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The Development Of Cationic Zinc Complexes As A New Class Of Lactide Polymerization Catalyst
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Book Synopsis The Development of Cationic Zinc Complexes as a New Class of Lactide Polymerization Catalyst by : Craig Andrew Wheaton
Download or read book The Development of Cationic Zinc Complexes as a New Class of Lactide Polymerization Catalyst written by Craig Andrew Wheaton and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Biometal Catalyzed Ring-opening Polymerization of Cyclic Esters by : Osit Karroonnirun
Download or read book Biometal Catalyzed Ring-opening Polymerization of Cyclic Esters written by Osit Karroonnirun and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Biodegradable polyesters represent a class of extremely useful polymeric materials for many applications. Among these polyesters, the biodegradable and biocompatible, polylactide is very promising for many applications in both medical and industrial areas. Other biodegradable polymers such as polytrimethylene carbonate, polybutyrolactone, polyvalerolactone, and polycaprolactone can be blended or copolymerized with polylactide to fine tune the properties to fit the needs for their applications. The properties of these polymers and copolymers depend upon the tacticity of the polymers which can be directly controlled by the catalysts used for polymer production. Therefore, it has been of great interest to develop new selective catalytic systems for the ring-opening polymerization of lactide and other cyclic monomers. This dissertation focuses on developing new zinc and aluminum complexes and studying their selectivity and reactivity of these complexes for the ring-opening polymerization of lactide and other cyclic monomers, i.e. trimethylene carbonate, beta-butyrolactone, delta-valerolactone, and epsilon-caprolactone. Herein, aspects of the ring-opening polymerization of lactide and other cyclic monomers utilizing novel zinc and aluminum complexes will be discussed in detail. In the process for the ring-opening polymerization of lactide, chiral zinc half-salen complexes derived from natural amino acids have shown to be very active catalysts for producing polymers with high molecular weight and narrow polydispersities at ambient temperature. The chiral zinc complexes were found to catalyze rac-lactide to heterotactic polylactides with Pr values ranging from 0.68-0.89, depending on the catalyst and reaction temperature employed during the polymerization process. The reactivities of the various catalysts were greatly affected by substituents on the Schiff base ligands, with sterically bulky substituents being rate-enhancing. Furthermore, a series of both chiral and achiral aluminium half-salen complexes have been synthesized and characterized. These aluminum complexes all showed moderate selectivity to the ring-opening polymerization of rac-lactide to produce isotactic polylactide with Pm value up to 0.82 in toluene at 70 degrees C. Moreover, some of the studied aluminum complexes displayed epimerization of rac-lactide to meso-lactide during the polymerization process. Kinetic studies for the ring-opening polymerization of lactide utilizing these zinc and aluminum complexes are included in this dissertation. Along with these studies, the copolymerization of lactide with epsilon-caprolactone and delta-valerolactone will also be presented.
Book Synopsis Studies Towards Degradable Polymers by : Peter Malatji
Download or read book Studies Towards Degradable Polymers written by Peter Malatji and published by . This book was released on 2012 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis New High-activity Zinc(II)-based Catalysts for Ring-opening Polymerization by : Ming Cheng
Download or read book New High-activity Zinc(II)-based Catalysts for Ring-opening Polymerization written by Ming Cheng and published by . This book was released on 2000 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Cationic Ring-Opening Polymerization by : Stanislaw Penczek
Download or read book Cationic Ring-Opening Polymerization written by Stanislaw Penczek and published by Springer. This book was released on 2014-03-12 with total page 317 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Phosphinimine Zinc Complexes and Neutral Phosphinimines for Ring Opening Polymerization of Lactides by : Rajesh Thapa
Download or read book Phosphinimine Zinc Complexes and Neutral Phosphinimines for Ring Opening Polymerization of Lactides written by Rajesh Thapa and published by . This book was released on 2015 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: Achiral arenesulfonates ligands having a (NNN) or (NNO) side arm have been developed (Chapter 2) and their respective zinc ethyl complexes, NNNZnEt 3.2 and NNOZnEt 3.3, have been synthesized and characterized using spectroscopic methods (Chapter 3). NNNZnEt as well as NNOZnEt complexes are stable under nitrogen atmosphere. In the NNOZnEt 3.3 complex the protons associated with the pendant (dimethylamino)ethyl arm are broad indicating that a fluxional process is operative, most likely dissociation of the (dimethylamino)ethyl arm at 25 °C in CD2Cl2. The fluxional behavior present in the 1H NMR spectrum of 3.2 could be arrested by cooling the CD2Cl2 solution to -60 °C. In Chapter 3, the reactivity of 3.2 and 3.3 with alcohols was explored in detail. NNOZnEt was found to be unstable in the presence of alcohols. The NNNZnEt complex does not show any reactivity with weak acids (pKa = 16), such as ethanol, anthrylmethanol or anthrylethanol. Strong acids (pKa = 8-10) like phenols protonate the zinc ethyl bond to produce zinc phenoxide complexes with release of ethane. The rate of the reaction is directly proportional to the acid strength (pKa) of the alcohols. The NNNZnEt complex as well as its corresponding phenoxides show dynamic behavior at 25 °C. The dimethylaminoethyl arms in these complexes are hemilable as indicated by 1H, 13C, 31P and variable temperature NMR, i.e., the dynamic behavior of these complexes was demonstrated. The detail structure of the NNNZnEt was elucidated by examining the single X-crystal structure of analogous air stable NNNZnMe complex. Zinc phenoxides 3.10-3.12 were isolated in good yield by reaction of NNNZnEt complex and one equivalent of the corresponding solid phenols in CH2Cl2 under N2. Zinc phenoxides 3.10- 3.12 were characterized by 1H, 13C, and 31P and multi-dimensional NMR. Fluxional behavior was observed at 25 °C for the pendant (dimethylamino)ethyl arm in complexes 3.10-3.12 as also seen in zinc alkyl complexes 3.7 and 3.13. The dynamic behavior due to association and disassociation of the (dimethylamino) ethyl arm in complexes 3.10- 3.12 could be halted by cooling the CD2Cl2 solutions to -40 °C. Complexes 3.10-3.12 were stable in dry CD2Cl2 for several days at 25 °C and 12 hours at 45 °C. The catalytic activity of zinc phenols with lactide were tested on NMR scale reactions. The discrete zinc phenoxide as well as in situ generated zinc phenoxides 3.10-3.12 show low catalytic activity with dl-lactide. The low reactivity of zinc phenoxides with dl-lactide is probably due to the low electrophilicity of the zinc center. In the second part of this dissertation (Chapter 4), a series of tolyl/phenylethyl phosphinimines 4.1-4.8 were synthesized by Staudinger reaction between azide and various phosphines. These phosphinimines were characterized using 1H, 13C, 31P NMR. In general, the phosphininimine only ring substituted with an electron donating group, such as methoxy or dimethylanino, enhances the basicity of the phosphinimines. The correlation between the basicity of the phosphinimines and the downfield shift of the alcohol hydroxyl group when activated by phosphinimine was studied. The catalytic activity of these phosphinimines towards ring opening polymerization of lactide is correlated by alcohol hydroxyl proton shift when interacted with an alcohol (1:1) in nonhydrogen bonding solvent CDCl3 at 25 °C under N2 atmosphere. The phosphinimines 4.5 to 4.14 were tested for ROP of lactides and their correlation with the basicity estimated with alcohol activation was shown. These phosphinimines represent highly active catalysts for ROP under N2 at ambient temperature. The phosphinimine 4.7 reacts with lactide monomer even in absence of alcohol initiation with reasonable reaction rate. Phosphinimines initiate the ROP of lactide even in the absence of initiating alcohol. However, the addition of alcohol enhances the rate of the reaction. We anticipate that the ease of handling of these catalysts, combined with their high reactivity on the ROP of lactide will make them useful to the synthetic community.
