Synthesis Characterization And Catalytic Activity Study Of Zinc Aminobisphenolate Complexes Towards Ring Opening Polymerization Of Rac Lactide

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Synthesis, Characterization and Catalytic Activity Study of Zinc Aminobis(phenolate) Complexes Towards Ring-opening Polymerization of Rac-lactide

Author : Yi Liu
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (132 download)

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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.

Phosphinimine Zinc Complexes and Neutral Phosphinimines for Ring Opening Polymerization of Lactides

Author : Rajesh Thapa
Publisher :
ISBN 13 :
Total Pages : 271 pages
Book Rating : 4.:/5 (936 download)

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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.

New High-activity Zinc(II)-based Catalysts for Ring-opening Polymerization

Author : Ming Cheng
Publisher :
ISBN 13 :
Total Pages : 458 pages
Book Rating : 4.E/5 ( download)

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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:

Studies of Single-site Zinc, Magnesium and Calcium Catalyst Precursors for Ring-Opening Polymerization of Lactides

Author : Khamphee Phomphrai
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (532 download)

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Book Synopsis Studies of Single-site Zinc, Magnesium and Calcium Catalyst Precursors for Ring-Opening Polymerization of Lactides by : Khamphee Phomphrai

Download or read book Studies of Single-site Zinc, Magnesium and Calcium Catalyst Precursors for Ring-Opening Polymerization of Lactides written by Khamphee Phomphrai and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The preparation and characterization of a series of closely related magnesium and zinc compounds active for ROP of lactides are reported using three [beta]-diiminate ligands L 1, L 2 and L 3 where L 1 = CH(CMeNC 6 H 3 -2,6- i Pr 2) 2, L 2 = CH(CMeNC 6 H 4 -2- t Bu) 2 and L 3 = CH(CMeNC 6 H 4 -2-OMe) 2 . For the L 1 ligand, L 1 Mg(N i Pr 2)·(THF), L 1 Zn(N i Pr 2), L 1 Mg(O t Bu)·(THF), L 1 Zn(O t Bu) and L 1 Zn(OSiPh 3)·(THF) have been synthesized. All compounds initiate and sustain ROP of lactides. For a related series L 1 MX(THF) n, where n = 0 or 1, the reactivity follows the order M = Mg> Zn and X = O t Bu> N i Pr 2> N(SiMe 3) 2> OSiPh 3 . Heterotactic polylactide (PLA) is produced from ROP of rac-lactide by zinc catalysts in CH 2 Cl 2 . Magnesium catalysts produce atactic and heterotactic PLA in CH 2 Cl 2 and THF, respectively. The resting states for Zn and Mg are proposed to be L 1 Zn(nu 2 -OCHMeC(O)OP) and L 1 Mg(mu-OP) 2 MgL 1 . For the L 2 ligand, L 2 MgN i Pr 2 ·(THF) and L 2 ZnN i Pr 2 are prepared. In solution, L 2 ZnN i Pr 2 exists as a mixture of syn- and anti-rotamers while L 2 MgN i Pr 2 ·(THF) exists only as a syn-rotamer. In the zinc compound, the syn-conformer is shown to be more reactive than the anti-conformer and is responsible for the polymerization. Heterotactic PLA is obtained in CH 2 Cl 2 for the zinc compound and in THF for the magnesium compound. For the L 3 ligand, L 3 MgN(SiMe 3) 2, [L 3 MgO t Bu] 2, L 3 ZnN(SiMe 3) 2, L 3 ZnO i Pr and L 3 CaN(SiMe 3) 2 ·(THF) are prepared. The OMe groups of ligand L 3 show little affinity toward zinc and in the ROP of rac-lactide give PLA with only moderately enhanced heterotactic tetrads. The OMe groups are shown to bind to Mg reversibly and display significant enhancement of heterotactic PLA. The first single-site calcium complexes of L 1 and tris(pyrazolyl/indazolyl)borate ligands are reported and shown to initiate and sustain ROP of lactide: L 1 CaNR 1 2 ·(THF), Tp R2 CaNR 1 2 ·(THF) n, Tp Men CaNR 1 2, (9-BBN)Bp (+)-Cam CaNR 1 2 ·2THF where Tp R2 = [nu 3 -HB(3-R 2 pz) 3], R 1 = SiMe 3, R 2 = t Bu or i Pr, n = 0 or 1, Men = menthone-derived indazole and Cam = camphor-derived indazole. All calcium complexes polymerize rac-lactide in THF giving mostly atactic PLA except for Tp tBu CaNR 1 2 where heterotactic PLA is produced. Tp tBu CaNR 1 2 reacts with 2,6-diisopropylphenol giving Tp tBu Ca(O-2,6- i Pr 2 C 6 H 3). The order of heterotactic selectivity is THF> PO approx CHO> CH 2 Cl 2 . The single-site calcium complexes are not active for ROP of epoxides and the compound Tp tBu Ca(O-2,6- i Pr 2 C 6 H 3)·(PO) is reported and structurally characterized by a single crystal X-ray diffraction study.

