Kinetics and mechanism of cationic epoxide copolymerization

The kinetics and mechanism of copolymerization of epoxyalkanes [epoxypropane ( 2a ), 1‐chloro‐2,3‐epoxypropane ( 2b ), and 2,3‐epoxy‐1‐propyl nitrate ( 2c ) (glycide nitrate)] with tetrahydrofurane by BF 3 were investigated. Kinetic and molecular weight regularities were established and copolymerization constants were determined. The formation of cyclic tetramers of the epoxyalkanes was found to be a characteristic feature of homo‐ and copolymerization. Reactions yielding double bonds at the end and hydroxylic groups and such hindering chain growth were investigated. From a large class of phenomena the hypothesis was derived that the growing polymer chain represents a “cyclic” zwitterion and the active center is an ion pair. A number of facts in favour of the carbonium nature of the polymerization centers was established.