Hideomi Matsuda

Temperature dependences of micellar molecular weight and radius of nonionic surface active agent in the aqueous solution

Abstract The molecular weight and diffusion constant of poly(oxyethylene) dodecyl ether (C 12 OE 9·3 ) micelles with an average of 9.3 oxyethylene group were determined from light-scattering measurements and free boundary experiments over a wide temperature range. It was found that micelles formed by C 12 OE 9·3 were monodisperse in the temperature range studied. Plots of the logarithms of micellar molecular weight and micellar radii estimated from the diffusion constants against the temperature have a break point around 45°C. This temperature agrees with a theta point where the second virial coefficient obtained from light-scattering measurements is zero. Although the number of the molecules participating in micelle formation increases with temperature, the size of the micelle remains constant up to the temperature corresponding to the theta point, because the spherical micelle is packed with increasing tightness. The increase in the size and weight beyond that point may be attributed to a departure from spherical shape.

Activation energy for crystallization of low molecular weight poly(ethylene oxide) and low molecular weight poly(ethylene oxide)/poly(methyl methacrylate) blends determined by DSC and polarized optical microscopy☆

Abstract The crystallization process of poly(ethylene oxide) (PEO) and PEO/poly(methyl methacrylate) (PMMA) blends in the low molecular weight region of PEO was studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The half-time of the crystallization t 1 2 , the time at which crystallinity X(t) = 1 2 , was inversely proportional to the linear growth rate G of spherulite, i.e. t 1 2 −1 ∝ G . The value of E characterizes the temperature dependence of the activation energy for the formation of a secondary nucleus on the growing side surface of the crystal lamella and was evaluated from the t 1 2 measured by DSC. The value of E of PEO was not affected by blending PMMA. However, the slightly increasing tendency of E was observed for PEO and PEO/PMMA blends with increasing molecular weight of PEO, M PEO . This tendency may correspond to the crossover of E from low molecular weight material to polymer.

Molecular weight dependence of coexistence curve of polystyrene/Poly(2-chloro styrene) blends

Phase diagrams of polystyrene (PS)/Poly(2-chloro styrene) (P2-ClS) blend systems were determined by differential scanning calorimetry (DSC) measurements in order to investigate the molecular weight dependence. The temperature-concentration region where the two phase state is stable increased with increasing PS molecular weight showing the tendensy to increase the incompatibility.

Flow Birefringence and Viscosity of Highly Concentrated Aqueous Solutions of Non-ionic Surface Active Agents and Their R elation to Inverted-type Micelle

疎水基,ならびにポリオキシエチレン基の重合度を異にする数種の非イオン性界面活性剤を用い,濃度70～90%水溶液の流動複屈折度Δn,ならびに粘度ηの各温度における濃度変化を測定し,逆型ミセル構造との関係について検討した。実験の結果によれば,Δnははじめ正の値を示すが,濃度の増大とともに減少して,界面活性剤の種類,および温度によって定まるある特定の濃度から負の値を示すようになる。また,複屈折度Δnの正負はそのときの溶液の濃度によってきまるが,いずれにしてもその絶対値は温度を上昇すると減少し,ある温度以上で0になることも明らかにされた。ηの濃度依存性についても実験を行なった。結果は, それぞれΔ n の濃度変化にきわめてよく類似した関係を与えた。これらの実験結果は, 非イオン性界面活剤によって形成される逆型ミセルには,負の複屈折度を示す非球形のものと,複屈折現象を示さない球形のものとがあるとの考えにもとづき,詳細に考察された。またこの考えによると,濃度60～70%以上の逆型ミセル領域における溶液構造についての状態図をつくることができるので,これについても,得られた実験の結果をもとに界面活性剤の種類による比較検討を行なった。