Bruno Vuano

Triangular phase diagram of the catanionic system dodecyltrimethylammonium bromide-disodium dodecanephosphonate-water

Abstract The catanionic system dodecyltrimethylammonium bromide (DTAB)–disodium dodecanephosphonate (DSDP)–water phase behaviour differs from that shown by other catanionic systems (e.g. low solubility, highly non-ideal interactions in micelles, formation of lamellar mesophases and vesicles and/or liposomes, strong reduction of the critical micelle concentration (CMC) and the domains of existence of micelles). The system is highly soluble at all DTAB:DSDP ratios. The CMC has an almost ideal dependence on the DTAB:DSDP ratio. There is a wide domain of existence of spherical micelles, followed by a much largest domain of existence of rodlike micelles. At high concentration, only hexagonal liquid crystal exist. No vesicles nor lamellar mesophase were found. An explanation of this behaviour is proposed, based on steric effects due to the size of the headgroups.

The aggregation ofn-dodecanephosphonic acid in water

Several techniques were employed to study the aggregation ofn-Dodecanephosphonic Acid (DPA) in water. At 22°C, the solubillity of DPA increases, probably due to the formation of small premicellar aggregates. The CMC is (5.4±2.4) ×10−4 mol·dm−3 and the solubility reaches the CMC value at 26°C. At 30°C and at a concentration of about 9×10−3 mol·dm−3, a lamellar mesophase appears. Both micelles and liquid crystal lamellae are almost uncharged. Their polar heads have strong hydrogen bonds between them. The ionization of DPA molecules in micelles and mesophase structures is strongly reduced in comparison with monomerically dissolved molecules.

The aggregation of aqueous dodecylphosphonic acid in dodecyltrimethylammonium hydroxide mixtures

The aggregation of aqueous dodecylphosphonic acid (DPA) and dodecyltrimethylammonium hydroxide (DTAOH) mixtures was studied by several methods. The behavior of DPA-rich mixtures is close to that of pure DPA. This is probably due to the preservation of the hydrogen-bonded structure of the micellar headgroup layer. The behavior is almost ideal. BetweenyDPA=0.5 and 0.33 (yDPA being the mole fraction of DPA in the surfactant mixture), the hydrogen-bonded structure of the micellar headgroup layer is destroyed. A sort of “micellar azeotrope” is formed, and the maximum of non-ideal interaction between the two surfactants is attained atyDPA=0.4. ForyDPA<0.33 the system behaves as a common mixture of a cationic surfactant and a non-ionic one (DPA.2LTA). There is a phenomenon of counterion “condensation” on aggregates at concentrations over the CMC.

Studies on styrene phosphonic acid

Some properties of styrene phosphonic acid (SPA) were studied. The crystals were triclinic, witha=0.6434 nm,b=0.5842 nm,c=2.0338 nm, α=96.17°, β=97.33°, γ=79.65° andZ=4. SPA underwent a change in crystal structure at 78.8°C, the hydrocarbon network became disordered (“liquid-like”) at 138.5°C. Crystals melted at 148.6°C giving a cubic mesophase, then changed to an isotropic liquid at 155.6°C and at 162.13°C SPA underwent decomposition. Values for pK1=2.15 and pK2=7.66 were obtained at 25°C. The water solubility of SPA at several temperatures, and its interaction with surfactant micelles were determined.

Inversion Properties of n-Alkane Phosphonic Acids Stabilized Emulsions: HLB Dependence

The emulsifier properties of n-alkane phosphonic acids (C10H21PO3H2; C12H25PO3H2 and C13H27PO3H2) and their mono- and di-sodic salts were studied, with emphasis on the morphological and dynamical inversion properties as a function of their neutralization degree. Maximum stabilization properties were appreciated for C10PO3H2 and C12PO3H2 while not for C13PO3H2. Such fact is associated to their odd number of carbon atoms chain, which is the origin of the intrachain constraints on the tail-chain flexibility.

Thermal reaction of cinnamic acid and of β-styrylphosphonic acid with urea

The thermal reaction of b-styrylphosphonic acid under experimental conditions similar to those applied to cinnamic acid and to methyl cinnamate to provide 6-phenyl-5,6-dihydrouracil, led to the formation of the novel 6-phenyl-5,6-dihydro-4-phosphorylamide-(1H,3H)-2-pyrimidinone.

A Serendipitous Extension for Illustrating Newman Projections

The idea of using overhead Newman projections for understanding conformational analysis was extended, making possible the construction of an inexpensive, very simple hand-pocket model from two transparencies of about 100 cm2, a small piece of chalk, and two thumbtacks.