Stereospecific Polymerization of Acrylonitrile Using Acrylonitrile–Urea Canal Complex Initiated by γ-Ray Irradiation: Roles of Radical Chain Transfer Reagents

Abstract

An attempt was made to clarify the effect of polymerization conditions (e.g., the content of chain transfer reagent, irradiation dose, acrylonitrile (AN)–urea ratio, aging time) on the stereoregularity, the viscosity-average molecular weight Mv, and the conversion in the radiation-induced polymerization of AN–urea canal complex in the presence of radical chain transfer reagent including alkyl mercaptans, alkylamines, alkyl alcohols and chloroform. The addition of n-butyl mercaptan (n-BM) to AN–urea system slowed down the rate of the canal complex formation and decreased the amount of the canal complexes formed. The role of n-BM on the formation of AN–urea canal complex was also examined by DSC. The enthalpy of fusion (ΔH) of AN solid in AN–n-BM–urea system decreased with elapse of aging time, although ΔH of n-BM was almost constant in the whole range of aging time. From these findings, it was concluded that n-BM is not included in the AN–urea canal complex. The conversion decreased remarkably with an increase in n-BM content. When 2 mol%/AN of n-BM was added to AN, Mv was almost constant (ca. Mv=2.0×105), irrespective of the amount of n-BM added. Addition of n-BM to AN–urea system brings about a small, but significant increase in the content of isotactic triad (mm) by 5 to 14%.