Biometal Catalyzed Ring-opening Polymerization of Cyclic Esters

Author : Osit Karroonnirun
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (85 download)

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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.

Synthesis of Al and Zn Complexes, and Their Catalytic Activity Toward the Ring-opening Polymerization of Cyclic Esters

Author : K. Bakthavachalam
Publisher :
ISBN 13 :
Total Pages : 338 pages
Book Rating : 4.:/5 (995 download)

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Book Synopsis Synthesis of Al and Zn Complexes, and Their Catalytic Activity Toward the Ring-opening Polymerization of Cyclic Esters by : K. Bakthavachalam

Download or read book Synthesis of Al and Zn Complexes, and Their Catalytic Activity Toward the Ring-opening Polymerization of Cyclic Esters written by K. Bakthavachalam and published by . This book was released on 2014 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Synthesis and Characterization of Zinc and Calcium Complexes: Efficient Catalysts for Ring-Opening Polymerization of E-Caprolactone and Lactides

Download Synthesis and Characterization of Zinc and Calcium Complexes: Efficient Catalysts for Ring-Opening Polymerization of E-Caprolactone and Lactides PDF Online Free

Author :
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (137 download)

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Book Synopsis Synthesis and Characterization of Zinc and Calcium Complexes: Efficient Catalysts for Ring-Opening Polymerization of E-Caprolactone and Lactides by :

Download or read book Synthesis and Characterization of Zinc and Calcium Complexes: Efficient Catalysts for Ring-Opening Polymerization of E-Caprolactone and Lactides written by and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Synthesis and Structures of Tridentate Ketoiminate Zinc Complexes Bearing Trifluoromethyl Substituents that Act as L-lactide Ring Opening Polymerization Catalysts

Download Synthesis and Structures of Tridentate Ketoiminate Zinc Complexes Bearing Trifluoromethyl Substituents that Act as L-lactide Ring Opening Polymerization Catalysts PDF Online Free

Author : Nomaan M. Rezayee
Publisher :
ISBN 13 :
Total Pages : 152 pages
Book Rating : 4.:/5 (813 download)

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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:

Late Transition Metal Polymerization Catalysis

Author : Bernhard Rieger
Publisher : Wiley-VCH Verlag GmbH
ISBN 13 :
Total Pages : 360 pages
Book Rating : 4.3/5 (91 download)

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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 Verlag GmbH. This book was released on 2003 with total page 360 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.

Synthesis, Characterization and Immoblization of Solvent Ligated Complexes and Their Catalytic Activity

Author : Ahmed Kamal Hijazi
Publisher :
ISBN 13 : 9783899634532
Total Pages : 130 pages
Book Rating : 4.6/5 (345 download)

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Book Synopsis Synthesis, Characterization and Immoblization of Solvent Ligated Complexes and Their Catalytic Activity by : Ahmed Kamal Hijazi

Download or read book Synthesis, Characterization and Immoblization of Solvent Ligated Complexes and Their Catalytic Activity written by Ahmed Kamal Hijazi and published by . This book was released on 2006 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Zinc and Zirconium Catalysts in Rac-lactide Polymerization

Author : Fatemeh Dordahan
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (131 download)

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Book Synopsis Zinc and Zirconium Catalysts in Rac-lactide Polymerization by : Fatemeh Dordahan

