Precision Polymerization and Polymers I. Synthesis and Conformation of Optically Active Poly(aromatic isocyanate)s.

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  • MAEDA Katsuhiro
    Department of Applied Chemistry, Graduate School of Engineering, Nagoya University
  • OKAMOTO Yoshio
    Department of Applied Chemistry, Graduate School of Engineering, Nagoya University

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Other Title
  • 精密重合・精密合成高分子Ｉ　　光学活性なポリ芳香族イソシアナートの合成と構造
  • コウガク カッセイ ナ ポリ ホウコウゾク イソシアナート ノ ゴウセイ ト

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Abstract

Achiral aromatic isocyanates were polymerized with various optically active anionic initiators in tetrahydrofuran (THF) at -98°C. Obtained polymers showed a much larger specific rotation than that expected from a chiral initiator residue introduced at the initial chain end (α-end). This result indicates that this optical activity is mainly due to a prevailing helical structure of a polymer caused by an optically active initiator residue attached to the α-end. Although it has been suggested that poly (aromatic isocyanate) s have a random coil conformation in solution, it became clear that the polymers can maintain a helical structure, even in solution, as well as poly (alkyl isocyanate) s can. In order to get information on the helical structure of poly (aromatic isocyanate) s, oligomers of aromatic isocyanates with a chiral residue at the α-end were synthesized and fractionated in terms of degree of polymerization using high-performance liquid chromatography (HPLC) or supercritical fluid chromatography (SFC) and their specific rotation was estimated. The chiroptical study of the obtained optically active oligomers indicated that in poly (aromatic isocyanate) s, helix reversals occur more often than in poly (alkyl isocyanate) s and the average persistence length of the helical structure of a polymer chain depends on the electric property of the substituent introduced on a phenyl group. Furthermore, optically active aromatic isocyanates were synthesized and polymerized with an achiral anionic initiator to obtain optically active polymers. The obtained polymers had a prevailing helical structure and showed the ability to discriminate enantiomers in CDCl3. This is the first example of chiral discrimination with polyisocyanate.

Journal

  • KOBUNSHI RONBUNSHU

    KOBUNSHI RONBUNSHU 54 (10), 608-620, 1997

    The Society of Polymer Science, Japan

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