Cationic polymerization of cyclopentadiene with SnCl4: Control of molecular weight and narrow molecular weight distribution

Precise control of molecular weights and their distributions (MWD) in catio nic polymerization of cyclopentadiene (CPD) has been achieved with a three- component initiating system: the HCl adduct of CPD or a vinyl ether(initiat or), SnCL4 (Lemis acid catalyst), and n-Bu4NCl (additive), in dichlorometha ne at -78 degreesC. The number-average molecular weights of the polymers in creased in direct proportion to monomer conversion as well as to the monome r-to-initiator mole ratio (up to 200), and the MWDs were narrow throughout the reactions (M-w/M-n = 1.2-1.3); those in the additive-free systems were dearly broader (M-w/M-n > 21. Weak bases such as diethyl ether and ethyl ac etate were also effective additives, whereas THF inhibited the polymerizati on. The poly(CPD) was completely soluble in organic solvents, carried the i nitiator fragment at the a-end (nearly one per chain!, and consisted of nea rly equal amounts of 1,2-and 1.4-repeat units, free from other enchainments .