| 초록 |
Cationic ring-opening copolymerization of tetrahydrofuran (THF) and ethylene oxide (EO) leaded to hydroxyl-terminated polyether, and it was carried out by use BF3O(C2H5)2 as catalyst in the presence of 1,4-butanediol as initiator. Various concentration ratios of [catalyst]/[1,4-butanediol], [monomer]/[1,4-butanediol] affected molecular weight and yield, and feed ratio of EO/THF determinated the mole precent of EO and THF units in copolymer. In this system, molecular weight of poly(EO-co-THF) was merely dependant on the ratio of [monomer]/[butanediol], but not on catalyst. It showed that this cationic copolymerization follow activated monomer mechanism (AMM), which overwhelmingly took more weight than activated chain end (ACE) mechanism that held great inclination to side reaction (i. e. oligomeric cyclic ether), and well-fined linear products are obtained. It followed from kinetic considerations, that in order to achieve the high contribution of AMM, the reaction should be carried out at low instantaneous monomer concentration, and this was accomplished by droplet addition of monomer mixture. |
