Synthesis of Novel Multifunctional Polyisobutylenes at Chain End(s) and Their Application to AnB Asymmetric Star and AnBAn Pompom Polymers by Combination of Living Cationic and Anionic Polymerizations

Abstract

The synthesis of an array of ω- or α,ω-multifunctional polyisobutylenes (PIBs) with 2, 4, and 8 benzyl bromide moieties has been demonstrated by an iterative divergent methodology using ω- or α,ω-functional PIBs with allyl halide moiety (moieties) as starting materials. The multifunctional PIBs were successfully applied for the synthesis of A2B, A4B, and A8B asymmetric star polymers as well as A2BA2, A4BA4, and A8BA8 pompom polymers where A and B were poly(methyl methacrylate) (PMMA) and PIB segments, respectively. The synthetic method involved the coupling reaction of living PMMA with multifunctional PIBs in tetrahydrofuran at −40 °C. The coupling efficiencies were virtually quantitative in all cases. The well-defined structures of the resulting branched polymers were confirmed by size exclusion chromatography−right angle laser light scattering and 1H NMR analyses. The microphase-separated morphologies of all AnBAn type pompom polymers were supported by differential scanning calorimetry. The stress−strain plots of solution-cast films of AnBAn type pompom polymers showed good elastomeric properties (279−444% elongations at break and 12.6−20.7 MPa tensile strengths).