Polymerization of n-hexyl isocyanate with CpTiCl₂(OR) (R = functional group or macromolecular chain): A route to ω-functionalized and block copolymers and terpolymers of n-hexyl isocyanate

Well-defined ω-cholesteryl poly(n-hexyl isocyanate) (PHIC-Chol), as well as diblock copolymers of n-hexyl isocyanate (HIC) with styrene, PS-b-PHIC [PS = polystyrene; PHIC = poly(n-hexyl isocyanate)], and triblock terpolymers with styrene and isoprene, PS-b-PI-b-PHIC and PI-b-PS-b-PHIC (PI = polyisoprene), were synthesized with CpTiCl₂(OR) (R = cholesteryl group, PS, or PS-b-PI) complexes. The synthetic strategy involved the reaction of the precursor complex CpTiCl₃ with cholesterol or the suitable ω-hydroxy homopolymer or block copolymer, followed by the polymerization of HIC. The ω-hydroxy polymers were prepared by the anionic polymerization of the corresponding monomers and the reaction of the living chains with ethylene oxide. The reaction sequence was monitored by size exclusion chromatography, and the final products were characterized by size exclusion chromatography (light scattering and refractive-index detectors), nuclear magnetic resonance spectroscopy, and, in the case of PHIC-Chol, differential scanning calorimetry.