Carboxy-terminated homo- and copolymers of styrene using dicarboxylic acid-functional azo initiator and 2,2,6,6-tetramethyl-1-piperidyloxyl (TEMPO)

Carboxy-terminated polystyrene, poly(styrene-co-acrylonitrile), and polystyrene-block-poly(styrene-co-acrylonitrile) with ratios of weight- to number-average molar masses M?_w/M?_n below 1.3 were synthesized via a controlled radical polymerization mechanism. The polymerizations were initiated with 4,4′-azobis(4-cyanopentane-carboxylic acid) and 2,2,6,6-tetramethyl-1-piperidyloxyl radical and conducted in bulk at elevated temperatures. The polymerization was monitored by nuclear magnetic resonance, size-exclusion chromatography, end-group titration and differential scanning calorimetry.