Download or read book Zinc and Zirconium Catalysts in Rac-lactide Polymerization written by Fatemeh Dordahan and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The phenoxy-imine ligand bearing heteroatom-containing N and O were prepared from condensation of paraformaldehyde, 4-(tert-butyl)-2-tritylphenol with di-(2-picolyl)amine. LZnN(SiMe3)2 was prepared by reaction of Zn(N(SiMe3)2)2 and the ligand. The complex has been studied by X-ray diffraction and NMR. Application of this complex in rac-lactide polymerization gave atactic PLA via a catalytic-site mediated chain-end control mechanism. Pyridylaminophenol ligands were prepared from phenol (2,4-di-tert-butylphenol, 2,4-di-cholorolphenol, 2,4-di-methylphenol), pyridine-2-ylmethylamine and formaldehyde (LH2 = (2,4-X2C6(OH)H2(5-CH2)2N(CH2C5H4N), X = Me or Cl). Reaction of Zr(OnPr)4 with 2 equiv of LH2 gave L2Zr. L2Zr were mixtures of C2-symmetric isomers, which was confirmed by NMR, DFT and X-ray diffraction studies. The only isomer for X=Me was the cis-isomer while the major isomer for X=Cl was the trans-isomer. All complex were active in rac-lactide polymerization at 140 °C and heterotactic PLA was obtained. L2Zr followed an activated monomer mechanism with benzyl alcohol as co-initiator.

The Development of Cationic Zinc Complexes as a New Class of Lactide Polymerization Catalyst

Author : Craig Andrew Wheaton
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (13 download)

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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:

Quinoxaline Schiff Base Complexes & Their Catalytic Activity Studies

Author : Vasudevan Nair Arun
Publisher : LAP Lambert Academic Publishing
ISBN 13 : 9783659794698
Total Pages : 244 pages
Book Rating : 4.7/5 (946 download)

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Book Synopsis Quinoxaline Schiff Base Complexes & Their Catalytic Activity Studies by : Vasudevan Nair Arun

Download or read book Quinoxaline Schiff Base Complexes & Their Catalytic Activity Studies written by Vasudevan Nair Arun and published by LAP Lambert Academic Publishing. This book was released on 2015-10-22 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research work deals with studies on the synthesis, characterization and catalytic activities of some transition metal complexes of the Schiff bases derived from 3-hydroxyquinoxaline-2-carboxaldehyde. Schiff bases which are considered as 'privileged ligands' have the ability to stabilize different metals in different oxidation states and thus regulate the performance of metals in a large variety of catalytic transformations. The catalytic activity of the Schiff base complexes is highly dependant on the environment about the metal center and their conformational flexibility. Therefore it is to be expected that the introduction of bulky substituents near the coordination sites might lead to low symmetry complexes with enhanced catalytic properties. With this view new transition metal complexes of Schiff bases derived from 3-hydroxyquinoxaline-2-carboxaldehyde have been synthesised. These Schiff bases have more basic donor nitrogen atoms and the presence of the quinoxaline ring may be presumed to build a favourable topography and electronic environment in the immediate coordination sphere of the metal.

Synthesis, Characterization, and Applications of Mono([mu]-alkoxo)bis(alkylaluminum) Catalysts for Epoxide Polymerization

Author : Jennifer Francesca Imbrogno
Publisher :
ISBN 13 :
Total Pages : 402 pages
Book Rating : 4.:/5 (126 download)

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Book Synopsis Synthesis, Characterization, and Applications of Mono([mu]-alkoxo)bis(alkylaluminum) Catalysts for Epoxide Polymerization by : Jennifer Francesca Imbrogno

