GRAFTING ON POLYBUTADIENE WITH MACRO OR MACROMONOMER INITIATORS CONTAINING POLY(ETHYLENE GLYCOL) UNITS

Crosslinked poly(ethylene glycol)-block-polybutadiene block copolymers were obtained by coupling reaction of polybutadiene (PBd) with macromonomer azo initiators (macroinimers) or polyazoesters (PAE) in moderate yield (22-75%). NMR and FT-IR spectroscopy measurements were used to characterize and determine the poly(ethylene glycol) (PEG) contents (20-66%). The latter depends on the initial concentration of the azo compounds. Broad melting peaks appear in the DSC curves in a temperature range from about 65-130 degrees C. The crosslinked polymers containing PEG-1500 units showed sharp melting transitions and the second heating cycle showed that recrystallization rates are very high. Swelling ratios of the polymer networks were determined in water (1,22-2,96) and in CHCl3 (7,81 -20,84). The morphology of the cold fractured area of the crosslinked polymers was analyzed by scanning electron microscopy (SEM).