Tsunehiko Kuwamura

Anionic surfactants with divalent gegenions of separate electric charge: solubility and micelle formation

In order to clarify the relationships among solubility, micelle formation, and Krafft point, anionic surfactants with three types of divalent gegenions were prepared and their micelle formation and solubility examined. The first gegenion type was characterised by localized charge(divalent metal ion), the second by diffuse charged,(1,1′-dimethyl-[4,4′] bipyridinium ion or methylviologen ion), and the last by separate charged,(l,1′-alkanediyl-bis-pyridinium ion). The effects of the unlocalized gegenions were compared with those of the localized gegenions, and the following conclusions could be drawn from the experimental results: (i) the crystalline state with gegenion of diffuse or separate charge is less stable energetically and has higher solubility, and (ii) the difference in cmc value among the three types of surfactants is relatively small when the charge separation is small, but a large charge separation gives rise to marked decrease in cmc value suggesting that the alkylchain of separate gegenion folds and penetrates the inner hydrophobic part of the micelle. Also we observed that surfactants with more water of crystallization are easier to dissolve with a smaller enthalpy change of dissolution.

Heat of micelle formation: Effect of counterions with concentrated, diffused, and separated electric charges

Heats of micelle formation were estimated from calorimetric measurements of anionic surfactants to see if there is any effect of the electrical charge of the counterion on micelle formation from the viewpoint of enthalpy change. The cationic counterions used are Na+ and Cu2+ for the concentrated electric charge, MV2+ for the diffused and 1,1′-(1,ω)-alkanediyl)bispyridiniumionsn=2, 4, 6, 8, 10, 12, 14 for the separated. The heat of micelle formation was obtained by subtracting an enthalpy change of dissolution of surfactant solid precipitated below the micelle temperature range (MTR or Krafft point) from a heat of complete dissolution of the precipitated surfactant solid around the MTR. The heats thus evaluated were found to be much more temperature-dependent than counterion-dependent. They were compared with the enthalpy change calculated from the CMC change with temperature, and the big difference between them was discussed from a thermodynamic point of view.

Surface active block copolymers: I. The preparation and some surface active properties of block copolymers of tetrahydrofuran and ethylene oxide

A new type of surface active block copolymer (TE type) having the general formula HO(C2H4O)x(CH2. CH2CH2CH2O)y-(C2H4O)zH, was obtained by addition of ethylene oxide to polyoxytetramethylene glycols with molecular weight of 1000-3400. TE types in which the polyoxyethylene sections comprised more than 20–25% of the total weight are soluble in water, and the relation between cloud point and oxyethylene content for TE types was similar to that for propylene oxide-ethylene oxide block copolymers (Pluronics). Some surface active properties of TE types were examined in comparison with those of Pluronics and some other surfactants. The surface tension, foaming and antifoaming properties of TE types were comparable to those of Pluronics. Although the wetting power of TE types was poor, their suspending power (for carbon black) was superior to that of Pluronics in both aqueous and nonaqeuous media. The addition of TE types to some conventional detergents enhanced significantly their detergency. TE types showed a remarkable demulsifying action, on addition to some W/O emulsions.

Coagulation behavior of vesicles composed of crown ethers and phospholipids caused by bolaform surfactants

Abstract The colloid stability of mixed vesicles composed of two components, a crown ether with a long hydrocarbon chain and a phospholipid, against bolaform surfactants was studied. The critical coagulation concentration of primary ammonium ions of the bolaform for the vesicle is lower than that of corresponding quaternary ammonium ions, which can be attributed to the affinity difference between the two types of terminal ionic groups for the crown ether. The steric bulky effect of bolaform ions on the screening potentiality against the surface charges is negligible, but the hydrophobic interaction of a hydrocarbon chain connecting the two terminal ionic parts of the surfactants with the vesicle surface plays a significant role in the vesicle coagulation.

Syntheses of 1-Poly (oxyethylene) pyridinium-2-dodecanoylimines and their Properties

A series of 1-poly (oxyethylene) pyridinium-2-dodecanoylimines (3) were synthesized in a good yield from 2-aminopyridine and poly (oxyethylene) (POE) monochlorides ranging in oxyethylene number (n) from 1 to 5. Some properties of (3) were examined and compared with those of 1-methylpyridinium-2-octanoylimine (4) and dodecyl POE ethers (5). (3) with n≤3 were more soluble in water than (4) and their specific cloud point increased with increasing the number of n. The surface tension reduction of (3) was similar to that of (4). The cmc value of (3) was about one-hundredth of that of (4) but similar to that of (5). From the relationship of (Fig.-1) between cloud point and n of (3) and (5), it was estimated that the hydrophilic effect of the pyridinium-2-imine group in (3) corresponded to that of two or three oxyethylene units in (5). On the basis of IR spectra and the aqueous properties of (3), it was concluded that the contribution of the dipolar ionic form of (3) was strong especially in an aqueous environment.