Complex Macromolecular Architectures Based on <i>n</i>-Hexyl Isocyanate and ϵ-Caprolactone Using Titanium-Mediated Coordination Polymerization

Abstract

Well-defined diblock copolymers {PS-b-P(ϵ-CL)} and triblock terpolymers {PS-b-PI-b-P(ϵ-CL), PI-b-PS-b-P(ϵ-CL)} of polystyrene, PS, poly(ϵ-caprolactone), P(ϵ-CL), and polyisoprene, PI, were synthesized using CpTiCl2(OP) (P = PS, PS-b-PI, or PI-b-PS) as macroinitiator. Graft copolymers having polybutadiene, PBd, backbone and poly(n-hexyl isocyanate), PHIC, or P(ϵ-CL) branches {PBd-g-PHIC and PBd-g-P(ϵ-CL)} as well as block−graft terpolymers {PS-b-(PI-g-PHIC), PS-b-[PI-g-P(ϵ-CL)]} were also synthesized by performing hydroboration/oxidation reactions on the polydiene backbone and by transforming the introduced hydroxyl groups to initiation sites by reaction with CpTiCl3. Finally, PS(PHIC)2 and PS[P(ϵ-CL)]2 3-miktoarm star copolymers were synthesized using a heterofunctional initiator bearing one initiation site for atom transfer radical polymerization and two for titanium-mediated coordination polymerization. All intermediates and final products were characterized by size exclusion chromatography, equipped with refractive index and light scattering detectors, membrane osmometry, and 1H NMR spectroscopy.