SYNTHESIS AND CHARACTERIZATION OF POLY[1,4-ISOPRENE-B-(ETHYLENE OXIDE)] AND POLY[ETHYLENE-CO-PROPYLENE-B-(ETHYLENE OXIDE)] BLOCK-COPOLYMERS

The synthesis of amphiphilic AB block copolymers, having 1,4-polydiene or corresponding hydrogenated aliphatic polyolefin blocks and poly(et hylene oxide) (PEO) blocks, is described. The materials are obtained i n a two-step process. In the first step isoprene is polymerized anioni cally in a hydrocarbon solvent with sec-butyllithium or tert-butyllith ium as initiator. The end-capping of the living polymer with ethylene oxide (EO) yields polyisoprene, which is functionalized with a hydroxy l end group (PI-OH). This product can be hydrogenated to the aliphatic polyolefin poly(ethylene-co-propylene) (PEP-OH). In the second step c umylpotassium is used to deprotonate the OH groups, leading to the mac roinitiators PI-OK and PEP-OK. PI-PEG and PEP-PEO block copolymers are obtained by initiating the polymerization of EO with the macroinitiat ors in TKF. The characterization reveals narrow molecular weight distr ibutions, absence of homopolymer in the block copolymers, and complete conversion of monomers in both polymerization steps. The materials fo rm water soluble aggregates even at a PEO content of 41% and a total m olecular weight of M(n) = 35400. In n-decane all block copolymers synt hesized were soluble, the one with the smallest hydrophobic part havin g a PI content of 24% and a total molecular weight of M(n) = 17700.