Synthesis of monodisperse polymer suspensions with a narrow particle size distribution in the presence of water-insoluble triple block copolymers of polypropylene oxide and polyethylene oxide (pluronics)

The colloidal chemical properties of triple block copolymers of polypropylene oxide and polyethylene oxide (pluronics of various structures) were studied in comparison. All of them are shown to be surfactants but differ in interfacial tension, surface activity, surface area occupied in the adsorption layer, and adsorption layer thickness. The kinetic regularities of polymerization of styrene and methyl methacrylate were studied. The particle diameters and their size distribution were determined. Distinctions in the kinetic regularities of polymerization are shown: the shape of the conversion—time curves (for the duration of the initial and stationary stages of polymerization) and the dependences of the diameter on the surfactant concentration and monomer to water volume ratio. In the presence of the water-insoluble pluronics, the mechanism of formation of polymer—monomer particles and interfacial layer on the surface differs from that when using water-soluble surfactants, which makes it possible to distinguish these processes into an independent type of heterophase polymerization.

     

Influence of the microwave irradiation on the enzymatic activity of trypsin in the presence of poly(N-vinyl amides)

The features of the microwave irradiation effect on trypsin state and changes jn its enzymatic activity in the presence of poly(N-vinyl amides) at various temperatures have been studied. Comparison of the denaturizing effect of the irradiation and of convective heating has revealed, along with the thermal factors, the specific effects of microwave radiation. These effects have been found to affect both protein and polymer molecules, to change their interaction parameters, and thus, to modulate trypsin enzymatic function.     

Amphiphilic Linear-Branched Copolylactides and Disperse Systems on Their Basis

The linear-branched copolylactides containing linear side poly(ethylene oxide) blocks are synthesized and characterized. The critical micelle concentrations and the aggregative stability and the dispersity of oil/water emulsions stabilized by these copolymers are estimated. The polylactide microparticles are obtained by emulsification followed by evaporation of an organic solvent using acetylsalicylic acid as a model drug. The structure of copolylactides strongly affects the properties of the microparticles. On one hand, the presence of large poly(ethylene oxide) blocks in the linear-branched macromolecules leads to the formation of colloidal systems with a higher aggregative stability of emulsions and a lower size of particles, and on the other hand, the microparticles formed from these copolymers possess a lower incorporation efficiency relative to water-soluble low-molecular-mass compounds and the profile of the release of these compounds is nonlinear and contains the region of accelerated release.     

Thermooxidative stabilization of acrylonitrile terpolymers obtained under reversible chain-transfer conditions: Effects of synthesis temperature and initiation method

The terpolymerization of acrylonitrile, methyl acrylate, and itaconic acid mediated by a reversible addition-fragmentation chain transfer agent, dibenzyl trithiocarbonate, and initiated by AIBN at 80°C, potassium persulfate at 45–55°C, and radiolysis at 20°C is studied. In all the cases, polymerization proceeds via the pseudoliving mechanism, which is preserved up to ultimately high monomer conversions (80–90%). According to FTIR ATR and NMR spectroscopy, all the synthesized terpolymers are characterized by close monomer compositions and their degree of branching is too low to be detected spectroscopically. However, the thermal behaviors of terpolymers obtained by polymerizations at various temperatures are different, namely, the lower the temperature of terpolymer synthesis, the slower the thermooxidative stabilization processes occurring in it.