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RAFT Polymerization (raft + polymerization)
Selected AbstractsA Novel Strategy to Synthesize Double Comb-Shaped Water Soluble Copolymer by RAFT PolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006De-Hui Han Abstract Summary: A double comb-shaped water soluble copolymer, poly[poly(ethylene oxide) methyl ether methacrylate]- block -poly(N -isopropylacrylamide)- block -poly[poly (ethylene oxide) methyl ether methacrylate], abbreviated as [P(MA-MPEO)- block -PNIPAM- block -P(MA-MPEO)], with a controlled molecular weight and narrow polydispersity was successively synthesized using a macromonomer technique. The 60Co , irradiation polymerization of MA-MPEO in the presence of dibenzyl trithiocarbonate (DBTTC) at room temperature afforded a polymer, P(MA-MPEO)-SC(S)S-P(MA-MPEO), which was subsequently used as a macro RAFT agent in the RAFT polymerization of N -isopropylacrylamide, and water soluble double comb-shaped copolymers, P(MA-MPEO)- block -PNIPAM- block -P(MA-MPEO), were successfully obtained. Structure of the double comb-shaped copolymer. [source] Additional Retardation in RAFT Polymerization: Detection of Terminated Intermediate RadicalsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 7 2007Maël Bathfield Abstract The reversible addition-fragmentation chain transfer (RAFT) polymerization of N -acryloylmorpholine (NAM) is performed using three dithioesters (DT) as chain transfer agents (CTA) that incorporate a morpholine (morpholine-DT), a biotin (biotin-DT), or a sugar (sugar-DT) moiety in the R group. PolyNAM chains of controlled characteristics are synthesized. An unexpected behavior is observed with morpholine-DT, described as an ,additional retardation', which is especially visible when low molar masses are targeted (,<,5,000 g,·,mol,1). In that particular case, further investigations using MALDI-TOF mass spectrometry show the presence of terminated intermediate radicals (IRs), which corroborates the assumption based on a specific protection of IR according to the nature of the , -chain-end. [source] Modeling of Diffusion Limitations in Bulk RAFT PolymerizationMACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2006A. David Peklak Abstract Summary: The impact of diffusion limitations on RAFT polymerizations is investigated in this work. In particular, two models are compared: one accounting for diffusion limitations by using average chain lengths, the other accounting for the entire CLD. It is shown that such a description is necessary to correctly predict the kinetics of polymerization processes, as well as the evolution of average chain length and polydispersity. For properly selected study cases, differing conversion curves are obtained above 40% monomer conversion, if only average values of the CLD are considered. The same is valid for the calculation of the polydispersity, which starts differing above 80% conversion. Finally, for given conditions of diffusion limitations, it is found that an ideal polydispersity can be defined and it is shown that the polydispersity tends to this characteristic value during the entire evolution of the polymerization process. as a function of f for various values of . [source] Perfluorocyclobutyl-containing Amphiphilic Block Copolymers Synthesized by RAFT PolymerizationCHINESE JOURNAL OF CHEMISTRY, Issue 11 2009Yongjun Chen Abstract Amphiphilic block copolymers containing hydrophobic perfluorocyclobutyl-based (PFCB) polyacrylate and hydrophilic poly(ethylene glycol) (PEG) segments were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. The PFCB-containing acrylate monomer, p -(2-(p -tolyloxy)perfluorocyclobutoxy)-phenyl acrylate, was first synthesized from commercially available compounds in good yields, and this kind of acrylate monomer can be homopolymerized by free radical polymerization or RAFT polymerization. Kinetic study showed the 2,2,-azobis(isobutyronitrile) (AIBN) initiated and cumyl dithiobenzoate (CDB) mediated RAFT polymerization was in a living fashion, as suggested by the fact that the number-average molecular weights (Mn) increased linearly with the conversions of the monomer, while the polydispersity indices kept less than 1.10. The block polymers with narrow molecular weight distributions (Mw/Mn,1.21) were prepared through RAFT polymerization using PEG monomethyl ether capped with 4-cyanopentanoic acid dithiobenzoate end group as the macro chain transfer