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Monomer Conversion (monomer + conversion)
Selected AbstractsTerpolymerization monitoring with ATR-FTIR spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2001Hong Hua Abstract Butyl acrylate, methyl methacrylate, and vinyl acetate solution and emulsion terpolymerizations were conducted. Attenuated total relflection-Fourier transform infrared spectroscopy equipped with conduit and diamond-composite sensor technology was used to monitor solution terpolymerizations off-line and emulsion terpolymerizations in-line. Monomer conversion and terpolymer composition changes as a function of time were calculated by monitoring the peak height of characteristic absorbances of each monomer. Results obtained from the ReactIRÔ 1000 reaction-analysis system agreed well with those determined by traditional gravimetry and 1H NMR spectroscopy. For the solution terpolymerizations, improved models developed previously to incorporate solvent effects on solution polymerizations of butyl acrylate and vinyl acetate monomers were applied to predict monomer conversion, copolymer composition, and molecular weight averages. Comparisons between experimental data and model predictions are presented. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1860,1876, 2001 [source] Single-Mode Microwave Ovens as New Reaction Devices: Accelerating the Living Polymerization of 2-Ethyl-2-OxazolineMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Frank Wiesbrock Abstract Summary: The ring-opening cationic polymerization of 2-ethyl-2-oxazoline was performed in a single-mode microwave reactor as the first example of a microwave-assisted living polymerization. The observed increase in reaction rates by a factor of 350 (6 h,,,1 min) in the range from 80 to 190,°C could be attributed solely to a temperature effect as was clearly shown by control experiments and the determined activation energy. Because of the homogenous microwave irradiation, the polymerization could be performed in bulk or with drastically reduced solvent ratios (green chemistry). Monomer conversion, represented by the ratio ln{[M0]/[Mt]}, plotted against time for six temperatures in the range from 80 to 180,°C, and polymerization reaction vials, showing an increase in yellow color for those reactions performed (well) above and below 140,°C, indicating side reactions. [source] Biodegradable poly(vinyl alcohol)- graft - poly(,-caprolactone) comb-like polyester: Microwave synthesis and its characterizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Zhaoju Yu Abstract Poly(vinyl alcohol)-initiated microwave-assisted ring opening polymerization of ,-caprolactone in bulk was investigated, and a series of poly(vinyl alcohol)- graft -poly(,-caprolactone) (PVA- g -PCL) copolymers were prepared, with the degree of polymerization (DP) of PCL side chains and the degree of substitution (DS) of PVA by PCL being in the range of 3,24 and 0.35,0.89, respectively. The resultant comb-like PVA- g -PCL copolymers were confirmed by means of FTIR, 1H NMR, and viscometry measurement. The introduction of hydrophilic backbone resulted in the decrease in both melting point and crystallization property of the PVA- g -PCL copolymers comparing with linear PCL. With higher microwave power, the DP of PCL side chains and DS of PVA backbone were higher, and the polymerization reaction proceeded more rapidly. Both the DP and monomer conversion increased with irradiation time, while the DS increased first and then remained constant. With initiator in low concentration, the DP and DS were higher, while the monomer was converted more slowly. Microwaves dramatically improved the polymerization reaction in comparison of conventional heating method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3973,3979, 2007 [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] Room-temperature RAFT copolymerization of 2-chloroallyl azide with methyl acrylate and versatile applications of the azide copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2010Guang Li Abstract A new vinyl azide monomer, 2-chlorallyl azide (CAA), has been synthesized from commercially available reagent in one step. The reversible addition fragmentation chain transfer (RAFT) copolymerization of CAA with methyl acrylate (MA) was carried out at room temperature using a redox initiator, benzoyl peroxide (BPO)/N,N -dimethylaniline (DMA), in the presence of benzyl 1H -imidazole-1-carbodithioate (BICDT). The polymerization results showed that the process bears the characteristics of controlled/living radical polymerizations, such as the molecular weight increasing linearly with the monomer conversion, the molecular weight distribution being narrow, and a linear relationship existing between ln([M]0/[M]) and the polymerization time. Chain extension polymerization was performed successfully to prepare block copolymer. Furthermore, the azide copolymers were functionalized by CuI -catalyzed "click" reaction with alkyne-containing poly(ethylene glycol) (PEG) to yield graft copolymers with hydrophilic PEG side chains. Surface modification of the glass