The mechanism for the formation of micron‐size polymer particles in the dispersion polymerization of methyl methacrylate was investigated by applying dynamic light scattering to monitor the evolution of the average particle size in the early stages of the polymerization. In addition, the contributions of physically adsorbed stabilizer and graft copolymer were evaluated by measuring the bound, unbound (adsorbed), and free stabilizer, and by determining the amount of added stabilizer required in seeded dispersion polymerizations. Twenty nanometer particles (termed nuclei) were the smallest particles detected and are considered to be formed by aggregation of growing polymer chains precipitating from solution as they exceed their critical chain length. Aggregation of these nuclei with themselves and their aggregates continues until mature and stable particles are formed. This occurs when sufficient stabilizer occupies the particle surface which includes both the polymeric stabilizer [poly(vinylpyrrolidone)] and its graft copolymer which is created in situ. The effects of process variables are discussed based on this mechanistic picture of the dispersion polymerization process. © 1994 John Wiley & Sons, Inc.

Poly(methyl methacrylate) (PMMA) particles ranging in diameter from 2 to 10 μm were prepared by dispersion polymerization. The effects of various polymerization parameters on the size and monodispersity were systematically investigated. The particle size was found to increase with increasing polymerization temperature, concentration and decomposition rate of the initiator, and solvency of the dispersion medium. It also increased with increasing concentration and molecular weight of the polymeric stabilizer, poly(vinyl pyrrolidone) (PVP). As the monomer concentration was increased from 5 to 20 wt %, a minimum was found in the particle size at a monomer concentration of 10 wt %. A costabilizer was found to be necessary for preparing monodisperse particles at stabilizer concentrations below 2 wt %. A recycling experiment showed that the consumption of PVP was quite small in each cycle and the residual materials in this system could be reused readily. © 1993 John Wiley & Sons, Inc.

We demonstrate a facile and rapid in situ partial oxidation synthetic strategy for the fabrication of a mixed valence state Ce-MOF (MVCM) which exhibits intrinsic oxidase-like activity. Furthermore, on the basis of the excellent catalytic activity of the MCVM, a colorimetric approach for the high-throughput detection of biothiols in serum samples was established.

No abstract