Synthesis and miscibility of comb poly[11-(4′-cyanophenyl-4"-phenoxy)undecyl acrylate]s prepared by ATRP

Comb poly[11-(4 ' -cyanophenyl-4 " -phenoxy)undecyl acrylate]s were synthesized by atom transfer radical polymerization (ATRP) of 11-[(4 ' -cyanophenyl-4 " -phenoxy)undecyl] acrylate from a multifunctional macroinitiator. The macroinitiator was prepared by first copolymerizing 2-[(2 ' -tetrahydropyranyl)oxy]ethyl acrylate (r(1) = 0.88) with 11-[(4 ' -cyanophenyl-4 " -phenoxy)undecyl] acrylate (r(2) = 1.11) under ATRP conditions, followed by hydrolysis of the randomly distributed tetrahydropyranyl groups and conversion of the resulting hydroxyethyl acrylate groups to 2-(2 ' -bromopropanoate)ethyl acrylate initiating sites. The comb polymers contained 45-128 repeat units according to GPC measurements relative to linear polystyrene or 52-237 repeat units according to GPC-RI-viscometry-right angle laser light scattering measurements. The biphasic regions of the smectic A to isotropic transition of the comb polymers with pdi = 1.27-1.87 are extremely narrow, with full widths at half of the maximum peak intensity (fwhm) = 2.38-8.28 degreesC, in contrast to that of the corresponding polymer prepared by conventional radical polymerization (fwhm = 17 degreesC). The breadth of the biphasic region of binary blends of the comb polymers with poly[11-(4 ' -cyanophenyl-4 " -phenoxy)undecyl acrylate]s of a variety of architectures (linear, three-arm star, comb) increases linearly with the difference in the end group (and therefore branching) density of the two components, regardless of the combination of molecular architectures.