Synthesis and characterization of graft copolymers based on poly(p-phenylene terephthalamide) backbone and well-defined polystyrene side chains

A novel dualfunctional monomer, 2-(2',2',6',6'-tetramethyl-piperidinyl-1'-oxy)methylbenzene-1,4-dioyl chloride hydrochloride, with two acid chloride groups for step-growth polymerization and a nitroxide group for the mediation of living radical polymerization was synthesized. It was first copolymerized with terephthaloyl chloride and p-phenylenediamine at a feed molar ratio of 1:3:4 in N-methyl-2-pyrrolidone containing 10 wt% calcium chloride at -10A degrees C to yield a poly(p-phenylene terephthalamide) based macroinitiator, which initiated radical polymerization of styrene at 125A degrees C to obtain a series of poly(p-phenylene terephthalamide)-g-polystyrenes. A combinatory analysis of proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elementary analysis, thermogravimetry and gel permeation chromatography indicated that the macroinitiator induced the radical polymerization of styrene to proceed in a well-controlled way. The molecular weight of side-chains increased with an increase of monomer conversion, and the molecular weight distribution index remained lower than 1.5. The graft copolymers showed a remarkably improved solubility in N-methyl-2-pyrrolidone and much depressed crystallinity in bulk.