sheet was successfully achieved via the crosslinking reaction of the azide copolymer under UV irradiation at ambient temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1348,1356, 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 and kinetic analysis of DPE controlled radical polymerization of MMAJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009Ying-Da Luo Abstract The 1,1-diphenylethene (DPE) controlled radical polymerization of methyl methacrylate was performed at 80 °C by using AIBN as an initiator and DPE as a control agent. It was found that the molecular weight of polymer remained constant with monomer conversion throughout the polymerization regardless of the amounts of DPE and initiator in formulation. To understand the result of constant molecular weight of living polymers in DPE controlled radical polymerization, a living kinetic model was established in this research to evaluate all the rate constants involved in the DPE mechanism. The rate constant k2, corresponding to the reactivation reaction of the DPE capped dormant chains, was found to be very small at 80 °C (1 × 10,5 s,1), that accounted for the result of constant molecular weight of polymers throughout the polymerization, analogous to a traditional free radical polymerization system that polymer chains were terminated by chain transfer. The polydispersity index (PDI) of living polymers was well controlled <1.5. The low PDI of obtained living polymers was due to the fact that the rate of growing chains capped by DPE was comparable with the rate of propagation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source] Branched polystyrene with abundant pendant vinyl functional groups from asymmetric divinyl monomerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Zhong-Min Dong Abstract Branched polystyrenes with abundant pendant vinyl functional groups were prepared via radical polymerization of an asymmetric divinyl monomer, which possesses a higher reactive styryl and a lower reactive butenyl. Employing a fast reversible addition fragmentation chain transfer (RAFT) equilibrium, the concentration of active propagation chains remained at a low value and thus crosslinking did not occur until a high level of monomer conversion. The combination of a higher reaction temperature (120 °C) and RAFT agent cumyl dithiobenzoate was demonstrated to be optimal for providing both a more highly branched architecture and a higher polymer yield. The molecular weights (Mws) increased with monomer conversions because of the controlled radical polymerization characteristic, whereas the Mw distributions broadened showing a result of the gradual increase of the degree of branching. The evolution of branched structure has been confirmed by a triple detection size exclusion chromatography (TRI-SEC) and NMR technique. Furthermore, the double bonds in the side chains were successfully used for chemical modification reactions. 1H NMR and FTIR measurements reveal that the great mass of pendant vinyl groups were converted to the corresponding objective end-groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6023,6034, 2008 [source] Living cationic polymerization of amide-functional vinyl ethers: Specific properties of SnCl4 -based initiating systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2008Motomasa Yonezumi Abstract Living cationic copolymerization of amide-functional vinyl ethers with isobutyl vinyl ether (IBVE) was achieved using SnCl4 in the presence of ethyl acetate at 0 °C: the number,average molecular weight of the obtained polymers increased in direct proportion to the monomer conversion with relatively low polydispersity, and the amide-functional monomer units were introduced almost quantitatively. To optimize the reaction conditions, cationic polymerization of IBVE in the presence of amide compounds, as a model reaction, was also examined using various Lewis acids in dichloromethane. The combination of SnCl4 and ethyl acetate induced living cationic polymerization of IBVE at 0 °C when an amide compound, whose nitrogen is adjacent to a phenyl group, was used. The versatile performance of SnCl4 especially for achieving living cationic polymerization of various polar functional monomers was demonstrated in this study as well as in our previous studies. Thus, the specific properties of the SnCl4 initiating system are discussed by comparing with the EtxAlCl3,x systems from viewpoints of hard and soft acids and bases principle and computational chemistry. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6129,6141, 2008 [source] Controlled cationic polymerization of cyclopentadiene with B(C6F5)3 as a coinitiator in the presence of waterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2008Sergei V. Kostjuk Abstract The controlled cationic polymerization of cyclopentadiene (CPD) at 20 °C using 1-(4-methoxyphenyl)ethanol (1)/B(C6F5)3 initiating system in the presence of fairly large amount of water is reported. The number,average molecular weights of the obtained polymers increased in direct proportion to monomer conversion in agreement with calculated values and were inversely proportional to initiator concentration, while the molecular weight distribution slightly broadened during the polymerization (Mw/Mn , 1.15,1.60). 