The Experts below are selected from a list of 8097 Experts worldwide ranked by ideXlab platform
Sebastien Perrier - One of the best experts on this subject based on the ideXlab platform.
-
original approach to multiblock copolymers via reversible addition fragmentation Chain Transfer polymerization
Journal of Polymer Science Part A, 2007Co-Authors: Hesna Gemici, Thomas M Legge, Michael R Whittaker, Michael J Monteiro, Sebastien PerrierAbstract:A study was conducted to demonstrate reversible Chain-Transfer Agent (CTA) polymerization of telechelic polymethyl methacrylate (PMMA) copolymers. The reaction was mixture was stirred at 60 °C for 24 hours and the polymer was purified by passing it through basic alumina before the precipitation in methanol, after the reaction. The resultant product was precipitated in methanol after the reaction was stopped and ultraviolet-vis (UV) spectroscopy was used to show that all the dithioester groups were converted into thiols through aminolysis.
-
raft graft polymerization of 2 dimethylaminoethyl methacrylate onto cellulose fibre
Australian Journal of Chemistry, 2006Co-Authors: Debashish Roy, J T Guthrie, Sebastien PerrierAbstract:Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) was grafted from cellulose by reversible addition–fragmentation Chain Transfer (RAFT) polymerization. The use of a free Chain Transfer Agent in solution allowed for a better control over graft ratio, Chain length of grafted polymer, monomer conversion, and homopolymer formation in solution. An increase in polymerization time or degree of polymerization led to an increase in graft ratio, as expected from a living system.
-
influence of reaction parameters on the synthesis of hyperbranched polymers via reversible addition fragmentation Chain Transfer raft polymerization
Polymer, 2005Co-Authors: Algy Kazlauciunas, J T Guthrie, Sebastien PerrierAbstract:Abstract The synthesis of hyperbranched poly(methyl methacrylate) (PMMA) via reversible addition fragmentation Chain Transfer (RAFT) polymerization was investigated by varying the ratio Chain Transfer Agent (CTA): monomer (methyl methacrylate, MMA): brancher (ethylene glycol dimethyl methacrylate, EGDMA): free radical initiator (AIBN) at various temperatures (50, 55, 60, 65, 70 °C). The rate of polymerization was observed to increase with temperature and concentration in brancher, whilst it was lowered by an increase in Chain Transfer Agent concentration. The molecular weight of the samples increased with the ratios brancher: CTA and monomer: CTA. The polydispersity of the samples increase with conversion, as the level of branching increases. At fixed concentration in brancher, an increase of CTA concentration led to polymers with lower PDI. The variation of enthalpy ( Δ H ¯ m ) and entropy ( Δ S ¯ m ) relative to the monomer reaction were calculated, and it was observed that an increase in the brancher concentration induced an increase in both Δ H ¯ m and Δ S ¯ m , whilst lower CTA concentrations led to an increase in Δ S ¯ m . The variation in Gibbs energy for the monomer reaction ( Δ G ¯ m ) was calculated at 60 °C, and results confirmed the presence of a retardation effect when increasing CTA concentration generally observed in RAFT polymerization.
Timothy F. L. Mckenna - One of the best experts on this subject based on the ideXlab platform.
-
investigation of the Chain Transfer Agent effect onthe polymerization of vinylidene fluoride
Industrial & Engineering Chemistry Research, 2019Co-Authors: Igor Stefanichen Monteiro, Ana Carolina Mendez Ecoscia, Timothy F. L. MckennaAbstract:The effect of Chain Transfer Agents (CTAs) ethyl acetate (EA), octyl acetate (OA), and isopropyl alcohol (IPA) on the rate of polymerization of vinylidene fluoride (VDF) in an emulsion polymerization and in solution polymerization in dimethyl carbonate (DMC) initiated by tert-butyl peroxypivalate was investigated. Pressure profiles of the polymerizations were recorded. Solids content and rate of polymerization were calculated by gravimetry; size exclusion chromatography was utilized to evaluate CTA activity, and the produced polymer microstructures were characterized by 1H and 19F NMR spectroscopies. It is proposed that the observed reduction in polymerization rate in both systems is due to degradative Chain Transfer reactions.
-
synthesis of acrylic polyurethane hybrid latexes by miniemulsion polymerization and their pressure sensitive adhesive applications
Macromolecules, 2011Co-Authors: Ravindra Udagama, Elise Degrandicontraires, Christian Graillat, Timothy F. L. Mckenna, Costantino Creton, Elodie BourgeatlamiAbstract:The successful incorporation of a NCO-terminated polyurethane (PU) prepolymer in a hybrid miniemulsion is described with the purpose to develop waterborne, high solids, acrylic−PU hybrid nanoparticles to be used in pressure-sensitive adhesive (PSA) applications. To ensure efficient chemical incorporation of the reactive PU into the hybrid latex particles, the NCO moieties were reacted with 2-hydroxyethyl methacrylate (HEMA). The NCO−HEMA coupling reaction was thoroughly studied by conductimetry in order to control the extent of HEMA incorporation into the PU Chains. The resulting HEMA-end-capped prepolymers were Chain extended in situ with Bisphenol A (BPA) and polymerized with n-butyl acrylate, methyl methacrylate, and acrylic acid in the presence of small amounts of a Chain Transfer Agent to form PU/acrylic particles. The amount of Chain Transfer Agent, the ratio between HEMA and BPA, and the amount of PU were varied step by step to study their influence on the final film properties. The miniemulsions a...
