Complex macromolecular architectures based on n-hexyl isocyanate and ε-caprolactone using titanium-mediated coordination polymerization

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.