1H NMR analyses confirmed that the polymerization proceeds via reversible activation of the COH bond derived from the initiator to generate the growing cationic species, although some loss of hydroxyl functionality happened in the course of the polymerization. It was also shown that the enchainment in cationic polymerization of CPD was affected by the nature of the solvent(s): for instance, polymers with high regioselectivity ([1,4] up to 70%) were obtained in acetonitrile, whereas lower values (around 60%) were found in CH2Cl2/CH3CN mixtures. Aqueous suspension polymerization of CPD using the same initiating system was successfully performed and allowed to synthesize primarily hydroxyl-terminated oligomers (Fn = 0.8,0.9) with Mn , 1000 g mol,1 and broad MWD (Mw/Mn , 2.2). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4734,4747, 2008 [source] Living cationic polymerization of 2-adamantyl vinyl etherJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 5 2008Tamotsu Hashimoto Abstract Living cationic polymerization of 2-adamantyl vinyl ether (2-vinyloxytricyclo[3.3.1.1]3,7decane; 2-AdVE) was achieved with the CH3CH(OiBu)OCOCH3/ethylaluminum sesquichloride/ethyl acetate [CH3CH(OiBu)OCOCH3/Et1.5AlCl1.5/CH3COOEt] initiating system in toluene at 0 °C. The number-average molecular weights (Mn's) of the obtained poly(2-AdVE)s increased in direct proportion to monomer conversion and produced the polymers with narrow molecular weight distributions (MWDs) (Mw/Mn = ,1.1). When a second monomer feed was added to the almost polymerized reaction mixture, the added monomer was completely consumed and the Mn's of the polymers showed a direct increase against conversion of the added monomer. Block and statistical copolymerization of 2-AdVE with n -butyl vinyl ether (CH2CHOCH2 CH2CH2CH3; NBVE) were possible via living process based on the same initiating system to give the corresponding copolymers with narrow MWDs. Grass transition temperature (Tg) and thermal decomposition temperature (Td) of the poly(2-AdVE) (e.g., Mn = 22,000, Mw/Mn = 1.17) were 178 and 323 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1629,1637, 2008 [source] Synthesis of poly(4-vinylpyridine) by reverse atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2007Gregory T. Lewis Abstract Controlled radical polymerization of 4-vinylpyridine (4VP) was achieved in a 50 vol % 1-methyl-2-pyrrolidone/water solvent mixture using a 2,2,-azobis(2,4-dimethylpentanitrile) initiator and a CuCl2/2,2,-bipyridine catalyst,ligand complex, for an initial monomer concentration of [M]0 = 2.32,3.24 M and a temperature range of 70,80 °C. Radical polymerization control was achieved at catalyst to initiator molar ratios in the range of 1.3:1 to 1.6:1. First-order kinetics of the rate of polymerization (with respect to the monomer), linear increase of the number,average degree of polymerization with monomer conversion, and a polydispersity index in the range of 1.29,1.35 were indicative of controlled radical polymerization. The highest number,average degree of polymerization of 247 (number,average molecular weight = 26,000 g/mol) was achieved at a temperature of 70 °C, [M]0 = 3.24 M and a catalyst to initiator molar ratio of 1.6:1. Over the temperature range studied (70,80 °C), the initiator efficiency increased from 50 to 64% whereas the apparent polymerization rate constant increased by about 60%. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5748,5758, 2007 [source] Homogeneous phase polymerization of vinylidene fluoride in supercritical carbon dioxideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2007Sabine Beuermann Abstract For the first time, stabilizer-free vinylidene fluoride (VDF) homopolymerizations were carried out in homogenous phase with supercritical CO2 using the conventional initiator di- tert butyl peroxide (DTBP). In-line FT-NIR spectroscopy showed that complete monomer conversion may be obtained. Molecular weights were determined via size-exclusion chromatography and polymer endgroup analysis by 1H-NMR spectroscopy. The number average molecular weights were below 104 g mol,1 and polydispersities ranged from 3.1 to 5.7 depending on DTBP and VDF concentration. For allowing isothermal reaction, high CO2 contents ranging from 61 to 83 wt % were used. The high-temperature and high-pressure conditions required for homogeneous polymerization did not alter the amount of defects in VDF chaining. Scanning electron microscopy indicated that regular stack-type particles are obtained upon expansion of the homogeneous polymerization mixture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5626,5635, 2007 [source] Diblock copolymers based on allyl methacrylate: Synthesis, characterization, and chemical modificationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007Rodrigo París Abstract Different diblock copolymers constituted by one segment of a monomer supporting a reactive functional group, like allyl methacrylate (AMA), were