Preparations of Triphenylmethyl Salts and Their Use in the Cationic Polymerization of α-Methylstyrene. Counteranion and Polymer Structure

Kunitake, Toyoki; Tsugawa, S.

doi:10.1021/ma60048a007

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1981

2016

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The counterion effect on the steric course of the cationic polymerization of tert‐butyl vinyl ether

Kunitake

Takarabe

1981

Makromol. Chem.

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The cationic polymerization of tert-butyl vinyl ether was carried out at -76 "C with a variety of triphenylmethyl salts as initiator. The microtacticity of the polymer was determined by 'H NMR spectroscopy after conversion to poly(viny1 alcohol). The fraction of isotactic units, P,,,, increased with decreasing polarity of the polymerization medium, i n consistence with the published data for metal halide initiators. The P,,, value decreased gradually from 0,85 tp 0,72 -0,75 in 7 : 3 (v/v) CH,Cl,-toluene by increasing the counteranion radius from 2,4 A (BF;) to ca. 4 A (AlClh). A further increase in the counteranion size, however, did not notably influence the steric structure of the polymer. These structure variations are discussed in terms of the steric course of cationic propagation. In the case of pentacoordinate counteranions (SnCI; and ZrC1; ), the steric structure depended also on the counteranion concentration, as already reported for other monomers. a) Contribution No. 553 from this department.

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