Book Synopsis Synthesis and Structures of Tridentate Ketoiminate Zinc Complexes Bearing Trifluoromethyl Substituents that Act as L-lactide Ring Opening Polymerization Catalysts by : Nomaan M. Rezayee
Download or read book Synthesis and Structures of Tridentate Ketoiminate Zinc Complexes Bearing Trifluoromethyl Substituents that Act as L-lactide Ring Opening Polymerization Catalysts written by Nomaan M. Rezayee and published by . This book was released on 2012 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Biopolyesters written by Wolfgang Babel and published by Springer. This book was released on 2003-07-01 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: Living systems synthesize seven different classes of polymers. They provide structure and form for cells and organisms, function as catalysts and energy storage and carry the genetic information. All these polymers possess technically interesting properties. Some of these biopolymers are already used commercially. This special volume of Advances in Biochemical Engineering/Biotechnology comprises 10 chapters. It gives an overview of the water insoluble biopolyesters, in particular of the microbially synthesized poly-hydroxyalkanoate (PHA) family. It reports the state of the art of metabolism, regulation and genetic background, the latest advances made in genetic optimization of bacteria, "construction" of transgenic plants and in vitro synthesis by means of purified enzymes. Furthermore, it describes relevant technologies and evaluates perspectives concerning increasing the economic viability and competitiveness of PHA and discusses applications in medicine, packaging, food and other fields.
Book Synopsis Cationic Organomagnesium Complexes as Homogeneous Catalysts for the Ring-opening Polymerization of Lactones by : Benjamin John Ireland
Download or read book Cationic Organomagnesium Complexes as Homogeneous Catalysts for the Ring-opening Polymerization of Lactones written by Benjamin John Ireland and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Polylactones are biodegradable polymers which may be used as alternatives to conventional plastics and have shown promise in novel medical applications. Industrial production of polylactones requires the use of a catalyst. The work described herein is directed toward the development of novel cationic magnesium-based lactone-polymerization catalysts. These cationic species are produced by alkide abstraction from a neutral precursor; a strategy which has seen only preliminary exploration in the context of lactone polymerization. The target catalyst system features a neutral phosphinimine-derivative ligand structure which was developed and produced specifically for the purpose of lactone polymerization catalysis. Target complexes were obtained by reaction of neutral alkylmagnesium precursors with protonated ligand derivatives. Syntheses and characterization of novel species are described herein. These catalysts are very active in the polymerization of 6-caprolactone, generating high molecular weight polymers in mere minutes under mild conditions. A preliminary study of polymerization catalysis is also reported.
Book Synopsis Synthesis, Characterization and Catalytic Activity Study of Zinc Aminobis(phenolate) Complexes Towards Ring-opening Polymerization of Rac-lactide by : Yi Liu
Download or read book Synthesis, Characterization and Catalytic Activity Study of Zinc Aminobis(phenolate) Complexes Towards Ring-opening Polymerization of Rac-lactide written by Yi Liu and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of bimetallic and trimetallic zinc complexes of amino-bis(phenolato) ligands was synthesized and characterized. Bimetallic complexes (ZnEt)2[L1] (1a) and (ZnEt)2[L2] (1b) (where [L1] = n-propylamine-N,N-bis(2-methylene-4,6-di-t-butylphenolate) and [L2] = n-propylamine-N,N-bis(2-methylene-6-t-butyl-4-methylphenolate) were prepared via reaction of the proligands H2[L1] and H2[L2] with ZnEt2 in pentane. A THF adduct (ZnEt)2[L1]·THF (1a·THF) was obtained by using THF as solvent. Treatment of 1a with one or two equiv. of isopropyl alcohol gave a trimetallic zinc complex Zn3(i-PrO)2[L1]2 (2). The catalytic activities of these complexes towards ring-opening polymerization (ROP) of rac-lactide were studied in the absence and presence of benzyl alcohol or isopropyl alcohol. These complexes exhibit moderate to good activity for ROP of rac-lactide both in the melt phase and solution. The influence of catalyst and co-initiator loading were studied and thermodynamic activation parameters were determined. Characterization of the polymers by GPC and MALDI-TOF MS showed controlled and living polymerizations for rac-lactide in the presence of alcohol.
