Cationic copolymerization of norbornadiene with styrene by AlEtCl2/tert-butyl chloride catalyst system, 1. Effect of norbornadiene/styrene feed ratio

The cationic copolymerization of norbornadiene (NBD) and styrene (St) was carried out with the AlEtCl2/tert-butyl chloride catalyst system in CH2Cl2 at −50°C, and the effect of NBD/St feed ratio on the solubility, the glass trtansition temperature (Tg) and the molecular weight of the copolymers was investigated. A soluble copolymer was prepared at 40 mol-% (or above) of St in the feed, although the NBD homopolymer comprised an insoluble fraction which might have been formed by a crosslinking reaction between the double bonds in the NBD units of the polymer. The copolymer has a statistically random sequence distribution of the two monomeric units not only in the polymer chain but also over the whole molecular weight range (from 103 to 106). The Tg of the amorphous copolymer is controlled by the NBD/St composition in the range from 100°C through 290°C. A soluble copolymer with highest Tg (ca. 170°C) could be prepared at a NBD/St feed ratio of 60/40 mol-%.