Microporous polymeric composites from bicontinuous microemulsion polymerization using a polymerizable nonionic surfactant

The formation of microstructural polymeric composites by the polymerization of methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), a nonionic macromonomer omega-methoxy poly(ethylene oxide)(40) undecyl-alpha-methacrylate (PEO-R-MA-40) in the bicontinuous microemulsions has been successfully achieved. By photoinitiated polymerization at about 35 degrees C, these microemulsions gelled within 30 min and transparent polymeric composites were formed on further polymerization. Various concentrations of KCNS solution were also used in the microemulsions for monitoring the variation of conductivity during polymerization. Bicontinuous structures of microporous composites were produced when the aqueous solutions in precursor microemulsions contained about 25-60wt%. The pore sizes of these polymeric composites were generally smaller than 100nm in diameter and they exhibited two distinctive glass transition temperatures (T-g) The higher one was about 70 degrees C which was almost unaffected by the KCNS concentration in precursor microemulsions. This higher T-g might derive from the backbone of the copolymers. The lower T-g increased markedly from -52 to -1.8 degrees C as the KCNS concentration increased from 0.05 to 2.5 M. It is attributed to the increasingly restricted motion of long pendant groups (side chains) of hydrophilic PEO-R-MA-40 by forming complexes with KCNS. (C) 1997 Elsevier Science Ltd.