Novel star-block polymers: Three polyisobutylene-b-poly(methyl methacrylate) arms radiating from an aromatic core

A series of novel three-arm star blocks consisting of three polyisobutylene -b-poly(methyl methacrylate) (PIB-b-PMMA) diblocks radiating from a tricumy l core were synthesized, characterized, and tested. The synthetic strategy involved three steps: the synthesis of Cl-t-tritelechelic PIE by living cat ionic isobutylene (IB) polymerization, the conversion of the Cl-t termini t o isobutyryl bromide groups, and the initiation of Living radical methyl me thacrylate (MMA) polymerization by the latter groups. The PIE and PMMA segm ent lengths (M-n's) could be controlled by controlling the conditions of th e living cationic and radical polymerizations of IB and MMA, respectively. Core destruction analysis directly proved the postulated three-arm microarc hitecture. The structures of the products were analyzed by H-1 NMR and Four ier transform infrared spectroscopies, and their thermal properties were an alyzed by differential scanning calorimetry and thermogravimetric analysis. The presence of a low- and a high-temperature glass transition (T-g,T-PIB similar to -63 degrees C, T-g,T-PMMA similar to 120 degrees C) indicated a phase-separated micromorphology. Stress/strain analysis showed a tensile st rength of up to similar to 22.9 MPa and an elongation of similar to 200%. ( C) 2000 John Wiley & Sons, Inc.