Yoshifumi Yamagata

Change in the two-step flow behavior on aging the ternary mixture comprising monoalkyl cationic surfactant, long-chain alcohol and water II. Analysis of the creep behavior

Abstract A two-step development of the internal structure on aging the ternary mixture comprising cetyltrimethylammonium chloride (C 16 CA), cetyl alcohol (C 16 OH), and water was elucidated from the change in the creep behavior. The system was expressed by a six-element model comprising two Voigt units in series with a Maxwell unit. A similar increase in the instantaneous elastic modulus G 0 , the Newtonian viscosity η 0 , and the elastic modulus and viscosity of the Voigt units ( G 1 , η 1 ) with a longer retardation time τ 1 were observed on aging up to 1–3 days, followed by a leveling off. Conversely, the elastic modulus and viscosity of the Voigt units ( G 2 , η 2 ) with a shorter retardation time τ 2 were constant at the beginning, followed by an increase on aging. From a cryo-SEM observation, we confirm that the two-step development considered from the creep properties on aging was caused by an initial coagulation to form a network of multilamellar vesicles, and a subsequent phase transition from vesicles to lamelae.

Change in the two-step flow behavior on aging the ternary mixture comprising monoalkyl cationic surfactant, long-chain alcohol and water I. Viscous flow preceded by incipient elastic deformation

Abstract Change in the rheological behavior during aging was monitored by the cyclic shearing tests on the ternary system, comprising cetyltrimethylammonium chloride (C16CA), cetyl alcohol (C16OH) and water. In all the stress controlled experiments, typical shear thinning flow was observed at higher shear rate, preceded by an apparent shear thickening behavior below 10−3 s−1. From the relationship between the shear stress τ and the strain γ, however, an elastic deformation was observed at the low-shear region marked by an apparent yield value τa. The apparent viscosity of the ternary mixture increased on aging. The maximum apparent viscosity ηmax increased linearly on aging for 1–3 days, fell discontinuously the decrease in the rate of increase of ηmax. A similar increase and a level off on aging were observed for an apparent elasticity Ea and τa. These elastic properties are related to the development of the initial structure. From these observations, a two-step development of the internal structure was proposed.

Polymer Micelles II. Effects of Alkyl-Chain Length on the Self-Assembly of Copolymers of Acrylic Acid and Alkyl Acrylate in Aqueous Media.

アクリル酸 (AA) とアクリル酸エチル (EA), n-ブチル (BA), またはドデシル (DA) との2元共重合体の水溶液中における会合挙動に及ぼすアルキル鎖長の影響を光散乱, レオロジー, および泡特性によって調べた. 共重合体の水中での見かけ重量平均分子量は, アルキル鎖が長いほど高かった. AA/EAおよびAA/BA共重合体の水溶液は高濃度でも粘性流体であるのに対し, AA/DA共重合体は, 濃度10wt%でゲル的挙動を示した. さらに泡特性解析から, AA/DA共重合体は気-液界面に配向し, 界面活性剤水溶液の泡膜を安定化することがわかった. 以上の結果から, AA/アクリル酸アルキル共重合体においてアルキル鎖長がドデシル基のように長い場合には水中で高度に分子間会合し3次元網目構造を形成し, また, 界面活性剤とも十分に強く会合することが明らかになった.