Nobuo Kawahashi

Micellar properties of a series of octaethyleneglycol-n-alkyl ethers with homogeneous ethylene oxide chain and their temperature dependence

The CMC values of a homologous series of octaethyleneglycol-n-alkyl ethers (CnE8; n = 10 to 15) were determined from the concentration dependence of surface tension in the temperature range from 15.0 to 40.0°C. The free energy change associated with micelle formation, ΔFm, was calculated from the temperature dependence of the CMC. ΔHm and ΔSm values were estimated from the slopes and the intercepts, respectively, of the log CMC versus the reciprocal of temperature plots. Furthermore, the ΔFm values of the surfactant were separated into contributions from the hydrophobic (ΔFm(h)) and hydrophilic groups (ΔFm(−W)). It was found that the ΔFm(h) values were negative, whereas the ΔFm(−W) values were positive. From a plot of ΔFm(−W)/T versus 1/T, the ΔHm(−W) was calculated and amounted to 9.86 kcal/mole. In contrast ΔHm(h) calculated from the difference between ΔHm and ΔHm(−W), was negative. The corresponding value of ΔSm(−W) amounted to 27.9 cal/mole · deg. Likewise, ΔSm(h) was positive. The micellization of these nonionic surfactants is discussed in terms of the separate contributions made by the hydrophilic and the hydrophobic groups.

Copper and copper compounds as coatings onpolystyrene particles and as hollow spheres

Submicron-sized anionic polystyrene latices have been coated with uniform layers of copper compounds by aging dispersions of the polymer colloid in the presence of aqueous solutions of Cu(NO3)2, urea, and poly(N-vinylpyrrolidone) at 85 °C. The thickness and morphology of the deposited layers can be altered by suitable adjustment of the reactant concentrations and the aging time. Hollow colloidal spheres of metallic copper and copper oxide were obtained by calcination of the coated polystyrene latices at elevated temperatures in nitrogen and air, respectively.