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Ring-Opening Polymerization (Ring-Open + polymerization)
Selected AbstractsA Family of 1,1,3,3-Tetraalkylguanidine (H-TAG) Solvated Zinc Aryloxide Precatalysts for the Ring-Opening Polymerization of rac -LactideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2010Julia J. Ng Abstract Reaction of [Zn(,-TAG){N(SiMe3)2}]2 {TAG = N=C[N(CH2CH3)2N(CH3)2] (DEDMG), N=C{[NCH2CH2CH2CdH2(N,Cd)]N(CH2CH3)2} (DEPYRG) and N=C{[NCH2CH2CH2CH2CeH2(N,Ce)]N(CH2CH3)2} (DEPIPG)} with 2 equiv. of ethanol (EtOH) and 2 equiv. of HOAr {OAr = OC6H3(CMe3)-2-(CH3)-6 (BMP) or OC6H2[C(CH3)3]2 -2,6-(CH3)-4 (4MeDBP)} results in dizinc alkoxides with the general formula [Zn(,-OEt)(OAr)(H-TAG)]2 (1,3). Et2Zn was additionally treated with 2 equiv. of 1,1,3,3-tetramethylguanidine (H-TMG) and H-BMP or HOC6H3(C6H5)2 -2,6 to yield [Zn(BMP)2(H-TMG)2] (4) and [Zn{OC6H3(C6H5)2 -2,6}2(H-TMG)2] (5). Complexes 1, 2, 4, and 5 were characterized by single-crystal X-ray diffraction. Polymerization of rac -lactide with 1,5 and [Zn(,-OMe)(4MeDBP)(H-TMG)]2 (6) were found to generate polylactide (PLA). The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FTIR spectroscopy, and 1H and 13C NMR spectroscopic studies. [source] First Example of a Gold(I) N -Heterocyclic-Carbene-Based Initiator for the Bulk Ring-Opening Polymerization of L -LactideEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2006Lipika Ray Abstract Synthesis, structure, and catalysis studies of two Au- and Ag-based initiators, namely, [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AuCl (1c) and [3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazol-2-ylidene]AgCl (1b), for the bulk ring-opening polymerization of L -lactide are reported. Specifically, gold complex 1c was obtained from silver complex 1b by the transmetalation reaction with (SMe2)AuCl. Silver complex 1b was synthesized by the treatment of 3-(N - tert -butylacetamido)-1-(2-hydroxycyclohexyl)imidazolium chloride (1a) with Ag2O. Compound 1a was synthesized directly from the reaction of N - tert -butyl-2-chloroacetamide, cyclohexene oxide, and imidazole. The molecular structures of 1a, 1b, and 1c have been determined by X-ray diffraction studies. The formation of neutral monomeric complexes with linear geometries at the metal centers was observed for both 1b and 1c. The Au and Ag complexes 1c and 1b successfully catalyzed the bulk ring-opening polymerization of L -lactide at elevated temperatures under solvent-free melt conditions to produce moderate to low molecular weight polylactide polymers with narrow molecular weight distributions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Low-Distortion Holographic Data Storage Media Using Free-Radical Ring-Opening PolymerizationADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Kyongsik Choi Abstract Holographic data storage, due to its potential to increase capacity beyond one terabyte per disk, is tipped to be one of the next generation optical data storage technologies. Polymer-based systems are leading candidates due to their high dynamic range, high sensitivities, and flexible and easy production, and yet polymerization-shrinkage-induced distortion is a major hurdle for its reliable use. In this paper, a new free radical polymerization holographic recording medium, based on low shrink cyclic allylic sulfides (LS-CASs) ring-opening monomers, is proposed and demonstrated. The percentage of volume shrinkage is measured to be 0.02%, with refractive index (RI) contrast of (1.01,±,0.5),×,10,3. The measured volume shrinkage is, to the authors' best knowledge, the best reported so far in the literature. Other parameters such as sensitivity, dynamic range, and dark reaction properties are also measured, where the values can be optimized with high RI functional groups without sacrificing the low shrinkage. [source] Lipase-Catalyzed Ring-Opening Polymerization of Molecularly Pure Cyclic