synthesized by atom transfer radical polymerization (ATRP). Bromo-terminated polymers, like polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(butyl acrylate) (PBA) were employed as macroinitiators to form the other blocks. Copolymerizations were carried out using copper chloride with N,N,N,,N,,N, -pentamethyldiethylenetriamine (PMDETA) as the catalyst system in benzonitrile solution at 70 °C. At the early stage, the ATRP copolymerizations yielded well-defined linear block copolymers. However, with the polymerization progress a change in the macromolecular architecture takes place due to the secondary reactions caused by the allylic groups, passing to a branched and/or star-shaped structure until finally yielding gel at monomer conversion around 40% or higher. The block copolymers were characterized by means of size exclusion chromatography (SEC), 1H NMR spectroscopy, and differential scanning calorimetry (DSC). In addition, one of these copolymers, specifically P(BA- b -AMA), was satisfactorily modified through osmylation reaction to obtain the subsequent amphiphilic diblock copolymer of P(BA- b -DHPMA), where DHPMA is 2,3-dihydroxypropyl methacrylate; demonstrating the feasibility of side-chain modification of the functional obtained copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3538,3549, 2007 [source] Polymerization of ,-pinene with Schiff-base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(,-pinene) at high temperature with high productivityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007Peng Yu Abstract A series of easily accessible and stable Schiff-base nickel complexes (complex 1,4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight ,-pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of ,-pinene (Mn , 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 107 g poly,-pinene/mol of Ni. 1H NMR analyses showed that the obtained ,-pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff-base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739,3746, 2007 [source] Living carbocationic copolymerization of isobutylene with styreneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2007Judit E. Puskas Abstract The carbocationic copolymerization of isobutylene (IB) and styrene (St), initiated by 2-chloro-2,4,4-trimethylpentane/TiCl4 in 60/40 (v/v) methyl chloride/hexane at ,90 °C, was investigated. At a low total concentration (0.5 mol/L), slow initiation and rapid monomer conversion were observed. At a high total comonomer concentration (3 mol/L), living conditions (a linear semilogarithmic rate and Mn,conversion plots) were found, provided that the St concentration was above a critical value ([St]0 , 0.6 mol/L). The breadth of the molecular weight distribution decreased with increasing IB concentration in the feed, reaching Mw/Mn , 1.1. St homopolymerization was also living at a high total concentration, yielding polystyrene with Mn = 82,000 g/mol, the highest molecular weight ever achieved in carbocationic St polymerization. An analysis of this system by both the traditional gravimetric,NMR copolymer composition method and FTIR demonstrated penultimate effects. IB enrichment was found in the copolymers at all feed compositions, with very little drift at a high total concentration and above the critical St concentration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1778,1787, 2007 [source] Synthesis and properties of the polythiourethanes obtained by the cationic ring-opening polymerization of cyclic thiourethanesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2006Daisuke Nagai Abstract The cationic ring-opening polymerization of a five-membered thiourethane [3-benzyl-1,3-oxazolidine-2-thione (BOT)] with boron trifluoride etherate afforded the corresponding polythiourethane with a narrow molecular weight distribution in an excellent yield. The molecular weight of the polymers could be controlled by the feed ratio of the monomer to the initiator. A kinetic study of the polymerization revealed that the polymerization rate of BOT (1.3 × 10,2 L mol,1 min,1) was two times larger than that of the six-membered thiourethane [3-benzyltetrahydro-1,3-oxazolidine-2-thione (BTOT); 6.8 × 10,3 L mol,1 min,1], and the monomer conversion obeyed the first-order kinetic equation. These observations, along with the successful results in the two-stage polymerization, supported the idea that this polymerization proceeded in a controlled manner. Block copolymerizations of BOT with BTOT were also carried out to afford the corresponding di- and triblock copolymers with narrow molecular weight distributions. The order of the 5% weight loss temperatures was as follows: poly(3-benzyltetrahydro-1,3-oxazolidine-2-thione) [poly(BTOT)] > poly(BTOT54 - b -BOT46) > poly(3-benzyl-1,3-oxazolidine-2-thione) [poly(BOT)]. This indicated that an increase in the BTOT unit content raised the decomposition temperature. The order of the refractive indices was poly(BOT) > poly(BTOT54 - b -BOT46) > poly(BTOT54 - b -BOT46 - b -BTOT50) > poly(BTOT); this was in accord with the order of the sulfur content in the polymer chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4795,4803, 