Photo-Probe Study of Siloxane Polymers(2)Local Structure and Dynamics of MQ-Type Silicone Resin Probed by Fluorescence Depolarization of Perylene

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  • YOSHII Kimihiko
    Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
  • MACHIDA Shinjiro
    Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
  • HORIE Kazuyuki
    Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
  • ITOH Maki
    Dow Corning Asia Ltd., Research Center, 603 Kishi, Yamakita, Kanagawa 258-0112, Japan

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  • Photo-Probe Study of Siloxane Polymers. II. Local Structure and Dynamics of MQ-Type Silicone Resin Probed by Fluorescence Depolarization of Perylene.

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説明

We investigated the local structure and dynamics of three-dimensionally crosslinked polysiloxane, an MQ-type silicone resin, using fluorescence depolarization of perylene molecularly dispersed in the resin. Rotational diffusion coefficient, Dr, of perylene was determined in uncured and cured MQ resins and in PMMA over a temperature range of 90-300K. Dr in the uncured MQ resin (a mixture of prepolymers), i.e., an assembly of crosslinked nanometer-scale particles, is 5-10×108S-1 at room temperature and shows continuous drastic decrease with decreasing temperature to 106S-1 at 90K. Dr in the cured MQ resins is 107S-1 and almost independent of temperature. Dr in the cured MQ resins is thus larger than that in the uncured prepolymer at 90K. A possible explanation is as follows. The thermal fluctuation of nanoparticles caused by the Si-O-Si chain flexibility becomes weak with decreasing temperature in the uncured prepolymer, and change in packing and dense aggregation of the nanoparticles around perylene molecules cause the gradual increase in restriction against rotation of perylene from room temperature to 90K. In the cured MQ resins, hydrosilylation curing reaction would fix the spatial position of the nanoparticles and retain the local space around perylene even at low temperatures. The results of fluorescence depolarization are compared with those of photoisomerization of azobenzene in the MQ resin in our previous study.

収録刊行物

  • Polymer Journal

    Polymer Journal 32 (1), 37-42, 2000

    The Society of Polymer Science, Japan

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