Download or read book Synthesis, Characterization, and Applications of Mono([mu]-alkoxo)bis(alkylaluminum) Catalysts for Epoxide Polymerization written by Jennifer Francesca Imbrogno and published by . This book was released on 2021 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in medicine, membranes for gas separations, and batteries have been made possible through associated advances in polyether materials. Further advances will be enabled by continued materials innovation enabled by advances in polymerization catalysis. Polyethers, derived from epoxides, represent a versatile class of functional polymeric materials with the potential for true compositional control of structure-property relationships in a macromolecular platform due to the high thermodynamic ring-strain driving force for polymerization. Despite this promise, there is currently no consensus polymerization technique available for epoxides that provides access to polyether materials with consistently controlled molecular weights, chain-end functionality, tolerance to monomer functionality, and is available to the non-specialist. The Vandenberg catalyst is a well-established, empirically developed, industrial catalyst solution for polyether-based elastomers derived from epoxides. Investigation of compositionally related complexes led to the discovery of well-defined mono(μ-alkoxo)bis(alkylaluminum) (MOB) complexes which function as effective catalyst/initiator for epoxide polymerizations, capable of producing > 10 kg/mol polyethers in minutes depending on MOB composition and epoxide monomer. Variation of alkylaluminum used in the MOB synthesis led to a four-fold variation in polymerization rate, whereas variation of N,N′-alkylamino-ethanol structure led to a 400-fold variation in polymerization rate of epichlorohydrin. The MOB structure appeared to rearrange and dimerize upon addition of polar compounds, E.g., epoxide monomers, revealing an aluminum alkoxide as the site of monomer addition and a N-Al Lewis pair functioning as catalyst. With new epoxide polymerization catalyst in hand, a series of investigations into new polymer structure and compositions was possible. Chain-extension polymerizations were conducted from poly(ethylene oxide) macroinitiators to create block polymer materials, whose architecture and solution self-assembly were investigated. Atactic polyethers exhibiting semi-crystallinity mediated by long alkyl side chains were synthesized and studied as phase-change materials. Finally, our synthetic advances enabled a fundamental study of polymer electrolyte structure-property relationships by varying dielectric constants among a series of homologous polymer structures revealing the important role of polarity in dictating ion transport properties. These studies highlight the enabling role of new polymerization catalysis in materials science and engineering

Studies Towards Degradable Polymers

Author : Peter Malatji
Publisher :
ISBN 13 :
Total Pages : 200 pages
Book Rating : 4.:/5 (843 download)

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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:

Bio-inspired Trinuclear Zinc(II) Complexes as Models for Hydrolytic Metallo-enzymes

Author : Ranjan Mitra
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (66 download)

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Book Synopsis Bio-inspired Trinuclear Zinc(II) Complexes as Models for Hydrolytic Metallo-enzymes by : Ranjan Mitra

Download or read book Bio-inspired Trinuclear Zinc(II) Complexes as Models for Hydrolytic Metallo-enzymes written by Ranjan Mitra and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Phosphodiesterase enzymes, such as phospholipase C and nuclease P1, use three Zn(II) ions in their active site to catalyze the hydrolytic cleavage of phosphate diester bonds in phospholipids and in nucleotides such as single-stranded DNA/RNA, respectively. However, the function of the zinc triad is still not well understood. Functional mimics of phosphoesterases are important for understanding the role of metal ions in the hydrolytic mechanism and for developing artificial nucleases for biochemical and medicinal applications. Inspired by these trinuclear Zn(II) sites in enzymatic systems, a C3 -symmetric trinuclear Zn(II) hydroxide complex was synthesized using a triphenoxymethane platform. This complex induces a 16,900-fold rate enhancement in the catalytic cyclization of the RNA model substrate, 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP, pH 6.7, 25°C) over the uncatalyzed reaction with multiple turnovers. The observed differences in the pH-rate profile can be attributed to the varying concentration of various trinuclear zinc species. The trinuclear Zn(II) catalyst exhibits a higher hydrolytic activity compared to its mononuclear analogue. The reactivity and structural features of this trinuclear Zn(II) complex will be discussed. Since subtle differences in the mutual arrangement/orientation of the metal binding arms have a crucial influence on the intrinsic activity of the trinuclear Zn(II) complexes, development of a ligand system wherein the metal binding arms are directly attached to the aromatic ring was undertaken. Extensive exploration aimed at functionalization of the para-position of the triphenoxymethane platform led to the successful synthesis of two C3-symmetric triphenoxymethane based Schiff-base ligands. The synthesis of these ligands and their zinc complexes along with the structural characterization of these complexes are presented herein.

Metalorganic Catalysts for Synthesis and Polymerization

Author : Walter Kaminsky
Publisher : Springer
ISBN 13 :
Total Pages : 696 pages
Book Rating : 4.3/5 (91 download)

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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.