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Alpha Methylstyrene

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Rudolf Faust – One of the best experts on this subject based on the ideXlab platform.

  • Polyisobutylene-Based Thermoplastic Elastomers. 3. Synthesis, Characterization, and Properties of Poly(.Alpha.-Methylstyrene-b-isobutylene-b-.Alpha.-Methylstyrene) Triblock Copolymers
    Macromolecules, 1995
    Co-Authors: Rudolf Faust

    Abstract:

    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.

  • Living Carbocationic Sequential Block Copolymerization of Isobutylene with .Alpha.-Methylstyrene
    Macromolecules, 1995
    Co-Authors: Rudolf Faust

    Abstract:

    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.

Andrew K. Whittaker – One of the best experts on this subject based on the ideXlab platform.

  • A study of the radiation degradation of styrene/alkane and α-Methylstyrene/alkane copolymers
    Polymer International, 2003
    Co-Authors: Francisco Cardona, David J. Hill, Peter J. Pomery, Andrew K. Whittaker

    Abstract:

    The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and AlphaMethylstyrene/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 AlphaMethylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in AlphaMethylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.

  • A study of the radiation degradation of styrene/alkane and α-Methylstyrene/alkane copolymers
    Polymer International, 2003
    Co-Authors: Francisco Cardona, David J. Hill, Peter J. Pomery, Andrew K. Whittaker

    Abstract:

    The effects of copolymer composition and microstructure on the radiation chemistry of styrene/alkane and AlphaMethylstyrene/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 AlphaMethylstyrene/alkane copolymers was found. Measurements of viscosity supported the mechanism of cross-linking predominating in styrene/alkane copolymers, while in AlphaMethylstyrene/alkane copolymers chain scission was the major result of irradiation. (C) 2003 Society of Chemical Industry.

Maria Inês Bruno Tavares – One of the best experts on this subject based on the ideXlab platform.

  • Carbon-13 solution and solid-state NMR investigation of AlphaMethylstyrene-co-acrylonitrile
    Journal of Applied Polymer Science, 2002
    Co-Authors: Regina F. Nogueira, Maria Inês Bruno Tavares

    Abstract:

    Nuclear magnetic resonance spectroscopy (NMR) gave information on the behavior of AlphaMethylstyrene-co-acrylonitrile. The comonomer sequence distribution in the copolymer and the depolymerization process were detected by solution analysis. The solid-state NMR investigation showed that 13C routine spectra such as MAS and CPMAS allowed one to obtain information on the molecular domains of chains and also permitted evaluation of the domains’ mobility. In this case, the mobile domain was formed by AlphaMethylstyrene (AMS). The variable contact time and the proton spin-lattice relaxation time in the rotating-frame parameter were determinant factors to evaluate the dynamic molecular behavior and the homogeneity of the comonomer distribution along the copolymer chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 138–143, 2002; DOI 10.1002/app.10275

  • Carbon-13 NMR study of poly(AlphaMethylstyrene)
    Polymer Testing, 2001
    Co-Authors: Regina F. Nogueira, Maria Inês Bruno Tavares

    Abstract:

    Abstract Nuclear magnetic resonance spectroscopy (NMR) in solution and solid state was applied to obtain response of the chemical behaviour of commercial poly(AlphaMethylstyrene) (PAMS). From solution measurements it was possible to determine the microstructure of this amorphous homopolymer. The solid state NMR investigation showed that the CPMAS 13 C routine spectrum allowed us to obtain information on the polymer microstructure and also evaluate the domain mobilities. The variation contact time and the proton spin-lattice relaxation time were determinant factors to evaluate the dynamic molecular motion.

  • carbon 13 nmr study of poly Alpha Methylstyrene
    Polymer Testing, 2001
    Co-Authors: Regina F. Nogueira, Maria Inês Bruno Tavares

    Abstract:

    Abstract Nuclear magnetic resonance spectroscopy (NMR) in solution and solid state was applied to obtain response of the chemical behaviour of commercial poly(AlphaMethylstyrene) (PAMS). From solution measurements it was possible to determine the microstructure of this amorphous homopolymer. The solid state NMR investigation showed that the CPMAS 13 C routine spectrum allowed us to obtain information on the polymer microstructure and also evaluate the domain mobilities. The variation contact time and the proton spin-lattice relaxation time were determinant factors to evaluate the dynamic molecular motion.