THE HYDROLYSIS OF PHOSPHATIDYLCHOLINE BYPHOSPHOLIPASE A2IN MICROEMULSION AS MICROREACTOR

A novel dispersion method comprising a nucleating agent solubilized in a microemulsion, in polymeric matrix

This second part of our paper focuses on structural characterization of the microemulsion for increasing the crystallization rate of polypropylene (PP) through the entrapment of nucleating agent (nucleator) HPN-68, serving as a transport vehicle. Our concept is based on creating an advantage in dispersion capability of the nucleator that is dissolved in a nanoreactor vehicle, compared with its conventional loading as a crystalline powder. The advantage was achieved by solubilizing the HPN-68 in a microemulsion to decrease its size from micro- to nanoscale. The microemulsions were introduced to the target PP using a mixer. By the end of the mixing, when the water phase had evaporated, only the nucleator and the surfactant remained in the matrix. DSC results showed a 24% improvement in nucleation efficiency of PP by this novel method. It was shown that solubilization of the nucleator depends on the water activity in the microemulsion, and the presence of the nucleator opposes formation of the W/O phase. Light scattering, SD-NMR, and SAXS results showed that HPN-68 is accommodated in the water phase and at the interface, and significantly reduces the level of order in the microemulsion. In intermediate water content, a worm-like structure was proposed instead of the classical bicontinuous one. The structure was confirmed by SAXS and SD-NMR analysis. Viscosity measurements revealed structural transitions in the microemulsions.

The effect of structural variation of alcohols on water solubilization in nonionic microemulsions

This article is the first part of a two-part study that exemplifies how to treat the solubilization of water in multicomponent surfactant-based systems. In particular, it aims at clarifying the role of cosurfactants in water solubilization in these systems. The judicious selection of the components in such systems to maximize water solubilization is occasionally thought to be dictated by the chain length compatibility principle, which may be expressed quantitatively by the BSO (Bansal, Shah, O'Connell) equation. Here we demonstrate some limitations of the equation. For example, in our best model system, C12(EO)8/dodecane+pentanol=1:1 (by weight)/water at 27+/-0.2 degrees C, the BSO equation predicts that no alcohol is needed for maximum water solubilization, contrary to our experimental findings. We discuss how to optimize the alcohol/oil weight ratio needed for stabilizing four-component microemulsions. In our model systems C12(EO)8 or C(18:1)(EO)10/pentanol/dodecane/water, this optimal weight ratio is 1:1. We also highlight the difference between the effect of normal alcohols on water solubilization-which passes via a maximum-and their effect on percolation processes and structured changes of proteins, which depends solely upon the alcohol hydrophobicity. For the investigation of the effect of branching on phase behavior the utilization of an extended form of the geometrical branching factor F(b) is suggested. The meaning of this factor is elucidated by comparing it with topological indices.

An index of lipid phase diagrams

There is a growing awareness of the utility of lipid phase behavior data in studies of membrane-related phenomena. Such miscibility information is commonly reported in the form of temperature-composition (T-C) phase diagrams. The current index is a conduit to the relevant literature. It lists lipid phase diagrams, their components and conditions of measurement, and complete bibliographic information. The main focus of the index is on lipids of membrane origin where water is the dispersing medium. However, it also includes records on acylglycerols, fatty acids, cationic lipids, and detergent-containing systems. The miscibility of synthetic and natural lipids with other lipids, with water, and with biomolecules (proteins, nucleic acids, carbohydrates, etc.) and non-biological materials (drugs, anesthetics, organic solvents, etc.) is within the purview of the index. There are 2188 phase diagram records in the index, the bulk (81%) of which refers to binary (two-component) T-C phase diagrams. The remainder is made up of more complex (ternary, quaternary) systems, pressure-T phase diagrams, and other more exotic miscibility studies. The index covers the period from 1965 through to July, 2001.