Preparation of Cross-Linked Monodisperse Poly(acrylic acid) Particles by Precipitation Polymerization.

Water-soluble polymers such as poly(acrylic acid) (PAA) are widely applied in dispersants, thickeners, flocculants, and superabsorbent polymers. Here, submicrometer-sized monodisperse PAA particles were successfully prepared by precipitation polymerization in acetonitrile at 55 °C with 2,2'-azobis(2,4-dimethylvaleronitrile) as an initiator. In a medium with a high dielectric constant, the particles were stabilized by electrostatic repulsion without a colloidal stabilizer during the polymerization.

Mild hypothermia promotes the viability of in vitro-produced bovine blastocysts and their transcriptional expression of the cold-inducible transcription factor Rbm3 during in vitro culture.

In this study, we evaluated the effects of holding in vitro-produced bovine blastocysts under mild hypothermia (33°C or 35°C), by examining viability and hatching rates of day 7 blastocysts (day 0: in vitro fertilization) cultured for 6 days and transcriptional expression of cold-inducible transcription factors Cirp and Rbm3, implicated in mild hypothermia-induced cellular protection against various types of stress. In the normothermic control (38.5°C), viability of the embryos decreased rapidly after day 10, and most samples were degenerated on day 13.

Multicompartment micelle morphology evolution in degradable miktoarm star terpolymers.

Multicompartment micelles with segmented wormlike structures consisting of alternating poly(ethylethylene) (PEE) and poly(gamma-methyl-epsilon-caprolactone) (PMCL) layers were formed upon dispersing samples of micro-[PEE][poly(ethylene oxide)][PMCL] (micro-EOC) miktoarm star block terpolymers in neutral water. Subjecting these dispersions to a pH 12 aqueous buffer at 50 degrees C led to the hydrolytic degradation of the PMCL chains. After 4 weeks, the majority of the micro-EOC molecules were degraded into PEE-b-poly(ethylene oxide) (EO) diblocks and PMCL homopolymers.

Effect of molecular weight on the morphology of polystyrene/poly(methyl methacrylate) composite particles prepared by the solvent evaporation method.

The effect of molecular weight on the morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles was investigated. PS/PMMA composite particles with different molecular weights (M*=MwPS+MwPMMA)/2 approximately 2x10(4)-1x10(6) g.mol(-1)) were prepared by the release of toluene (T) from PS/PMMA/T (1/1/24, w/w/w) droplets dispersed in an aqueous solution of polyoxyethylene nonylphenyl ether nonionic surfactant (Emulgen 911).

Preparation of micrometer-sized, monodisperse "janus" composite polymer particles having temperature-sensitive polymer brushes at half of the surface by seeded atom transfer radical polymerization.

Micrometer-sized, monodisperse polystyrene (PS)/poly[methyl methacrylate-(chloromethyl)styrene] [P(MMA-CMS)] composite particles having hemispherical structure were prepared by solvent evaporation from toluene droplets containing dissolved PS and P(MMA-CMS) dispersed in aqueous solution, which had been prepared using the membrane method. The formation of hemispherical ("Janus") morphology by phase separation between the PS and the P(MMA-CMS) was confirmed by both optical and electron microscopy. Atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate (DM) was subsequently carried out in the presence of hemispherical PS/P(MMA-CMS) composite particles in an aqueous dispersed system.

Formation of "snowmanlike" polystyrene/poly(methyl methacrylate)/toluene droplets dispersed in an aqueous solution of a nonionic surfactant at thermodynamic equilibrium.

"Snowmanlike" polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles were prepared by evaporation of toluene from PS/PMMA/toluene droplets dispersed in an aqueous solution of polyoxyethylene nonylphenyl ether surfactant (Emulgen 911). Partitioning experiments revealed that the Emulgen 911 concentration was higher in the droplets than in the aqueous solution during toluene evaporation. As a consequence, the interfacial tensions between the polymer phases (PS and PMMA) and the aqueous phase (gammaP-T/W) were extraordinarily low (approximately 10(-1) mN/m).

Effect of stabilizer on formation of "onionlike" multilayered polystyrene-block-poly(methyl methacrylate) particles.

The effect of the kind of stabilizers on the formation of "onionlike" multilayered polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) particles was studied. The release of toluene from PS-b-PMMA/toluene droplets dispersed in aqueous medium resulted in the formation of onionlike multilayered structures in the particles for all stabilizers used. However, the surface composition of the particles was strongly affected by the kind of stabilizer.

Revisiting the morphology development of solvent-swollen composite polymer particles at thermodynamic equilibrium.

Morphology of polystyrene (PS)/poly(methyl methacrylate) (PMMA)/toluene droplets, in which phase separation proceeds, dispersed in SDS aqueous solution was examined. It changed from ex-centered PS-core/PMMA-shell to hemisphere with increasing SDS concentration. At low polymer weight fraction (wp), PS and PMMA phases contained non-negligible amount of PMMA and PS, respectively.

Effect of colloidal stabilizer on the shape of polystyrene/poly(methyl methacrylate) composite particles prepared in aqueous medium by the solvent evaporation method.

Effects of the kind and concentration of stabilizers on the nonspherical shape of polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles prepared by release of toluene from PS/PMMA/toluene droplets dispersed in stabilizer aqueous solution were examined. In the case of poly(vinyl alcohol), the surfaces of the obtained particles always had a single dimple. In the case of sodium dodecyl sulfate (SDS), the shapes of the composite particles changed from the dimple, via acorn, to spherical with increasing SDS concentration.

Design and synthesis of Mg2+-selective fluoroionophores based on a coumarin derivative and application for Mg2+ measurement in a living cell.

Novel Mg2+ fluorescent molecular probes (KMG-20-AM and KMG-27-AM; where AM is an acetoxymethyl group) based on a coumarin possessing a charged beta-diketone structure were designed and synthesized. These fluorescent probes produced a red shift from 425 to 445 nm in the absorption spectra after formation of a complex with Mg2+. The fluorescence spectra of these probes also showed a red shift from 485 to 495 nm and an increasing fluorescence intensity after formation of a complex with Mg2+.