Oligomers for Use in Synthesis and Chemical Recycling of Aliphatic PolyestersMACROMOLECULAR BIOSCIENCE, Issue 6 2008Asato Kondo Abstract The lipase-catalyzed ROP of molecularly pure cyclic oligomers with a definite degree of oligomerization is analyzed with respect to the molecular weights of the resulting polymers and certain kinetic parameters of the enzymatic reaction. Cyclic BA dimers, trimers, and tetramers polymerize faster than the equivalent monomer; however, the latter produces PBA of significantly higher molecular weight. The reason is that the ring opening of the cyclic monomer is slow, leading to a lower initiator concentration than that produced by the cyclic BA dimer and trimer. Similarly, the cyclic BS dimer produces PBS of higher molecular weight than that obtained from the cyclic BS trimer. [source] Preparation of Poly(, -caprolactone)/Clay Nanocomposites by Microwave-Assisted In Situ Ring-Opening PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2007Liqiong Liao Abstract PCL/clay nanocomposites were prepared by microwave-assisted in situ ROP of , -caprolactone in the presence of either unmodified clay (Cloisite® Na+) or clay modified by quaternary ammonium cations containing hydroxyl groups (Cloisite 30B). This PCL showed significantly improved monomer conversion and molecular weight compared with that produced by conventional heating. An intercalated structure was observed for the PCL/Cloisite Na+ nanocomposites, while a predominantly exfoliated structure was observed for the PCL/Cloisite 30B nanocomposites. Microwave irradiation proved to be an effective and efficient method for the preparation of PCL/clay nanocomposites. [source] Influence of Microwave Irradiation on the Lipase-Catalyzed Ring-Opening Polymerization of , -CaprolactoneMACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2006Patrick Kerep Abstract Summary: The microwave (MW)-assisted lipase-catalyzed ring-opening polymerization of , -caprolactone in boiling solvents was investigated for the first time. In case of boiling toluene or benzene the MW-assisted reaction proceeded significantly slower compared to oil bath heating. On the other hand, using boiling diethyl ether as solvent, an increase of the polymerization rate due to MW irradiation was found. Yield, molecular weight measurements, and MALDI-TOF analysis supported the results. Reactivity of the MW-assisted ring-opening polymerization of , -caprolactone compared with conventional thermal heating in different solvents. [source] Living Ring-Opening Polymerization of Cyclic Esters with Epoxide-Derived Titanium Alkoxides,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2005Alexandru D. Asandei Abstract Summary: The TiIIICp2Cl-catalyzed radical ring opening of epoxides produces Ti alkoxides which initiate the ring-opening polymerization of , -caprolactone. A linear dependence of on conversion, linear kinetics, low values, and the synthesis of block copolymers demonstrate a living process, while NMR spectroscopy confirms the presence of the initiator chain end. Epoxides are thus introduced as a new class of initiators for the Ti-catalyzed living ring-opening polymerization of cyclic esters. The TiCp2Cl-catalyzed radical ring opening of epoxides followed by the initiation of the living ring-opening polymerization of , -caprolactone. [source] Addition-Fragmentation Chain Transfer to Polymer in the Free Radical Ring-Opening Polymerization of an Eight-membered Cyclic Allylic Sulfide MonomerMACROMOLECULAR THEORY AND SIMULATIONS, Issue 2 2005Marisa Phelan Abstract Summary: A detailed investigation of chain transfer to polymer during free radical ring-opening polymerization of the eight-membered disulfide monomer 2-methyl-7-methylene-1,5-dithiacyclooctane (MDTO) is presented. It has been shown that extensive chain transfer to polymer occurs involving both poly(MDTO) radicals and cyanoisopropyl radicals. Significant decreases in molecular weight were