In order to investigate the partition of initiators for quasi-static precipitation polymerization of acrylamide(AAm) and methacrylic acid(MAc) in ethanol, azo-initiators were employed with various functional groups such as ―COOCH3(V-601, dimethyl 2,2′-azobis(isobutyrate)), ― CN(V-65, 2,2′-Azobis(2,4-diemthylvaleronitrile)), ― COOH(V-501, 4,4′-azobis(4-cyanovaleric acid)) and ―NH-(VA-061, 2,2′-azobis[2-(2-imidazolin-2-yl)propane]), respectively. Particle size, induction time and kinetics of polymerization were investigated by the scanning electron microscopy(SEM) and gravimetry. It was observed that the polymerization parameters, such as the particle size, induction time and polymerization rate, were considerably affected by the functional groups of initiators. Besides, the monomer concentration also played important roles in the particle formation. By using V-601, the polymerization rate was strongly correlated with the total surface area of particles and the concentration of initiators. However, by using V-501, the polymerization rate was strongly related to W0 Ci,0, where W0 is the initial concentration of monomers and Ci,0, the initial concentration of initiators. The results indicated that the different functional groups determined the different partition types of initiators between the minimonomer droplets and the continuous phase due to the molecular interactions of initiator and monomers. V-601 was all partitioned in the continuous phase, but a part of V-65 was partitioned in the minimonomer droplets. Besides the V-501 dissolved in the continuous phase, a part of V-501 was adsorbed on the surface of minimonomer droplets. VA-061 destroyed the stability of minimonomer droplets by the formation of zwitterions with MAA.
ATRP-template dispersion polymerization of methacrylic acid(MAA) on the template of polyvinyl pyrrolidone(PVP K-30) was carried out in the aqueous solution by using methyl 2-bromopropionate(MBP)/CuCl/2,2?-bipyridine(bpy) as the initiation system. The scanning electron microscopy(SEM), dynamic light scattering(DLS) and gel permeation chromatography(GPC) were employed for evaluating the results of polymerization. As a result, the minimonomer droplets formed due to the H-bond interaction of PVP-MAA. The stability of droplets was dependent on pH and the concentrations of both PVP and MAA. When pH < 2, the coagulum of PVP-MAA formed, whereas when pH > 4.5, the droplets were not observable by DLS. In order to prepare the stable latex, the concentration of PVP should be lower than 9 wt%, whilst the concentration of MAA should be lower than 5.5 wt%. The optimum condition was pH 2.4, PVP 4.76 wt% and MAA 5 wt%, by which the stable latex of ca. 50 nm nanoparticles of PMAA/PVP was prepared by ATRP polymerization and simultaneously the molar mass of PVP was duplicated by PMAA according to GPC diagrams. In contrast, by using AIBN, KPS and KPS-Na2SO3 redox initiation system, the coagulum accompanying with the larger molar mass of PMAA was obtained, irrespective of pH and concentrations of PVP and MAA.