2006 [source] Homopolymerization of cyclic esters initiated by lanthanide isopropoxides supported by 2,2,-ethylene-bis(4,6-di- tert -butylphenolate) ligandsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2006Xiaoping Xu Abstract Lanthanide isopropoxides supported by carbon-bridged bisphenolate ligands of 2,2,-ethylene-bis(4,6-di- tert -butylphenoxo) {[(EDBP)Ln(,-OPri)(THF)2]2, where Ln is Nd (1), Sm (2), or Yb (3) and THF is tetrahydrofuran} were synthesized by protic exchange reactions in high yields with Cp3Ln compounds as raw materials, and complex 1 was structurally characterized. Complexes 1,3 were shown to be efficient initiators for the ring-opening polymerization of ,-caprolactone (,-CL) and 2,2-dimethyltrimethylene carbonate (DTC). Complexes 1,3 could initiate the controlled polymerization of ,-CL, and the polymerization rate was first-order with respect to the monomer. The influence of the reaction conditions on the monomer conversion, molecular weight, and molecular weight distribution of the resultant polymers was investigated. End-group analyses of the oligomers of ,-CL and DTC showed that the polymerization underwent a coordination,insertion mechanism. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4409,4419, 2006 [source] Controlled radical polymerization of a trialkylsilyl methacrylate by reversible addition,fragmentation chain transfer polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2005M. N. Nguyen Abstract The reversible addition,fragmentation chain transfer (RAFT) polymerization of a hydrolyzable monomer (tert -butyldimethylsilyl methacrylate) with cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate as chain-transfer agents was studied in toluene solutions at 70 °C. The resulting homopolymers had low polydispersity (polydispersity index < 1.3) up to 96% monomer conversion with molecular weights at high conversions close to the theoretical prediction. The profiles of the number-average molecular weight versus the conversion revealed controlled polymerization features with chain-transfer constants expected between 1.0 and 10. A series of poly(tert -butyldimethylsilyl methacrylate)s were synthesized over the molecular weight range of 1.0 × 104 to 3.0 × 104, as determined by size exclusion chromatography. As strong differences of hydrodynamic volumes in tetrahydrofuran between poly(methyl methacrylate), polystyrene standards, and poly(tert -butyldimethylsilyl methacrylate) were observed, true molecular weights were obtained from a light scattering detector equipped in a triple-detector size exclusion chromatograph. The Mark,Houwink,Sakurada parameters for poly(tert -butyldimethylsilyl methacrylate) were assessed to obtain directly true molecular weight values from size exclusion chromatography with universal calibration. In addition, a RAFT agent efficiency above 94% was confirmed at high conversions by both light scattering detection and 1H NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5680,5689, 2005 [source] In situ Fourier transform near infrared spectroscopy monitoring of copper mediated living radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2004Vincent Darcos Abstract In situ Fourier transform near infrared (FTNIR) spectroscopy was successfully used to monitor monomer conversion during copper mediated living radical polymerization with N -(n -propyl)-2-pyridylmethanimine as a ligand. The conversion of vinyl protons in methacrylic monomers (methyl methacrylate, butyl methacrylate, and N -hydroxysuccinimide methacrylate) to methylene protons in the polymer was monitored with an inert fiber-optic probe. The monitoring of a poly(butyl methacrylate- b -methyl methacrylate- b -butyl methacrylate) triblock copolymer has also been reported with difunctional poly(methyl methacrylate) as a macroinitiator. In all cases FTNIR results correlated excellently with those obtained by 1H NMR. On-line near infrared (NIR) measurement was found to be more accurate because it provided many more data points and avoided sampling during the polymerization reaction. It also allowed the determination of kinetic parameters with, for example, the calculation of an apparent first-order rate constant. All the results suggest that FTNIR spectroscopy is a valuable tool to assess kinetic data. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4933,4940, 2004 [source] Ring-opening polymerization and block copolymerization of L -lactide with divalent samarocene complexJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2003Dongmei Cui Abstract Divalent samarocene complex [(C5H9C5H4)2Sm(tetrahydrofuran)2] was prepared and characterized and used to catalyze the ring-opening polymerization of L -lactide (L-LA) and copolymerization of L-LA with caprolactone (CL). Several factors affecting monomer conversion and molecular weight of polymer, such as polymerization time, temperature, monomer/catalyst ratio, and solvent, were examined. The results indicated that polymerization was rapid, with monomer conversions reaching 100% within 1 h, and the conformation of L-LA was retained. The structure of the