In the bulk copolymerization of 1-chloro-1,3-butadiene (CB) and styrene (St) at 70°C, the copolymerization rate, monomer reactivity ratio (MRR), and elementary reactions governing the molecular weight of the copolymer were studied. The rate of St polymerization decreased drastically by the addition of a small amount of CB, suggesting a predominant cross-over termination, (kt12). MRRs found: rCB=1.680 and rSt=0.274, hence Q=1.80 and e=0.081 for CB. The molecular weight of copolymer and its polydispersity decreased with an increase in CB concentration, which is interpreted by a large kt12 value. When the CB concentration becomes large, termination between CB polymer radicals may also become important.

The copolymer of 1-chloro-1,3-butadiene (CB) and styrene (St) was synthesized and its composition and distribution in poly(CB-co-St) were investigated by thin-layer chromatography (TLC). The concentration gradient development method of a tetrahydrofuran–cyclohexane mixture was useful for separating the copolymer into its components. Resolution by molecular weight was not significant under the present conditions. The experimental results on the compositional distribution of poly(CB-co-St)s obtained at high conversion were in close agreement with the values calculated from the monomer reactivity ratios and conversion. Also, the composition of the copolymers having a CB content too small for ordinary elemental analysis to be applicable could be assayed by TLC. The observed CB content was below 1 mol%, and agreed well with that calculated.