Shigeru Yamago - One of the best experts on this subject based on the ideXlab platform.
-
tacticity molecular weight and temporal control by lanthanide triflate catalyzed stereoselective radical polymerization of acrylamides with an organotellurium Chain Transfer Agent
Polymer Chemistry, 2020Co-Authors: Yuji Imamura, Takehiro Fujita, Yu Kobayashi, Shigeru YamagoAbstract:Dual control over molecular weight and tacticity in the polymerization of N,N-dimethylacyrlamide, N,N-diethylacrylamide, N-isopropylacrylamide, and acrylamide was achieved by organotellurium-mediated radical polymerization (TERP) in the presence of Y(OTf)3 or Yb(OTf)3 as a Lewis acid catalyst. While previous dual-control reactions have been limited to the synthesis of low-molecular-weight polyacrylamides, the current conditions significantly expanded this limitation. The high compatibility of the TERP Chain Transfer Agent and dormant species to the Lewis acid was demonstrated by nearly complete end-group fidelity. Stereoblock copolymers consisting of atactic and isotactic PDEAA blocks were also successfully synthesized. Temporal control while maintaining dual control was also achieved by using photoactivation of organotellurium species. The effect of tacticity on the polymer structure in the gas phase was estimated for the first time by ion mobility spectrometry, revealing that the collision cross section increased as the meso diad selectivity of the polyacrylamide increased.
-
living ab initio emulsion polymerization of methyl methacrylate in water using a water soluble organotellurium Chain Transfer Agent under thermal and photochemical conditions
Angewandte Chemie, 2018Co-Authors: Weijia Fan, Masatoshi Tosaka, Shigeru Yamago, Michael F CunninghamAbstract:Ab initio emulsion polymerization of methyl methacrylate (MMA) using a water-soluble organotellurium Chain Transfer Agent in the presence of the surfactant Brij 98 in water is reported. Polymerization proceeded under both thermal and visible light-irradiation conditions, giving poly(methyl methacrylate) (PMMA) with controlled molecular weight and low dispersity (Đ<1.5). Despite the formation of an opaque latex, the photoactivation of the organotellurium dormant species took place efficiently, as demonstrated by the quantitative monomer conversion and temporal control. Control of polymer particle size (PDI<0.030) was also achieved using a semi-batch monomer addition process. The PMMA polymer in the particles retained high end-group fidelity and was successfully used for the synthesis of block copolymers.
-
organotellurium mediated controlled living radical polymerization initiated by direct c te bond photolysis
Journal of the American Chemical Society, 2009Co-Authors: Shigeru Yamago, Yuu Ukai, Atsushi Matsumoto, Yasuyuki NakamuraAbstract:UV−vis irradiation of an organotellurium Chain Transfer Agent in the presence of vinyl monomers leads to the formation of highly controlled living polymers with predetermined number average molecular weights and narrow molecular weight distributions.
Jason J Davis - One of the best experts on this subject based on the ideXlab platform.
-
ultrasensitive impedimetric immunosensor for the detection of c reactive protein in blood at surface initiated reversible addition fragmentation Chain Transfer generated poly 2 hydroxyethyl methacrylate brushes
Analytical Chemistry, 2020Co-Authors: Prosper Kanyong, Candan Catli, Jason J DavisAbstract:The reversible addition–fragmentation Chain Transfer (RAFT) polymerization of 2-hydroxethyl methacrylate (HEMA) from a surface confined, dithio-tethered, Chain Transfer Agent (CTA) enables the prep...
Caiyuan Pan - One of the best experts on this subject based on the ideXlab platform.
-
dendrimer star polymer and block copolymer prepared by reversible addition fragmentation Chain Transfer raft polymerization with dendritic Chain Transfer Agent
Journal of Polymer Science Part A, 2005Co-Authors: Chunyan Hong, Jun Liu, Yezi You, Caiyuan PanAbstract:A new reversible addition-fragmentation Chain Transfer (RAFT) Agent, dendritic polyester with 16 dithiobenzoate terminal groups, was prepared and used in the RAFT polymerization of styrene (St) to produce star polystyrene (PSt) with a dendrimer core. It was found that this polymerization was of living characters, the molecular weight of the dendrimer-star polymers could be controlled and the polydispersities were narrow. The dendrimer-star block copolymers of St and methyl acrylate (MA) were also prepared by the successive RAFT polymerization using the dendrimer-star PSt as macro Chain Transfer Agent. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6379–6393, 2005
-
dihydroxyl terminated telechelic polymers prepared by raft polymerization using functional trithiocarbonate as Chain Transfer Agent
Polymer, 2004Co-Authors: Jun Liu, Chunyan Hong, Caiyuan PanAbstract:Abstract A novel reversible addition–fragmentation Chain Transfer (RAFT) Agent, S,S′-bis(2-hydroxylethyl-2′-butyrate)trithiocarbonate (BHEBT), was first successfully synthesized in the presence of an anion-exchange resin with OH− form, and then it was used as Chain Transfer Agent in RAFT polymerizations of styrene or methyl acrylate, the dihydroxyl-terminated polymers with controlled molecular weights and narrow molecular weight distributions were produced, which was confirmed by GPC, 1H NMR spectra and kinetic analysis. Furthermore, these obtained telechelic polymers with trithiocarbonate group in the middle of the Chains were used as macro Chain Transfer Agents in the further RAFT polymerizations, and well-defined telechelic dihydroxyl-terminated triblock copolymers have been prepared successively. The structures were confirmed by their IR and 1H NMR spectra.