The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Andrew K. Whittaker - One of the best experts on this subject based on the ideXlab platform.
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A study of the radiation degradation of styrene/alkane and α-methylstyrene/alkane copolymers
Polymer International, 2003Co-Authors: Francisco Cardona, David J. Hill, Peter J. Pomery, Andrew K. WhittakerAbstract:The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and Alpha-Methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross-section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using C-13 NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in Alpha-Methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in Alpha-Methylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.
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A study of the radiation degradation of styrene/alkane and α-methylstyrene/alkane copolymers
Polymer International, 2003Co-Authors: Francisco Cardona, David J. Hill, Peter J. Pomery, Andrew K. WhittakerAbstract:The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and Alpha-Methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross-section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using C-13 NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in Alpha-Methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in Alpha-Methylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.
Richard G. Jones - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and characterization of poly(methylphenylsilylene)– poly(methyl methacrylate) block copolymers
Polymer International, 1998Co-Authors: Laurence Lutsen, Richard G. JonesAbstract:Block copolymers of poly(methylphenylsilylene) and poly(methyl methacrylate) have been synthesized by condensation of alpha,omega-dichloropoly(methylphenylsilylene) with poly(methyl methacrylate)-lithium. The alpha,omega-dichloropoly(methylphenylsilylene) was synthesized by the Wurtz-type reductive coupling of dichloromethylphenylsilane using sodium in boiling toluene and poly(methyl methacrylate)-lithium was prepared by anionic polymerization of methyl methacrylate in tetrahydrofuran initiated by Alpha-Methylstyrene-lithium/LiCl. The structures of the block copolymers have been confirmed using size exclusion chromatography and NMR spectroscopy. (C) 1998 SCI.
Francisco Cardona - One of the best experts on this subject based on the ideXlab platform.
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A study of the radiation degradation of styrene/alkane and α-methylstyrene/alkane copolymers
Polymer International, 2003Co-Authors: Francisco Cardona, David J. Hill, Peter J. Pomery, Andrew K. WhittakerAbstract:The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and Alpha-Methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross-section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using C-13 NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in Alpha-Methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in Alpha-Methylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.
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A study of the radiation degradation of styrene/alkane and α-methylstyrene/alkane copolymers
Polymer International, 2003Co-Authors: Francisco Cardona, David J. Hill, Peter J. Pomery, Andrew K. WhittakerAbstract:The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and Alpha-Methylstyrene/alkane copolymers have been studied. The primary radical species formed on radiolysis of the copolymers at 77 K, and identified by ESR spectroscopy, are the same as those formed during radiolysis of the homopolymers. The yields of radicals for the copolymer are as predicted assuming that the cross-section is proportional to the electron density of each component; however, there is some evidence of radical migration to aromatic groups at 77 K. Changes in molecular structure on irradiation were detected by using C-13 NMR spectroscopy. Evidence of the consumption of terminal double bonds, and chain scission in Alpha-Methylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in Alpha-Methylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.
Rudolf Faust - One of the best experts on this subject based on the ideXlab platform.
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Polyisobutylene-Based Thermoplastic Elastomers. 3. Synthesis, Characterization, and Properties of Poly(.alpha.-methylstyrene-b-isobutylene-b-.alpha.-methylstyrene) Triblock Copolymers
Macromolecules, 1995Co-Authors: Rudolf FaustAbstract:The first efficient synthesis of poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) (PαMeSt-PIB-PαMeSt) triblock copolymer thermoplastic elastomers (TPEs) has been accomplished by living cationic polymerization using sequential monomer additions. Living PIB was prepared by the 5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene (tBuDicumcl)/TiclJHex :Mecl 60 :40 v :v/-80°C polymerization system. The living ends were capped by 1,1-diphenylethylene (DPE). TiCl 4 was replaced by SnBr 4 , followed by the addition of αMeSt. Triblock copolymers with close to theoretical molecular weights and narrow molecular weight distributions (M w /M n ∼1.1) were obtained. Homopolymer and diblock contamination have been found to be negligible. The thermal stability of the triblock copolymer was characterized by thermogravimetric analysis. Microphase separation was evidenced by the two glass transitions (at -65 and +180°C) observed by differential scanning calorimetry and in dynamic mechanical analysis. Triblock morphology was examined by transmission electron microscopy. Compression-molded samples with 16-45 wt % PαMeSt exhibited 12-24.5 MPa tensile strength, apparently directly related to the PαMeSt content and independent of the PIB molecular weight.
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Living Carbocationic Sequential Block Copolymerization of Isobutylene with .alpha.-Methylstyrene
Macromolecules, 1995Co-Authors: Rudolf FaustAbstract:The polymerization of α-methylstyrene (αMeSt) was investigated using the 2-chloro-2,4,4-trimethylpentane (TMPClTiCl 4 /methyl chloride :hexane (40 :60, v :v)/-80 °C system as a model to determine the efficiency of crossover from living polyisobutylene (PIB) to αMeSt. Low initiator efficiencies and broad molecular weight distributions were obtained. Living polymerization of αMeSt was achieved by first converting TMPCl to the corresponding diphenylalkylcarbenium ion by capping with 1,1-diphenylethylene (DPE), followed by the addition of titanium(IV) alkoxide to decrease the Lewis acidity. The initiator efficiencies, however, were lower than 100%. Living polymerization with ∼100% initiator efficiency was achieved by SnBr 4 as coinitiator. First, TMPCl is transformed to the corresponding diphenylalkylcarbenium ion by capping with 1,1-diphenylethylene. Subsequently, titanium(IV) isopropoxide is introduced to deactivate TiCl 4 , followed by the addition SnBr 4 and αMeSt. The success of the method was demonstrated by the synthesis of PIB-poly(α-methylstyrene) diblock copolymers without homopolymer contaminants.
Laurence Lutsen - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and characterization of poly(methylphenylsilylene)– poly(methyl methacrylate) block copolymers
Polymer International, 1998Co-Authors: Laurence Lutsen, Richard G. JonesAbstract:Block copolymers of poly(methylphenylsilylene) and poly(methyl methacrylate) have been synthesized by condensation of alpha,omega-dichloropoly(methylphenylsilylene) with poly(methyl methacrylate)-lithium. The alpha,omega-dichloropoly(methylphenylsilylene) was synthesized by the Wurtz-type reductive coupling of dichloromethylphenylsilane using sodium in boiling toluene and poly(methyl methacrylate)-lithium was prepared by anionic polymerization of methyl methacrylate in tetrahydrofuran initiated by Alpha-Methylstyrene-lithium/LiCl. The structures of the block copolymers have been confirmed using size exclusion chromatography and NMR spectroscopy. (C) 1998 SCI.
