Inverse Microemulsion Polymerization Of Methyl Methacrylate

Microemulsions are thermodynamically stable, isotropic, optically transparent dispersions made up of two liquids, incompatible with each other, stabilized by surfactants and cosurfactants. Recently, increasing attention has been paid to the preparation of porous materials by microemulsion polymerization. In this thesis, the kinetics of polymerization in methyl methacrylate(MMA)/acrylic acid(AA)/sodium dodecyl sulfate(SDS)/H₂O and MMA/AA/H₂O inverse microemulsions were studied on the basis of investigation of microemulsion characteristics. The process of microemulsion polymerization was monitored, and the porous polymer materials from microemulsions were analyzed. (1) The phase diagrams of MMA/AA/SDS-H₂O system and MMA/AA/H₂O system were described by visual method and conductivity. The variation in structure of microemulsion was measured by conductometer, viscosimeter and refractometer, respectively. The results showed that the conductivity, viscosity and refractive index of microemulsion changed with increasing the aqueous phase when the amount of MMA/AA mixed monomers was fixed, and indicated that the system changed from W/O microemulsion through bicontinuous microemulsion to O/W microemulsion. The particle analysis showed that the particles were regarded as swollen micelles with reason in O/W microemulsion with low amount of oil phase, the particle size was enlarged with increasing the amount of SDS aqueous solution in W/O microemulsions, and the particles in MMA/AA/H₂O soap-free inverse microemulsions were obviously larger than those in MMA/AA/SDS/H₂O inverse microemulsions. (2) Based on the pseudo-ternary phase diagram of MMA/AA/SDS-H₂O system, the polymerization in inverse microemulsions was initiated with AIBN. The effects of the amount of AIBN, AA and SDS aqueous solution and reaction temperature on the polymerization rate at beginning were investigated. The following kinetic relation was obtained: dC/dt∝[AIBN]^0.8[AA]^1.2[W₁]^0.7 And moreover, the inverse microemulsion polymerization was sensitive to temperature. The apparent total active energy of polymerization was 93.8kJ/mol. (3) Based on the ternary phase diagram of MMA/AA/H₂O system, the soap-free inverse microemulsion polymerization was initiated with AIBN. The effects of the amount of AIBN, AA and water on the polymerization rate at beginning were studied. The following kinetic relation was obtained: dC/dt∝[AIBN]1.0[AA]1.7 The formula dC/dt∝[AIBN]1.0 meant that monoradical termination was perhaps the primary termination manner. In addition, there appeared a maximum of polymerization rate with the water content increasing. (4) The microemulsion polymerization was monitored by refractometer, conductometer and time-resolved light scattering device, respectively. The results showed that the refractive index, conductivity or intensity distribution of scattering light changed along with polymerization and corresponded to different processes of microemulsion polymerization. (5) Based on stable polymerization, the products from inverse microemulsions were analyzed with fourier transform infrared spectroscopy, environmental scanning electron microscope and thermogravimetry. The composition and structure of products from microemulsions whether with SDS or not were found almost same. The products from inverse microemulsions showed closed-cell porous structure and there was a certain correspondence in morphology between precursor microemulsions and end products. Furthermore, the porous morphology of products from MMA/AA/SDS/ H2O inverse microemulsions were more uniform than those from MMA/AA/H2O soap-free microemulsions, and the product treatment methods affected obviously on microporous structure. In addition, the swellability of products in solutions with various pH values were measured. (6) Finally, some suggestions were put forward on the further study of porous polymer materials from microemulsions.