agent (mPEG-CTA). The length of the hydrophobic segment can be tuned by the feed ratio of the PFCB-based acrylate monomer and the extending of the polymerization time. The micellization behavior of the block copolymers in aqueous media was investigated by the fluorescence probe technique. [source] Ab initio Emulsion Polymerization by RAFT (Reversible Addition,Fragmentation Chain Transfer) through the Addition of CyclodextrinsHELVETICA CHIMICA ACTA, Issue 8 2006Bojana Apostolovic Abstract A novel process to produce homo- and copolymers by RAFT polymerization in emulsion is presented. It is known that RAFT-controlled radical polymerization can be conducted in emulsion polymerization without disturbing the radical segregation characteristic of this process, thus leading to polymerization rates identical to those encountered in the corresponding nonliving systems. However, RAFT agents are often characterized by very low water solubility and, therefore, they diffuse very slowly from the monomer droplets, where they are initially solubilized, to the reaction loci, i.e., the polymer particles. Accordingly, when used in emulsion polymerization, they are practically excluded from the reaction. In this work, we show that cyclodextrins, well-known for their ability to form water-soluble complexes with hydrophobic molecules, facilitate the transport across the H2O phase of the RAFT agent to the polymer particles. Accordingly, chains grow through the entire process in a controlled way. This leads to the production of low-polydispersity polymers with well-defined structure and end functionalities as well as to the possibility of synthesizing block copolymers by a radical mechanism. [source] Immobilization: Reversible Immobilization onto PEG-based Emulsion-templated Porous Polymers by Co-assembly of Stimuli Responsive Polymers (Adv. Mater.ADVANCED MATERIALS, Issue 1 20091/2009) Reversible immobilization onto the surface of highly porous polymers through co-assembly of stimuli-responsive polymers is reported on p. 55 by Neil Cameron and co-workers. Elastin-based side-chain polymers (EBPs) are prepared by RAFT polymerization and attached to the surface of PEG-based emulsion-templated porous polymers. By careful choice of EBP molecular weight and experimental conditions, pH-controlled reversible co-assembly of a complementary EBP from solution is demonstrated. [source] Semibatch RAFT polymerization for producing ST/BA copolymers with controlled gradient composition profilesAICHE JOURNAL, Issue 4 2008Xiaoying Sun Abstract With controlled/living radical copolymerization, the composition profile along polymer chains becomes a tunable parameter in preparing copolymer products for novel materials properties. In this work, a novel series of styrene/butyl acrylate (St/BA) copolymers with precisely designed composition profiles (uniform, linear gradient, tanh gradient, and triblock with a linear gradient mid-block) were produced using a semibatch reversible addition-fragmentation chain transfer copolymerization mediated by benzyl dithioisobutyrate. The comonomer feeding rate was programmed based on a kinetic model with the targeted composition profile as an objective functions. The experimental composition and molecular weight profiles agreed very well with the model predictions. The polymer molecular weight distributions were narrow with polydispersity index values about 1.3. The amount of dead chains was controlled below 10%. The glass transition behaviors of the St/BA copolymers were evaluated and their Tg values were found to be in an order of uniform < linear gradient < tanh gradient < triblock with 10°C for uniform and 140°C for triblock copolymers. © 2008 American Institute of Chemical Engineers AIChE J 2008 [source] Star polymers by cross-linking of linear poly(benzyl- L -glutamate) macromonomers via free-radical and RAFT polymerization.