block copolymer of CL/L-LA was characterized by NMR and differential scanning calorimetry. The morphological changes during crystallization of poly(caprolactone) (PCL)- b -P(L-LA) copolymer were monitored with real-time hot-stage atomic force microscopy (AFM). The effect of temperature on the morphological change and crystallization behavior of PCL- b -P(L-LA) copolymer was demonstrated through AFM observation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2667,2675, 2003 [source] Modeling the reversible addition,fragmentation transfer polymerization processJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2003Aileen R. Wang Abstract A kinetic model has been developed for reversible addition,fragmentation transfer (RAFT) polymerization with the method of moments. The model predicts the monomer conversion, number-average molecular weight, and polydispersity of the molecular weight distribution. It also provides detailed information about the development of various types of chain species during polymerization, including propagating radical chains, adduct radical chains, dormant chains, and three types of dead chains. The effects of the RAFT agent concentration and the rate constants of the initiator decomposition, radical addition, fragmentation, disproportionation, and recombination termination of propagating radicals and cross-termination between propagating and adduct radicals on the kinetics and polymer chain properties are examined with the model. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1553,1566, 2003 [source] Fluorescent polymer particles by emulsion and miniemulsion polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2003Frédéric Tronc Abstract We describe the synthesis and characterization of latex particles labeled with a brightly fluorescent yellow dye (HY) based on the benzothioxanthene ring structure. Three dye derivatives were synthesized with different spacers connecting the HY nucleus to a methacrylate group. For one of the dyes (HY2CMA, rA), we show that the reactivity ratios with styrene (rA = 0.71, rB = 0.25) and butyl methacrylate (rA = 0.87, rB = 0.14) should lead to random dye incorporation if the amount of dye in the feed is small. Seeded emulsion polymerization fails to lead to significant dye incorporation unless large amounts of nonionic surfactant are present. In contrast, miniemulsion polymerization worked well to yield latex particles of polystyrene, poly(butyl methacrylate), and poly(methyl methacrylate) with high monomer conversion and essentially quantitative dye incorporation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 766,778, 2003 [source] Atom transfer radical polymerization of n -butyl acrylate catalyzed by CuBr/N -(n -hexyl)-2-pyridylmethanimineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Huiqi Zhang Abstract The homogeneous atom transfer radical polymerization (ATRP) of n -butyl acrylate with CuBr/N -(n -hexyl)-2-pyridylmethanimine as a catalyst and ethyl 2-bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different solvents such as toluene, anisole, N,N -dimethylformamide, and 1-butanol were linear throughout the reactions, and the experimental molecular weights increased linearly with increasing monomer conversion and were very close to the theoretical values. These, together with the relatively narrow molecular weight distributions (polydispersity index , 1.40 in most cases with monomer conversion > 50%), indicated that the polymerization was living and controlled. Toluene appeared to be the best solvent for the studied ATRP system in terms of the polymerization rate and molecular weight distribution among the solvents used. The polymerization showed zero order with respect to both the initiator and the catalyst, probably because of the presence of a self-regulation process at the beginning of the reaction. The reaction temperature had a positive effect on the polymerization rate, and the optimum reaction temperature was found to be 100 °C. An apparent enthalpy of activation of 81.2 kJ/mol was determined for the ATRP of n -butyl acrylate, corresponding to an enthalpy of equilibrium of 63.6 kJ/mol. An apparent enthalpy of activation of 52.8 kJ/mol was also obtained for the ATRP of methyl methacrylate under similar reaction conditions. Moreover, the CuBr/N -(n -hexyl)-2-pyridylmethanimine-based system was proven to be applicable to living block copolymerization and living random copolymerization of n -butyl acrylate with methyl methacrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3549,3561, 2002 [source] Controlled radical polymerization of 2-hydroxyethyl methacrylate with a hydrophilic ruthenium complex and the synthesis of amphiphilic random and block copolymers with methyl methacrylate,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2002Yusuke Fuji Abstract A hydrophilic ruthenium complex with ionic phosphine ligands {1: RuCl2[P(3-C6H4SO3Na)(C6H5)2]2} induced controlled radical polymerization of 2-hydroxyethyl methacrylate (HEMA) in methanol under homogeneous conditions; the initiator was a chloride (R-Cl) such as CHCl2COPh. The number-average molecular