Preparation Of Transparent Microporous MMA-BA Copolymer Materials From Microemulsion Polymerization

Microemulsions are transparent thermodynamically stable dispersions made with water and oil in the presence of surfactant. Increasing attention has been payed to the preparation of microporous materials by inverse and bicontinuous microemulsion polymerization. In this dissertation, the preparation of transparent microporous copolymer materials by microemulsion polymerization of MMA-BA was studied systematically, and the kinetics of polymerization in inverse microemulsion percolating system was investigated. First, the phase behavior of microemulsion was studied and the pseudo-ternary phase diagrams composed with MMA-BA/coemulsifier/SDS-H2O were figured out. The results showed that when SDS was chosen as emulsifier, both AA and n-pentanol could be used as coemulsifier to form stable one-phase microemulsions. Apparent percolation of conductivity was observed during the phase transformation of microemulsion, wherein percolation thresholds varied with the types and contents of coemulsifier in initial systems. n-Pentanol had a baffling effect on the percolation behavior while AA had a promoting effect. It was also seen from the two pseudo-ternary phase diagrams that a larger region of transparent one-phase microemulsion could form with AA as coemulsifier, and lamellar liquid crystal appeared during the phase transformation of microemulsion with n-pentanol as coemulsifier.According to phase-diagram, inverse microemulsion percolating systems and bicontinuous microemulsions were prepared for polymerization. The selection of proper initiator was the onset of searching for stable polymerization conditions. It was found that serious phase separation occurred during the polymerization of microemulsions with n-pentanol as coemulsifier. The microemulsion, however, could polymerize stably with AA as coemulsifier. As to the microemulsions consisting of MMA-BA/AA/SDS-H2O, transparent copolymers could be obtained with AIBN as initiator from inverse microemulsion percolating system after polymerization for 3h at 55℃. However, KMnO4-H2C2O4 redox system was mostappropriate for initiating bicontinuous microemulsion polymerization to prepare transparent polymer gels, which could be formed even in 10min at 45℃.The kinetics of polymerization initiated by AIBN in percolating microemulsion composed of MMA-BA/AA/SDS/H2O was studied. The influence of initiator concentration, emulsifier concentration, coemulsifier concentration, mass fraction of aqueous phase and reaction temperature on polymerization rate at 5% conversion was investigated, and the following relation was obtained.dC/dt∝[AIBN]0.89[SDS]-0.5[AA]1.3[W]0.16The exponent expressing dependence on initiator was 0.89, which meant that monoradical termination was perhaps the main termination manner. The negative exponent expressing dependence on emulsifier concentration was attributed to the transfer reaction of macromolecular radicals to emulsifier. The function of AA in microemulsion polymerization was remarkable due to its highly efficient co-emulsification and bridge copolymerization to join oil phase together with aqueous phase. In addition, microemulsion polymerization was sensitive to temperature. The apparent energy of activation was 114kJ/mol.Based on stable polymerization, the influence of aqueous phase concentration, coemulsifier concentration, initiator concentration, and crosslinking agent concentration on the microporous morphology of the obtained copolymer materials was discussed by ESEM and TGA. The results showed that there was a certain correspondence in morphology between precursor microemulsions and final copolymers. Inverse microemulsion percolating systems yielded polymer materials with a closed-cell porous structure, and some of the holes began to crack and connect. Open-cell porous copolymer gels were obtained by the polymerization of microemulsions with a bicontinuous structure. In addition, phase separation occurred during polymerization and post-treatment such as drying process. At the end of this dissertation, some suggest...