Preparation of α-, ω-End-Functionalized Poly(n-hexyl isocyanate) Heterotelechelics

Abstract

α- and ω-End-functionalized heterotelechelic poly(n-hexyl isocyanate) (PHIC) has been prepared by living coordination polymerization of HIC using benzyloxydichloro(cyclopentadienyl)titanium(IV) (BzCpTiCl2) (1) or 2-methacryloyloxyethoxydichloro(cyclopentadienyl)titanium(IV) (HEMACpTiCl2) (2) as an initiator, followed by heterogeneous termination with carboxylic anhydrides in the presence of a Lewis acid. The use of acetic (AAn), methacrylic (MAAn), butyric, n-hexanoic, and maleic anhydrides as a terminator, and trialkyl aluminum compounds, including trimethyl, triethyl, and triisobutyl, and boron trifluoride-diethyl etherate (BF3OEt2) as a Lewis acid were examined in the termination reaction. The effect of experimental conditions in the termination reaction on the yield of recovered polymer and ω-end-functionality have been examined and optimized. Using BF3OEt2 as a Lewis acid and AAn or MAAn as a terminator, several α- and ω-PHIC heterotelechelics having α-benzyloxy-ω-acetyl (Bz-HIC-n-Ac, where n is the degree of polymerization of HIC), α-benzyloxy-ω-methacryloyl (Bz-HIC-n-MA), and α-2-methacryloyloxyethoxy-ω-acetyl (MA-HIC-n-Ac) groups could be successfully prepared with quantitative recovery (>98%) and functionality (∼100%). The thermal stability of the end-functionalized heterotelechelic PHICs in benzene were found to be remarkably enhanced, when compared to that of the corresponding ω-hydrogen-terminated compound (Bz-HIC-n-H).