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2010A simple route toward peptide-stabilized nanoparticles Abstract Poly(benzyl- L -glutamate) (PBLG) macromonomers were synthesized by N -carboxyanhydride (NCA) polymerization initiated with 4-vinyl benzylamine. MALDI-ToF analysis confirmed the presence of styrenic end-groups in the PBLG. Free-radical and RAFT polymerization of the macromonomer in the presence of divinyl benzene produced star polymers of various molecular weights, polydispersity, and yield depending on the reaction conditions applied. The highest molecular weight (Mw) of 10,170,000 g/mol was obtained in a free-radical multibatch approach. It was shown that the PBLG star polymers can be deprotected to obtain poly(glutamic acid) star polymers, which form water soluble pH responsive nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Kinetic investigation of the RAFT polymerization of p -acetoxystyreneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2010Solène I. Cauët Abstract The kinetics of the RAFT polymerization of p -acetoxystyrene using a trithiocarbonate chain transfer agent, S -1-dodecyl- S,-(,,,,-dimethyl-,,-acetic acid)trithiocarbonate, DDMAT, was investigated. Parameters including temperature, percentage initiator, concentration, monomer-to-chain transfer agent ratio, and solvent were varied and their impact on the rate of polymerization and quality of the final polymer examined. Linear kinetic plots, linear increase of Mn with monomer conversion, and low final molecular weight dispersities were used as criteria for the selection of optimized polymerization conditions, which included a temperature of 70 or 80 °C with 10 mol % AIBN initiator in bulk for low conversions or in 1,4-dioxane at a monomer-to-solvent volume ratio of 1:1 for higher conversions This study opens the way for the use of DDMAT as a chain transfer agent for RAFT polymerization to incorporate p -acetoxystyrene together with other functional monomers into well-defined copolymers, block copolymers, and nanostructures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2517,2524, 2010 [source] Synthesis of comb polymers via grafting-onto macromolecules bearing pendant diene groups via the hetero-Diels-Alder-RAFT click conceptJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2010Antoine Bousquet Abstract Comb polymers were synthesized by the "grafting-onto" method via a combination of Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization and the hetero-Diels-Alder (HDA) cycloaddition. The HDA reactive monomer trans, trans-hexa-2,4-dienylacrylate (ttHA) was copolymerized with styrene via the RAFT process. Crosslinking was minimized by decreasing the monomer concentration,whilst keeping monomer to polymer conversions low,resulting in reactive backbones with on average one reactive pendant diene groups for 10 styrene units. The HDA cycloaddition was performed between the diene functions of the copolymer and a poly(n -butyl acrylate) (PnBA) prepared via RAFT polymerization with pyridin-2-yldithioformate, which can act as a dienophile. The coupling reactions were performed within 24 h at 50 °C and the grafting yield varies from 75% to 100%, depending on the number average molecular weight of the PnBA (3500 g mol,1 < Mn < 13,000 g mol,1) grafted chain and the reaction stoichiometry. The molecular weights of the grafted block copolymers range from 19,000 g mol,1 to 58,000 g mol,1 with polydispersities close to 1.25. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1773,1781, 2010 [source] Macromolecular brushes synthesized by "grafting from" approach based on "click chemistry" and RAFT polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2010Dongxia Wu Abstract Well-defined macromolecular brushes with poly(N -isopropyl acrylamide) (PNIPAM) side chains on random copolymer backbones were synthesized by "grafting from" approach based on click chemistry and reversible addition-fragmentation chain transfer (RAFT) polymerization. To prepare macromolecular brushes, two linear random copolymers of 2-(trimethylsilyloxy)ethyl methacrylate (HEMA-TMS) and methyl methacrylate (MMA) (poly(MMA- co -HEMA-TMS)) were synthesized by atom transfer radical polymerization and were subsequently derivated to azide-containing polymers. Novel alkyne-terminated RAFT chain transfer agent (CTA) was grafted to polymer backbones by copper-catalyzed 1,3-dipolar cycloaddition (azide-alkyne click chemistry), and macro-RAFT CTAs were obtained. PNIPAM side chains were prepared by RAFT polymerization. The macromolecular brushes have well-defined structures, controlled molecular weights, and molecular weight distributions (Mw/Mn , 1.23). The RAFT polymerization of NIPAM exhibited pseudo-first-order kinetics and a linear molecular weight dependence on monomer conversion, and no detectable termination was observed in the polymerization. The macromolecular brushes can self-assemble into micelles in aqueous solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 443,453, 2010 [source] Synthesis of gradient copolymers with complexing groups by RAFT polymerization and their solubility in supercritical CO2JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009Tiphaine Ribaut Abstract We report the synthesis of new gradient fluorinated copolymers with complexing groups and soluble in supercritical carbon dioxide (scCO2). Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -acetoacetoxyethyl methacrylate) (poly(FDA- co -AAEM)) and poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -vinylbenzylphosphonic acid diethylester) (poly(FDA- co -VBPDE)) gradient copolymers were synthesized by reversible addition fragmentation chain transfer polymerization in ,,,,,-trifluorotoluene. Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate- co -vinylbenzylphosphonic diacid) (poly(FDA- co -VBPDA)) gradient copolymer was efficiently obtained by cleavage of the phosphonic ester groups of poly(FDA- co -VBPDE). The cloud points of these gradient copolymers in dense CO2 were measured in a variable volume view cell at temperatures between 25 and 65 °C. The gradient copolymers show very good solubility in compressed CO2 with the decreasing order: poly(FDA- co -AAEM) , poly(FDA- co -VBPDE) > poly(FDA- co -VBPDA). Following a green chemistry strategy, poly(FDA- co -AAEM) gradient copolymer was successfully synthesized in scCO2 with a good control over number-average molecular weight and composition. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5448,5460, 2009 [source] A general strategy for highly efficient nanoparticle dispersing agents based on hybrid dendritic linear block copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2009Robert Vestberg Abstract A modular approach to the synthesis of a library of hybrid dendritic-linear copolymers was developed based on RAFT polymerization from monodisperse dendritic macroRAFT agents. By accurately controlling the molecular weight of the linear block, generation number of the dendrimer and the nature of the dendritic chains ends, the performance of these hybrid block copolymers as dispersing agents was optimized for a range of nanoparticles. For titanium dioxide nanoparticles, dispersion in a poly(methyl methacrylate) matrix was maximized with a second generation dendrimer containing four carboxylic acid end groups, and the quality of dispersion was observed to be superior to commercial dispersing agents for TiO2. This approach also allowed novel hybrid dendritic-linear dispersing agents to be prepared for the dispersion of Au and CdSe nanoparticles based on disulphide and phosphine oxide end groups, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1237,1258, 2009 [source] Poly(ethylene glycol)-based amphiphilic model conetworks: Synthesis by RAFT polymerization and characterizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2008Mariliz Achilleos Abstract Poly(ethylene glycol) (PEG)-containing quasi-model amphiphilic polymer conetworks (APCNs) were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization using ,,,-bis(2-cyanoprop-2-yl dithiobenzoate)-PEG as a bifunctional RAFT macrochain transfer agent (macro-CTA) and stepwise additions of a hydrophobic monomer and a crosslinker (crosslinker: macro-CTA = 10:1, reaction time 24 h). Three different types of monomers, methyl methacrylate (MMA), n -butyl acrylate and styrene, were employed as the hydrophobic monomers, whereas ethylene glycol dimethacrylate, ethylene glycol diacrylate and 1,4-divinylbenzene served as the respective crosslinkers. PEG homopolymer hydrophilic quasi-model networks were also prepared by RAFT-polymerizing the three crosslinkers directly onto the two active ends of the PEG-based macro-CTA. From the three ABA triblock copolymers prepared, the MMA-containing one was obtained at the highest polymerization yields. The crosslinking yields of the three ABA triblock copolymers with the corresponding crosslinkers were higher than those of the PEG-based macro-CTA with the same crosslinkers. The degrees of swelling (DSs) of all conetworks were measured in water and in tetrahydrofuran (THF). The DSs of the APCNs in THF were higher than those in water, whereas the reverse was true for the DSs of the hydrophilic homopolymer networks. Finally, the aqueous DSs of the APCNs were lower than those of the corresponding hydrophilic homopolymer networks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7556,7565, 2008 [source] Synthesis of well-defined polymeric activated estersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2008Patrick Theato Abstract Monomers bearing an activated ester group can be polymerized under various controlled polymerization techniques, such as ATRP, NMP, RAFT polymerization, or ROMP. Combining the functionalization of polymers via polymeric activated esters with these controlled polymerization techniques generate possibilities to realize highly functionalized polymer architectures. Within this highlight two different research areas of activated esters in polymer science will be discussed: (i) the preparation of defined reactive polymer architectures by controlled polymerization techniques and (ii) the preparation of defined reactive thin films. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6677,6687, 2008 [source] A strategy for synthesis of ion-bonded amphiphilic miktoarm star copolymers via supramolecular macro-RAFT agentJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2008Dairen Lu Abstract Amphiphilic supramolecular miktoarm star copolymers linked by ionic bonds with controlled molecular weight and low polydispersity have been successfully synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using an ion-bonded macromolecular RAFT agent (macro-RAFT agent). Firstly, a new tetrafunctional initiator, dimethyl 4,6-bis(bromomethyl)-isophthalate, was synthesized and used as an initiator for atom transfer radical polymerization (ATRP) of styrene to form polystyrene (PSt) containing two ester groups at the middle of polymer chain. Then, the ester groups were converted into tertiary amino groups and the ion-bonded supramolecular macro-RAFT agent was obtained through the interaction between the tertiary amino group and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP). Finally, ion-bonded amphiphilic miktoarm star copolymer, (PSt)2 -poly(N -isopropyl-acrylamide)2, was prepared by RAFT polymerization of N -isopropylacrylamide (NIPAM) in the presence of the supramolecular macro-RAFT agent. The polymerization kinetics was investigated and the molecular weight and the architecture of the resulting star polymers were characterized by means of 1H-NMR, FTIR, and GPC techniques. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5805,5815, 2008 [source] Synthesis of azobenzene-containing polymers via RAFT polymerization and investigation on intense fluorescence from aggregates of azobenzene-containing amphiphilic diblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Jie Xu Abstract The well-defined azobenzene-containing homopolymers, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)} (PAHMA), were synthesized via reversible addition fragmentation chain transfer polymerization (RAFT) in anisole solution using 2-cyanoprop-2-yl 1-dithionaphthalate (CPDN) as the RAFT agent and 2,2,-azobisisobutyronitrile (AIBN) as the initiator. The first-order kinetic plot of the polymerization and the linear dependence of molecular weights of the homopolymers with the relatively low polydispersity index values (PDIs , 1.25) on the monomer conversions were observed. Furthermore, the amphiphilic diblock copolymer, poly{6-(4-phenylazophenoxy)hexyl methacrylate (AHMA)}- b -poly{2-(dimethylamino)ethyl methacrylate (DMAEMA)} (PAHMA- b -PDMAEMA), was prepared with the obtained PAHMA as the macro-RAFT agent. The structures and properties of the polymers were characterized by 1H NMR and GPC, respectively. Interestingly, the amphiphilic diblock copolymers in chloroform (CHCl3) solution (PAHMA23 - b -PDMAEMA97 (4 × 10,5 M, Mn(GPC) = 18,400 g/mol, PDI = 1.48) and PAHMA28 - b -PDMAEMA117 (6 × 10,5 M, Mn(GPC) = 19,300 g/mol, PDI = 1.51) exhibited the intense fluorescence emission at ambient temperature. Moreover, the fluorescent intensity of PAHMA- b -PDMAEMA in CHCl3 was sensitive to the ultraviolet irradiation at 365 nm, which increased within the first 10 min and later decreased when irradiation time was prolonged to 30 min or longer. The well distributed, self-assembled micelles composed of azobenzene-containing amphiphilic diblock copolymers, (PAHMA- b -QPDMAEMA)s (QPDMAEMA is quaternized PDMAEMA), in the mixed N,N -dimethyl formamide (DMF)/H2O solutions were prepared. Their fluorescent intensities decreased with the increasing amount of water. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5652,5662, 2008 [source] Functionalization of multiwalled carbon nanotube via surface reversible addition fragmentation chain transfer polymerization and as lubricant additivesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008Xiaowei Pei Abstract Polymer-grafted multiwalled carbon nanotube (MWCNT) hybrid composite which possess a hard backbone of MWCNT and a soft shell of brush-like polystyrene (PSt) were synthesized. The reversible addition fragmentation chain transfer (RAFT) agents were successfully immobilized onto the surface of MWCNT first, and PSt chains were subsequently grafted from sidewall of MWCNT via RAFT polymerization. Chemical structure of resulting product and the quantities of grafted polymer were determined by Fourier transform infrared, thermal gravimetric analysis, nuclear magnetic resonance, and X-ray photoelectron spectra. Transmission electron microscopy and field emission scanning electron microscopy images clearly indicate that the nanotubes were coated with a polymer layer. Furthermore, the functionalized MWCNT as additives was added to base lubricant and the tribological property of resultant MWCNT lubricant was investigated with four-ball machines. The results indicate that the functionalization led to an improvement in the dispersion of MWCNT and as additives it amended the tribological property of base lubricant. The mechanism of the significant improvements on the tribological properties of the functionalized MWCNT as additives was discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3014,3023, 2008 [source] Synthesis of dithiocarbamate bearing azobenzene group and use for RAFT polymerization of vinyl monomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2007Xiaoming Wan Abstract A novel dithiocarbamate bearing azobenzene group, 2-(phenylazo-phenoxy-carbonyl) prop-2-yl 9H-carbazole-9-carbodithioate (APCDT), was synthesized and used as a RAFT agent in the polymerization of methyl methacrylate (MMA). The results showed that the controllability to the polymerization of MMA was promoted with APCDT as RAFT agent compared to 2-(ethoxycarbonyl) prop-2-yl 9H-carbazole-9-carbodithioate (EPCDT) under the same experimental conditions. The reason was attributed to the higher chain transfer constant of APCDT than that of EPCDT in the presence of more bulkier and more electrophilic azobenzene moiety. In addition, the RAFT polymerizations of St and methylacrylate (MA) using APCDT as the RAFT agent were also carried out. The ultraviolet spectrum and fluorescence spectrum of the obtained polymers were investigated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2886,2896, 2007 [source] RAFT polymerization of styrenic-based phosphonium monomers and a new family of well-defined statistical and block polyampholytesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2007Ran Wang Abstract We describe herein the first example of the controlled reversible addition-fragmentation chain transfer (RAFT) radical homo- and copolymerization of phosphonium-based styrenic monomers mediated with a trithiocarbonate-based RAFT chain transfer agent (CTA) directly in aqueous media. In the case of homopolymer syntheses the polymerizations proceed in a controlled fashion yielding materials with predetermined molecular characteristics as evidenced from the narrow molecular mass distributions (MMD) and the excellent agreement between the theoretical and experimentally determined molecular masses (MM). We also demonstrate the controlled nature of the homopolymerization of 4-vinylbenzoic acid with the same CTA in DMSO. We subsequently prepared both statistical and block copolymers from the phosphonium/4-vinylbenzoic acid monomers to yield the first examples of polyampholytes in which the cationic functional group is a quaternary phosphonium species. We show that the kinetic characteristics of the statistical copolymerizations are different from the homopolymerizations and proceed, generally, at a significantly faster rate although there appears to be a composition dependence on the rate. Given the inherent problems in characterizing such polyampholytic copolymers via aqueous size exclusion chromatography we have qualitatively proved their successful formation via FTIR spectroscopy. Finally, in a preliminary experiment we qualitatively demonstrate the ability of such pH-responsive block copolymers to undergo supramolecular self-assembly. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2468,2483, 2007 [source] Functionalized multi-walled carbon nanotubes with poly(N -(2-hydroxypropyl)methacrylamide) by RAFT polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006Chun-Yan Hong Abstract In this study, we grafted water-soluble biocompatible polymer, poly(N -(2-hydroxypropyl)methacrylamide) (PHPMA), onto the surface of multi-walled carbon nanotubes (MWNTs). The reversible addition-fragmentation chain transfer (RAFT) agents, dithioesters, were successfully immobilized onto the surface of MWNTs first, PHPMA chains were then subsequently grafted onto MWNTs via RAFT polymerization by using dithioesters immobilized on MWNTs as RAFT agent. FTIR, XPS, 1H NMR, Raman and TGA were used to characterize the resulting products and to determine the content of water-soluble PHPMA chains in the product. The MWNTs grafted with PHPMA chains have good solubility in distilled water, PBS buffer, and methanol. TEM images of the samples provide direct evidence for the formation of a nanostructure that MWNTs coated with polymer layer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2419,2427, 2006 [source] Synthesis and characterizations of well-defined branched polymers with AB2 branches by combination of RAFT polymerization and ROP as well as ATRPJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Bin Luan Abstract A well-defined branched copolymer with PLLA- b -PS2 branches was prepared by combination of reversible addition-fragmentation transfer (RAFT) polymerization, ring-opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA- co -HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA- co -HEA)- g -PLLAOH with divergent agent, the macro initiator, poly(MA- co -HEA)- g -PLLABr2 was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA- co -HEA)- g -(PLLA- b -PS2). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their 1H NMR and GPC measurements. DSC results show one T = 3 °C for the poly(MA- co -HEA), T = ,5 °C, T= 122 °C, and T = 157 °C for the branched copolymers (poly(MA- co -HEA)- g -PLLA), and T = 51 °C, T = 116 °C, and T = 162 °C for poly(MA- co -HEA)- g -(PLLA- b -PS2). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 549,560, 2006 [source] Dendrimer-star polymer and block copolymer prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization with dendritic chain transfer agentJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2005Chun-Yan Hong Abstract 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 [source] Synthesis of Well-Defined Statistical and Diblock Copolymers of Acrylamide and Acrylic Acid by Inverse Miniemulsion Raft PolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2010Liu Ouyang Abstract Well-defined statistical and diblock copolymers with acrylamide and acrylic acid were synthesized by inverse miniemulsion RAFT polymerization. Statistical copolymers with various composition ratios were synthesized. Compositional drift was observed during polymerization. Acrylamide was polymerized with a water-soluble initiator (VA-044) at 60,°C to give the RAFT-agent-containing acrylamide homopolymer with a narrow molecular-weight distribution (PDI,<,1.3), which was then chain-extended with acrylic acid to obtain the diblock copolymer. [source] Structures and Chiroptical Properties of Thermoresponsive Block Copolymers Containing L -Proline MoietiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2007Hideharu Mori Abstract Amino acid-based block copolymers containing poly(A-Pro-OMe) have been synthesized by RAFT polymerization using the dithioester-terminated poly(DMA) as a macro-CTA. An amphiphilic block copolymer composed of polystyrene as a hydrophobic segment and poly(A-Pro-OMe) as a hydrophilic segment was also prepared using polystyrene as the macro-CTA. The chiroptical properties of the block copolymer, poly(DMA)- block -poly(A-Pro-OMe), was evaluated by specific rotation, CD, and UV-vis spectroscopy. The assembled structure of the block copolymer on a mica surface was characterized by SFM. Thermally induced phase separations of the random and block copolymers were also studied in aqueous solution. [source] A Novel Strategy to Synthesize Double Comb-Shaped Water Soluble Copolymer by RAFT PolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006De-Hui Han Abstract Summary: A double comb-shaped water soluble copolymer, poly[poly(ethylene oxide) methyl ether methacrylate]- block -poly(N -isopropylacrylamide)- block -poly[poly (ethylene oxide) methyl ether methacrylate], abbreviated as [P(MA-MPEO)- block -PNIPAM- block -P(MA-MPEO)], with a controlled molecular weight and narrow polydispersity