PHASE-SEPARATION IN SILICA SOL-GEL SYSTEM CONTAINING POLYACRYLIC-ACID .2. EFFECTS OF MOLECULAR-WEIGHT AND TEMPERATURE

Effects of molecular weight of coexisting polyacrylic acid (HPAA) and reaction temperature on phase separation and gelation behaviors were studied for acid-catalyzed, alkoxy-derived silica systems. The range of concentrations of HPAA which resulted in interconnected porous morphologies decreased and shifted toward lower concentrations as the molecular weight increased. The concentration range became larger with increasing reaction temperature. In addition to the relation between rates of phase separation and polymerization, viscosities of gelling silica network and pore-filling liquid during the domain formation process were responsible for the size and connectivity of resultant domains.