled and updated. These will be very valuable for readers who have been working in this area or have interest in this area. Volume 3: N-Carboxyanhydrides, N-Thiocarboxyanhydrides, and Sydnones presents up-to-date detailed information on two types of heterocyclic compounds that are originated from alpha-amino acids: NCAs/NTAs and sydnones/sydnonimines. The volume also covers the more than 10 initiating systems for the NCA monomers to undergo the ring-opening polymerization, which are very useful for readers in order to make living polypeptides/polypeptoids. In addition, the method to characterize these prepared polypeptides/polypeptoids are included. Particularly, two modern mass spectrometric techniques (MALDI-TOF and ESI-TOF) have been explained with detailed examples, where the elucidation of molecular weight of protein based on the ESI-TOF spectra have been given with a practical example as well as the theory that is based on, a unique feature of the volume. Volume 4: Azlactones and Oxazolidin-5-ones discusses two types of simple heterocycles that can be prepared from alpha-amino acids, i.e., azlactones (also known as oxazolones, 4-unsaturated azlactones included) and oxazolidin-5-ones. These heterocyclic compounds behave differently in both biological and chemical properties, and their biological activities are presented in a well-organized manner in this volume. This unique 4-volume set thoroughly covers more than seven types of heterocyclic compounds that are originated from alpha-amino acids, providing carefully compiled updated information with detailed examples. The author has shared many thoughtful insights based on his strong background in physical organic chemistry. The volumes will be highly valuable for graduate students and senior students, as well as for professors and researchers working in the field of medicinal and pharmaceutical chemistry, organic chemistry, organic synthesis, heterocycles, and proteins and peptides.

Download or read book N Heterocyclic Carbenes in Organocatalysis written by Akkattu T. Biju and published by John Wiley & Sons. This book was released on 2019-01-07 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Summarizing the emerging field of N-heterocyclic carbenes used in organocatalysis, this is an excellent overview of the synthesis and applications of NHCs focusing on carbon-carbon and carbon-heteroatom bond formation. Alongside comprehensive coverage of the synthesis, characteristics and applications, this handbook and ready reference also includes chapters on NHCs for polymerization reactions and natural product synthesis.

Download or read book Nitroxide Mediated Polymerization written by Didier Gigmes and published by Royal Society of Chemistry. This book was released on 2015-12-08 with total page 513 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitroxide-mediated polymerization is an important branch of controlled radical polymerization, which has revolutionised the preparation of polymer architectures and compositions. This is the first book dedicated to the topic and covers the history and development of nitroxide-mediated polymerization, as well as current techniques of academic and industrial interest. Nitroxide-Mediated Polymerization gathers together and comprehensively discusses all aspects of nitroxide-mediated polymerization, from fundamental principles through to industrial applications. A specific focus will be dedicated to the principle of the technique, its kinetics aspects, the synthesis of the controlling agents, the range of polymerizable monomers, its potential for preparation of advanced organic and hybrid materials and its status at the industrial stage. The book details all stages of the field, with chapters detailing the history, recent developments and novel materials in this fast developing area. Edited and written by expert researchers working in the field and academia this book focuses on highlighting the kinetic aspects of nitroxide-mediated polymerization, providing insight into the kinetics that can sometimes be hard to follow in published papers. The book will be of interest to polymer chemists and materials scientists at graduate level and above.

Download or read book Carbene written by Satyen Saha and published by BoD – Books on Demand. This book was released on 2022-03-30 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbenes are important molecules in chemistry because of their photochemistry and high reactivity. They have many potential applications in medicinal and materials chemistry. This book provides a comprehensive introduction to carbenes and discusses their characteristics, structure, and synthesis procedures. It gives special emphasis to N-heterocyclic carbenes (NHCs) and their metal complexes.

Download or read book Principles of Polymer Chemistry written by A. Ravve and published by Springer Science & Business Media. This book was released on 2012-05-24 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt: This successful textbook undergoes a change of character in the third edition. Where earlier editions covered organic polymer chemistry, the third edition covers both physical and organic chemistry. Thus kinetics and thermodynamics of polymerization reactions are discussed. This edition is also distinct from all other polymer textbooks because of its coverage of such currently hot topics as photonic polymers, electricity conducting polymers, polymeric materials for immobilization of reagents and drug release, organic solar cells, organic light emitting diodes. This textbook contains review questions at the end of every chapter, references for further reading, and numerous examples of commercially important processes.

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 Anionic Polymerization written by Nikos Hadjichristidis and published by Springer. This book was released on 2015-09-01 with total page 1075 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Biointerface Engineering Prospects in Medical Diagnostics and Drug Delivery written by Pranjal Chandra and published by Springer Nature. This book was released on 2020-07-21 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides detailed information on the surface and surface chemistry of various biointerfaces for the understanding and development of biosensors, biocompatible devices, and drug delivery systems. It highlights the role of interfacial phenomena towards the behaviour of biomolecules on different surfaces and their significance in recent applications. The book also addresses various surface engineering techniques for the modification of biomaterials that are implemented for improving biocompatibility. It provides an updated scientific concept of various interactions of biological systems with surfaces/modified surfaces at the molecular and cellular level. The chapters include various in-vitro, in-vivo, ex-vivo models to illustrate various aspects of Biointerface Engineering. Finally, the book elucidates troubleshooting strategies and future prospects of Biointerface Engineering in Medical Diagnostics and Drug Delivery.

Download or read book Cooperative Catalysis written by René Peters and published by John Wiley & Sons. This book was released on 2015-01-30 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by experts in the field, this is a much-needed overview of the rapidly emerging field of cooperative catalysis. The authors focus on the design and development of novel high-performance catalysts for applications in organic synthesis (particularly asymmetric synthesis), covering a broad range of topics, from the latest progress in Lewis acid / Brønsted base catalysis to e.g. metal-assisted organo catalysis, cooperative metal/enzyme catalysis, and cooperative catalysis in polymerization reactions and on solid surfaces. The chapters are classified according to the type of cooperating activating groups, and describe in detail the different strategies of cooperative activation, highlighting their respective advantages and pitfalls. As a result, readers will learn about the different concepts of cooperative catalysis, their corresponding modes of operation and their applications, thus helping to find a solution to a specific synthetic catalysis problem.