weights of poly(HEMA) increased in direct proportion to monomer conversion, and the molecular weight distributions were relatively narrow (Mw/Mn = 1.4,1.7). A similar living radical polymerization was possible with (MMA)2 -Cl [(CH3)2C(CO2CH3)CH2C(CH3)(CO2CH3)Cl] as an initiator coupled with amine additives such as n -Bu3N. In a similar homogeneous system in methanol, methyl methacrylate (MMA) could also be polymerized in living fashion with the R-Cl/1 initiating system. Especially for such hydrophobic polymers, the water-soluble ruthenium catalyst was readily removed from the polymers by simple washing with an aqueous dilute acid. This system can be applied to the direct synthesis of amphiphilic random and block copolymers of HEMA and MMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2055,2065, 2002 [source] Long-lived intermediates in reversible addition,fragmentation chain-transfer (RAFT) polymerization generated by , radiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2002Christopher Barner-Kowollik Abstract A novel experimental procedure is presented that allowed probing of reversible addition,fragmentation chain-transfer (RAFT) free-radical polymerizations for long-lived species. The new experimental sequence consisted of gamma irradiation of a mixture of initial RAFT agent (cumyl dithiobenzoate) and monomer at ambient temperature, a subsequent predetermined waiting period without initiation source also at ambient temperature, and then heating of the reaction mixture to a significantly higher temperature. After each sequence step, the monomer conversion and molecular weight distribution were determined, indicating that controlled polymer formation occurs only during the heating period. The results indicated that stable intermediates (either radical or nonradical in nature) are present in such experiments because thermal self-initiation of the monomer can be excluded as the reason for polymer formation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1058,1063, 2002 [source] Terpolymerization monitoring with ATR-FTIR spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2001Hong Hua Abstract Butyl acrylate, methyl methacrylate, and vinyl acetate solution and emulsion terpolymerizations were conducted. Attenuated total relflection-Fourier transform infrared spectroscopy equipped with conduit and diamond-composite sensor technology was used to monitor solution terpolymerizations off-line and emulsion terpolymerizations in-line. Monomer conversion and terpolymer composition changes as a function of time were calculated by monitoring the peak height of characteristic absorbances of each monomer. Results obtained from the ReactIRÔ 1000 reaction-analysis system agreed well with those determined by traditional gravimetry and 1H NMR spectroscopy. For the solution terpolymerizations, improved models developed previously to incorporate solvent effects on solution polymerizations of butyl acrylate and vinyl acetate monomers were applied to predict monomer conversion, copolymer composition, and molecular weight averages. Comparisons between experimental data and model predictions are presented. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1860,1876, 2001 [source] Preparation of Polystyrene/Clay Nanocomposites by Free-Radical Polymerization in DispersionMACROMOLECULAR MATERIALS & ENGINEERING, Issue 11 2009Nagi Greesh Abstract Fully exfoliated PS/clay nanocomposites were prepared via FRP in dispersion. Na-MMT clay was pre-modified using MPTMS before being used in a dispersion polymerization process. The objective of this study was to determine the impact of the clay concentrations on the monomer conversion, the polymer molecular weight, and the morphology and thermal stability of the nanocomposites prepared via dispersion polymerization. DLS and SEM revealed that the particle size decreased and became more uniformly distributed with increasing clay loading. XRD and TEM revealed that nanocomposites at low clay loading yielded exfoliated structures, while intercalated structures were obtained at higher clay loading. [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] Effects of Ionic Liquid [Me3NC2H4OH]+[ZnCl3], on , -Radiation Polymerization of Methyl Methacrylate in Ethanol and N,N -DimethylformamideMACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2005Guozhong Wu Abstract Summary: Radiation-induced polymerization of methyl methacrylate (MMA) in ethanol (EtOH) and N,N -dimethylformamide (DMF) in the presence of ionic liquid [Me3NC2H4OH]+[ZnCl3], is reported. A substantial increase in monomer conversion and molecular weight is observed at room-temperature ionic liquid (RTIL) >60 vol.-%, and the resulting PMMA has a broad multimodal MWD. A clear difference in the MWD pattern is noted between EtOH/RTIL and DMF/RTIL systems, probably due to the complicated interactions between the solvent and ionic liquid. Gel permeation chromatography traces of poly(methyl methacrylate) obtained by radiation polymerization in EtOH/RTIL and DMF/RTIL mixed solvent. Organic/RTIL (v/v): 1) 100:0; 2) 80:20; 3) 60:40; 4); 40:60; 5) 0:100. [source] | |||||||||||||