Synthesis of Methacrylate-Ended Poly(n-hexyl isocyanate) Rodlike Macromonomers and Their Radical Copolymerization Behavior

Methacrylate-ended rodlike macromonomers consisting of poly( n -hexyl isocyanate) (MA-HIC- n ( 2 ), where n is a degree of polymerization of n -hexyl isocyanate (HIC)) with narrow molecular weight distribution have successfully been synthesized in CH 2 Cl 2 at room temperature by living coordination polymerization of HIC using 2-methacrylate ethyloxydichloro(cyclopentadienyl)titanium (IV) ( 1 ) as an initiator. The rodlike macromonomers prepared have carefully been characterized by size exclusion chromatography fitted with a multiangle laser light scattering (SEC−MALS) and 1 H NMR spectroscopy. The radical copolymerization behavior of the rodlike macromonomers (M 2 ) with methyl methacrylate (MMA) (M 1 ) or styrene (ST) (M 1 ) in benzene at 60 °C has thoroughly been studied and rationalized with a function of degree of polymerization of HIC. In region of degree of polymerization ( n ) higher than 26, the macromonomer's apparent reactivity (1/ r 1 ) relative to MMA was found to be almost independent of n and macromonomer concentration but lower than MMA (1/ r 1 is ca. 0.6). On the other hand, in the macromonomers with n less than 26, the reactivity appeared to steeply increase with decreasing n, because of weak aggregation due to hydrogen bond formation between terminal amide groups in benzene. In the copolymerization with ST (M 1 ), the apparent reactivities (1/ r 1 ) were also lower the reference value reported in the copolymerization of MMA with ST. The copolymerization behavior of MA-HIC- n macromonomers was compared with that of styryl-ended (VB-HIC- n, 1/ r 1 ≈ 1.0) and methacryloyl-ended (Bz-HIC- n -MA, 1/ r 1 ≈ 0.1) macromonomers and discussed from the structural point of views. The methacrylate functional group was thought to be much more subject to steric hindrance effects than the styrenic group.