SYNTHESIS AND SEGMENT CHARACTERIZATION OF POLYURETHANE STYRENE BLOCK COPOLYMERS PREPARED FROM POLYURETHANE MACROAZO INITIATORS

Aiming to obtain some detailed information for the radical block copolymerization initiated by macroazo initiators (MAI), azo-containing polyurethanes (PUMAI) were prepared by ternary polyaddition using an azobisalcohol, diol, and diisocyanate with easily characterizable chemical structures. The polyurethane segment was characterized after decomposition of azo groups in the PUMAI's. The PUMAI's initiated polymerization of styrene to give polyurethane-styrene block copolymers (PU-PS) as effectively as low molecular weight azo initiators. The PU-PS was purified by solvent extraction and the urethane bonds were decomposed to perform characterization of polystyrene segments with IR, H-1 NMR, and GPC. Film properties of the PU-PS's were also measured. The PU-PS's were found to have considerably high mono-dispersity with respect to both of the polymer segments. The PU-PS's were multi block copolymers composed of 3-5 units of PU/PS segments. Decomposition of the urethane bonds in PU-PS's will be used to produce terminally diol-containing telechelic polystyrene with high mono-dispersity. Adsorption chromatography will be useful for separation/purification of the block copolymers.