NOVEL PALYISOBUTYLENE POLY(DIMETHYLSILOXANE) BICOMPONENT NETWORKS - II - NETWORK STRUCTURE AND PROPERTY CHARACTERIZATION/

The first part of this series concerned the synthesis of novel polyiso butylene (PIB)/poly(dimethylsiloxane)( PDMS) bicomponent networks; the present paper concerns the structure and property characterization of a series of bicomponent networks of varying compositions (PIB wt %/PD MS wt % = 92/8, 70/30, 50/50, 35/65) having average molecular weights between crosslinks ((M) over bar(c)) of similar to 20,000 g/mol. Accor ding to network structure analysis by uniaxial equilibrium stress-stra in measurements, the experimental (M) over bar(c)'s are in excellent a greement with theoretical values. Hydrosilation end-linking efficiency was quantitated by the amount of sol and functional group analysis by H-1-NMR spectroscopy. NMR evidence indicates double-bond isomerizatio n during hydrosilation. Network compositions by elemental analysis tog ether with the low sol fractions indicate efficient crosslinking. Thes e data suggest highly efficient network formation and well-defined bic omponent network structures. While PIE and PDMS showed T-g's at -72 an d -124 degrees C, respectively, the bicomponent network did not exhibi t clearly discernible phase transitions. The heat stability of bicompo nent networks increased slightly with increasing PDMS content showing initial (10%) degradation temperatures at similar to 380 degrees C in nitrogen and similar to 320 degrees C in air. Tensile strengths and el ongations were dependent on composition and varied in the 0.6-3.8 MPa and 600-1100% ranges, respectively. The swelling behavior was not much affected by composition. (C) 1998 John Wiley & Sons, Inc.