was successively synthesized using a macromonomer technique. The 60Co , irradiation polymerization of MA-MPEO in the presence of dibenzyl trithiocarbonate (DBTTC) at room temperature afforded a polymer, P(MA-MPEO)-SC(S)S-P(MA-MPEO), which was subsequently used as a macro RAFT agent in the RAFT polymerization of N -isopropylacrylamide, and water soluble double comb-shaped copolymers, P(MA-MPEO)- block -PNIPAM- block -P(MA-MPEO), were successfully obtained. Structure of the double comb-shaped copolymer. [source] One-Pot Synthesis of Micelles with a Cross-Linked Poly(acrylic acid) CoreMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2006Genhua Zheng Abstract Summary: Stable micelles with polystyrene (PS) as a shell and cross-linked poly[(acrylic acid)- co -(ethylene glycol diacrylate)] as a core have been successfully prepared by reversible addition fragmentation chain transfer (RAFT) copolymerization of acrylic acid and ethylene glycol diacrylate in a selective solvent with PS-SC(S)Ph as a RAFT agent. For the preparation of stable micelles, the RAFT polymerizations are carried out in different solvents: benzene, cyclohexane, and mixtures of tetrahydrofuran and cyclohexane. The monomer/PS-SC(S)Ph molar ratio and molecular weight of the macro-RAFT agent, PS-SC(S)Ph, influence the RAFT polymerization and the formation of micelles. Block copolymerization in selective solvent with the RAFT agent. [source] Gold Nanoparticles Functionalized by a Dextran-Based pH- and Temperature-Sensitive PolymerMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010Weipeng Lv Abstract A dextran-based dual-sensitive polymer is employed to endow gold nanoparticles with stability and pH- and temperature-sensitivity. The dual-sensitive polymer is prepared by RAFT polymerization of N -isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder-form. UV and DLS measurements confirm that the temperature-induced optical changes and aggregation behaviors of the particles are strongly dependent on pH. [source] A Strategy for Synthesis of Ion-Bonded Supramolecular Star Polymers by Reversible Addition-Fragmentation Chain Transfer (RAFT) PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2008Kang Tao Abstract We have developed a novel strategy for the preparation of ion-bonded supramolecular star polymers by RAFT polymerization. An ion-bonded star supramolecule with six functional groups was prepared from a triphenylene derivative containing tertiary amino groups and trithiocarbonate carboxylic acid, and used as the RAFT agent in polymerizations of tert -butyl acrylate (tBA) and styrene (St). Molecular weights and structures of the polymers were characterized by 1H NMR and GPC. The results show that the polymerization possesses the character of living free-radical polymerization and the ion-bonded supramolecular star polymers PSt, PtBA, and PSt- b -PtBA, with six well-defined arms, were successfully synthesized. [source] Experimental Requirements for an Efficient Control of Free-Radical Polymerizations via the Reversible Addition-Fragmentation Chain Transfer (RAFT) Process,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2006Arnaud Favier Abstract Summary: Reversible addition-fragmentation chain transfer (RAFT) polymerization is a recent and very versatile controlled radical polymerization technique that has enabled the synthesis of a wide range of macromolecules with well-defined structures, compositions, and functionalities. The RAFT process is based on a reversible addition-fragmentation reaction mediated by thiocarbonylthio compounds used as chain transfer agents (CTAs). A great variety of CTAs have been designed and synthesized so far with different kinds of substituents. In this review, all of the CTAs encountered in the literature from 1998 to date are reported and classified according to several criteria : i) the structure of their substituents, ii) the various monomers that they have been polymerized with, and iii) the type of polymerization that has been performed (solution, dispersed media, surface initiated, and copolymerization). Moreover, the influence of various parameters is discussed, especially the CTA structure relative to the monomer and the experimental conditions (temperature, pressure, initiation, CTA/initiator ratio, concentration), in order to optimise the kinetics and the efficiency of the molecular-weight-distribution control. Schematic of the RAFT polymerization. [source] | |||||||||||||