Book Synopsis Solid State Polymerization by : Constantine D. Papaspyrides
Download or read book Solid State Polymerization written by Constantine D. Papaspyrides and published by John Wiley & Sons. This book was released on 2009-04-27 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most current guide to solid state polymerization Solid State Polymerization (SSP)is an indispensable tool in the design, manufacture, and study of polymers, plastics, and fibers. SSP presents significant advantages over other polymerization techniques due to low operating temperatures, inexpensive equipment, and simple and environmentally sound procedures. Combining fundamentals of polymer science, chemistry, physical chemistry, and engineering, SSP also offers many research applications for a wide range of students and investigators. Gathering and filtering the latest literature on SSP, Solid Solid State Polymerization offers a unique, one-stop resource on this important process. With chapters contributed by leaders in the field, this text summarizes SSP, and provides essential coverage that includes: An introduction to SSP, with chemical and physical steps, apparatus, advantages, and parameters SSP physical chemistry and mechanisms Kinetic aspects of polyesters and polyamides SSP Catalysis in SSP processes Application of SSP under high pressure conditions in the laboratory Engineering aspects regarding process modeling and industrial application Recent developments and future possibilities Solid State Polymerization provides the most up-to-date coverage of this constantly developing field to academic and industry professionals, as well as graduate and postgraduate-level students in chemical engineering, materials science and engineering, polymer chemistry, polymer processing and polymer engineering.
Book Synopsis Beyond Metallocenes by : Abhimanyu O. Patil
Download or read book Beyond Metallocenes written by Abhimanyu O. Patil and published by . This book was released on 2003 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: The past 15 years have witnessed tremendous advances in the design and use of organometallic complexes as precatalysts for olefin polymerization. Most recently, an intense search has been started in next-generation single-site catalysts. New approaches have been taken to ligand design. This research has yielded extraordinary results such as catalysts with activities as high or higher than those of conventional metallocenes, stereospecific and living polymerizations, and amazing new polymer structures such as highly-branched ethylene homopolymers. This volume presents some of the recent disclosures in this exciting and rapidly expanding field, featuring papers by some of the leading investigators.
Book Synopsis Guanidines as Reagents and Catalysts II by : Philipp Selig
Download or read book Guanidines as Reagents and Catalysts II written by Philipp Selig and published by Springer. This book was released on 2017-04-12 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Heterocyclic Chemistry presents critical reviews on present and future trends in the research of heterocyclic compounds. Overall the scope is to cover topics dealing with all areas within heterocyclic chemistry, both experimental and theoretical, of interest to the general heterocyclic chemistry community. The series consists of topic related volumes edited by renowned editors with contributions of experts in the field. All chapters from Topics in Heterocyclic Chemistry are published Online First with an individual DOI. In references, Topics in Heterocyclic Chemistry is abbreviated as Top Heterocycl Chem and cited as a journal
Book Synopsis Metalorganic Catalysts for Synthesis and Polymerization by : Walter Kaminsky
Download or read book Metalorganic Catalysts for Synthesis and Polymerization written by Walter Kaminsky and published by Springer. This book was released on 1999-06 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: 45 years after the discovery of transition metals and organometallics as cocatalysts for the polymerization of olefins and for organic synthesis, these compounds have not lost their fascination. The birthday of Karl Ziegler, the great pioneer in this metalorganic catalysis, is now 100 years ago. Polyolefins and polydienes produced by Ziegler-Natta catalysis are the most important plastics and elastomers. New impulses for the polymerization of olefins have been brought about by highly active metallocenes and other single site catalysts. Just by changing the ligands of the organometallic compounds, the structure of the polymers produced can be tailored in a wide manner. In invited lectures and posters, relevant aspects of the metalorganic catalysts for synthesis and polymerization are discussed in this book. This includes mechanism and kinetics, stereochemistry, material properties, and industrial applications.
