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 tricumyl core were synthesized, characterized, and tested. The synthetic strategy involved three steps: the synthesis of Clt -tritelechelic PIB by living cationic isobutylene (IB) polymerization, the conversion of the Clt termini to isobutyryl bromide groups, and the initiation of living radical methyl methacrylate (MMA) polymerization by the latter groups. The PIB and PMMA segment lengths (Mn 's) could be controlled by controlling the conditions of the living cationic and radical polymerizations of IB and MMA, respectively. Core destruction analysis directly proved the postulated three-arm microarchitecture. The structures of the products were analyzed by 1H NMR and Fourier transform infrared spectroscopies, and their thermal properties were analyzed by differential scanning calorimetry and thermogravimetric analysis. The presence of a low- and a high-temperature glass transition (Tg,PIB ∼ −63°C, Tg,PMMA ∼ 120°C) indicated a phase-separated micromorphology. Stress/strain analysis showed a tensile strength of up to ∼ 22.9 MPa and an elongation of ∼ 200%.