COPOLYMERIZATION OF STYRENE AND ALPHA-METHYLSTYRENE IN THE PRESENCE OF A CATALYTIC CHAIN TRANSFER AGENT

Copolymerizations of styrene (STY) and alpha-methylstyrene (AMS) have been performed at different monomer feed compositions and temperatures (40-70 degrees C) in the presence of the catalytic chain transfer age nt bis(boron difluorodimethylglyoximate)cobaltate(II) (COBF). The aver age chain transfer constant, [C-s], was found to increase approximatel y 3 orders of magnitude upon going from pure Sm to pure AMS. The addit ion of only 10% AMS increased the (Cs) by 1 order of magnitude. This b ehavior can be predicted from the relative fractions of growing radica l end groups, which results in the majority of polymer chains being fo rmed with an unsaturated AMS end group. No significant penultimate uni t effects in the chain transfer reaction were observed. The addition o f 10-20% AMS results in the majority of the growing radicals having AM S end groups, and hence AMS dominates the catalytic chain transfer rea ction. The [C-s] values continue to increase as the AMS content is inc reased beyond 20%; however, this can be mostly attributed to a decreas e in [k(p)] rather than an increase in [k(tr)]. The expected end group s in the homopolymerization of AMS in the presence of COBF were confir med by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS).