Preparation and characterization of graft copolymers of methyl methacrylate and poly(n-hexyl isocyanate) macromonomers

Living poly(n-hexyl isocyanate) (PHIC) was deactivated with methacryloyl chloride to produce methacryl-terminated poly(n-hexyl isocyanate) (PHIC-MA) rodlike macromonomers. Radical copolymerization of methyl methacrylate (MMA) with PHIC-MA was performed using 2,2′-azobis(isobutyronitrile) as an initiator in benzene at 60 °C to prepare poly(methyl methacrylate)-graft-poly(n-hexyl isocyanate) (PMMA-graft-PHIC) graft copolymers. The monomer reactivity ratios of MMA (M₁) and PHIC-MA (M₂) were evaluated as r₁=11.5 and r₂=∼0, exhibiting remarkably lower reactivity of PHIC-MA macromonomer than that of common macromonomers. The resultant graft copolymers were characterized using gel permeation chromatography equipped with low-angle laser light-scattering to determine the molecular weights, and equipped with a refractive index detector and an ultraviolet light detector to estimate a PHIC weight fraction of PMMA-graft-PHIC at the ith elution volume of the GPC chromatogram. There are 2-3 PHIC grafts per PMMA molecule, and the PHIC rodlike chains might be difficult to introduce into the PMMA main chains having higher molecular weights. A specific dimension of PMMA-graft-PHIC in solution was discussed in detail.