AMPHIPHILIC NETWORKS .11. MECHANICAL-PROPERTIES AND MORPHOLOGY

The bulk properties of two types of amphiphilic networks, poly(2-hydro xyethyl methacrylate)-l-polyisobutylene (PHEMA-l-PIB, H-network) and p oly(N,N-dimethylacrylamide)-l-polyisobutylene (PDMAAm-l-PIB, A-network ), have been investigated. Tensile strengths decreased considerably by swelling, and the decrease was more severe by swelling in water than in n-heptane. Elongations increased by swelling in water; however, the change was not consistent upon swelling in n-heptane. The hardness of dry networks decreased with increasing PIB content, while for wet net works it was similar to dry networks containing 85 wt % PIB. Small-ang le X-ray scattering showed that average interdomain spacings decreased with increasing PIB content. According to dynamic mechanical thermal analysis (DMTA) the glass transition temperatures (T-g) of the respect ive hydrophobic and hydrophilic components shift toward each other wit h increasing PIB content. A ''liquid-liquid transition'' (T-ll) above the T-g of the hydrophilic component was apparent by DMTA, but could n ot be found by differential scanning calorimetry (DSC). (C) 1997 John Wiley & Sons, Inc.