Controlled Cationic Polymerization of 1‐Methoxy‐1,3‐Butadiene: Long‐Lived Species‐Mediated Reaction and Control over Microstructure with Weak Lewis Bases

Abstract

Controlled cationic polymerization of trans-1methoxy-1,3-butadiene was achieved through the design of appropriate initiating systems, yielding soluble polymers with controllable molecular weights. The combined use of SnCl 4 or GaCl 3 as a Lewis acid catalyst and a weak Lewis base in conjunction with HCl as a protonogen resulted in efficient and controlled polymerization. The M n values of the product polymers increased linearly along the theoretical line, which indicates that intermolecular crosslinking reactions negligibly occurred. In addition, the polymer microstructure was critically dependent on the weak Lewis base employed. In particular, the use of tetrahydrofuran as an additive resulted in the highest 4,1/4,3-structure ratio (96/4). Weak Lewis bases also affected the polymerization rates but exhibited unique trends that differed from their effects on the cationic polymerization of alkyl vinyl ethers.