observed when cyanoisopropyl radicals were generated in the presence of poly(MDTO) in the absence of monomer. The molecular weight distribution (MWD) obtained from polymerization of MDTO in the presence of pre-added poly(MDTO) was markedly different from that obtained without pre-added polymer. A kinetic model was constructed in an attempt to quantitatively describe the chain transfer to polymer process based on the addition fragmentation chain transfer mechanism. It was found however that the simulated MWDs were considerably broader than the experimental MWDs, which were similar to the Schulz-Flory distribution. Mechanism for chain transfer to polymer. [source] Handbook of Ring-Opening Polymerization.ANGEWANDTE CHEMIE, Issue 52 2009Herausgegeben von Philippe Dubois, Olivier Coulembier und Jean-Marie Raquez. Wiley-VCH, Weinheim 2009. 408,S., geb., 149.00,,.,ISBN 978-3527319534 [source] Metal Triflates as Highly Stable and Active Catalysts for the "Immortal" Ring-Opening Polymerization of Trimethylene CarbonateCHEMCATCHEM, Issue 3 2010Marion Helou Abstract The controlled "immortal" ring-opening polymerization of trimethylene carbonate (TMC) using a two-component catalyst system based on a metal Lewis acid, such as a metal triflate M(OTf)n(M=Ca, Sc, Zn, Al, Bi; OTf=CF3SO3,) or the metallic salt Fe(acac)3, (acac=acetylacetonate) and an alcohol (ROH) as co-initiator and chain-transfer agent, is carried out in bulk at 110,150,°C. As a result of the water-tolerance of these systems, experimental operating conditions do not require any special care. The approach, valorized both with various ROH transfer agents and with either purified or unpurified monomer sources, is highly versatile. Functional telechelic polycarbonates HPTMCOR, devoid of decarboxylation sequences, are obtained [PTMC=poly(trimethylene carbonate)]. The molar mass of the PTMCs can be readily predicted by a simple model, taking into account the [TMC]0/[ROH]0 ratio and the amount of transferring impurities present in the raw/unpurified reagents. Such simple, air- and moisture-robust catalytic systems, which display quite high activities (TOF up to 28,200,h,1) and productivities (TON up to 45,000) are thus extremely valuable, especially industrially. The performances of these systems are described in comparison to the previously established valuable inorganic and organometallic catalytic systems, namely metal amido complexes ([M{N(SiMe3)2}3]) and [(BDI)Zn{N(SiMe3)2}] (BDI=,-diiminate ligand) derivatives. [source] One-Pot Synthesis of Lactide,Styrene Diblock Copolymers via Catalytic Immortal Ring-Opening Polymerization of Lactide and Nitroxide-Mediated Polymerization of StyreneCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 5 2010Valentin Poirier Abstract An efficient, practical, and industrially relevant procedure for the production of polymer materials, in which a part of the oil-derived polyolefins has been replaced by a renewable, biodegradable, and biocompatible poly(lactide) block, is presented. Binary catalytic systems combining innocuous metals (yttrium, zinc, magnesium, or calcium) and bifunctional alcohols (acting as transfer agents) were developed to promote the immortal ring-opening polymerization of lactide directly in styrene. Up to 20,000,equivalents of lactide were polymerized (metal catalyst loading of 50,100,ppm) in a controlled fashion in the presence of 10,100,equivalents of a double-headed transfer agent to give as many end-functionalized poly(lactide) macromolecules that can be used eventually as macroinitiators for the controlled nitroxide-mediated polymerization of styrene. The specific use of the sterically shielded complex [BDI- iPr]Zn-N(SiMe3)2 ([BDI- iPr]=bis(diketiminate) ligand) allowed the efficient, catalytic, and controlled production of poly(lactide)- block -poly(styrene) materials in a one-pot, solvent-free sequential procedure, with nearly 100,% atom-efficiency. [source] | |||||||||||||