Book Synopsis Late Transition Metal Polymerization Catalysis by : Bernhard Rieger
Download or read book Late Transition Metal Polymerization Catalysis written by Bernhard Rieger and published by Wiley-VCH. This book was released on 2006-03-06 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: Even some fifty years after their discovery, transition metals have lost none of their fascination. The use of complex compounds in these elements has not only revolutionized synthesis in the laboratory, but has also led to them playing an important role in many industrial applications. Each year, millions of tons of plastics are produced around the world and, by varying the ligands in the catalytically active compounds, the properties of the resulting polymers can even be tailored for use. For this purpose, sandwich compounds from early transition metals have been common until now, but interest has focused increasingly on the late transition metals. In this book, the world's leading authors from research and industry discuss the latest developments in research into palladium, zinc, iron and nickel catalysis. In so doing, they systematically introduce readers to the basic principles and illustrate how these innovative catalysts can be effectively used for polymerizations. The result is an ideal reference work, invaluable for every organic chemist working in catalysis or polymer research.
Book Synopsis Development of Late Transition Metal Insertion Polymerization Catalysts by : Tobias Friedberger
Download or read book Development of Late Transition Metal Insertion Polymerization Catalysts written by Tobias Friedberger and published by . This book was released on 2015 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polyolefins are the number one commercially produced polymeric material by volume, and find ubiquitous uses as plastics, elastomers, and fibers. They are produced from gaseous olefins such as ethylene and propylene by the action of a transition metal catalyst. Despite tremendous academic and industrial efforts and successes in catalyst development over the past decades, the copolymerization of polar functionalized olefins with sufficiently high activities still remains a largely unsolved issue. Late transition metal catalysts were shown to be more suitable for this kind of polymerization reaction due to their generally lower oxophilic character. The main goal of this thesis was the development of novel late transition olefin polymerization catalysts based on ruthenium and palladium. Prior to this work, only few active olefin polymerization Ru-catalysts were reported. Several series of complexes based on ruthenium were synthesized, characterized and investigated for olefin polymerization. Ru(II)-complexes of the type RuCl2(N,N,N)L with facially coordinating nitrogen donor ligands (N,N,N = trispyridyl-, trispyrazoyl-, trisimidazoyl-methane derivatives) were found to be inactive towards ethylene polymerization. Employing bisanionic disulfonate phosphines as ligands gave Ru-complexes that produced linear, high-molecular weight polyethylene in the presence of an aluminum-alkyl based cocatalyst. Increasing the electrophilicity of the complex, by decreasing the donor strength of the ligand and using higher oxidation state Ru(IV)-complexes, the polymerization activity could be increased, and one of the highest activities for any Ru-based catalyst was observed. Polar additives such as acetone fully inhibited even the most electron-rich catalysts and copolymerization reactions yielded no polymer. In a different approach to solve the same problem, Pd-diimine complexes were modified with pendant olefin and boronate groups. Pd-diimine complexes can facilitate the copolymerization of ethylene with acrylates, and interactions of the pendant Lewis acid group with the functional, Lewis basic comonomer was anticipated to increase catalyst activity. However, no effect of a pendant pinacol boronate was observed on the incorporation ratio of methyl acrylate in room temperature copolymerizations. The ability of the pendant olefin to coordinate to cationic Pd-species resulted in hemilabile effects. Increased catalyst stability at the cost of decreased activities was found in comparison with unfunctionalized ligands.
Book Synopsis Poly(lactic acid) Science and Technology by : Alfonso Jiménez
Download or read book Poly(lactic acid) Science and Technology written by Alfonso Jiménez and published by Royal Society of Chemistry. This book was released on 2015 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive overview of the synthesis, characterisation, properties and applications of poly(lactic acid) science and technology covering scientific, ecological, social and economic issues.
