Radiation-Induced Polymerization of p-Halosubstituted Styrene

Abstract

The gamma-ray induced polymerization of p-chlorostyrene (Cl-St) and p-bromostyrene (Br-St), and the copolymerizations of these monomers with styrene (St) were studied in methylene chloride solution.
In the polymerization of Cl-St at 9°C, the kinetic order of the rate of polymerization (R_p) was 0.47 in reference to the dose rate. φ_γel (=φ_s/φ_m), which expresses the relative ratio of free radical production in the solvent and in the monomer, was determined as 5.4 from the effect of the monomer concentration on R_p. On the other hand, in the polymerization at -78°C, R_p was linearly proportional to the dose rate and the polymerization was strongly retarded by the addition of diethylamine (DEA).
In the copolymerization of Cl-St with St, the monomer reactivity ratios (MRR) at 9°C were almost same as those obtained by conventional radical initiators and MRR at -78°C coincided with those obtained by cationic catalysts. When copolymerized at -40°C, the intermediate values of MRR between those at 9°C and -78°C were obtained. MRR determined in the presences of DEA and DPPH were in good agreement with those at 9°C and -78°C without additives, respectively.
The similar results were also obtained in the polymerization of Br-St and the copolymerization of Br-St with St.
From these results, it was concluded that the polymerizations at 9°C and -78°C proceeded by radical and cationic mechanism, respectively, and the both mechanisms were simultaneouly operative at -40°C.