פרסומים

We develop a mesoscopic density functional theory (DFT)-based Monte-Carlo approach for studying the phase behaviour of multi-component systems comprised of irreversibly bonded, conventional macromolecules and supramolecular entities. The latter can reversibly associate with each other and the conventional components to ‘‘living’’, equilibrium polymers. The computational approach can be applied to a broad class of supramolecular systems and we focus here on quasi-block copolymer systems that contain conventional, ‘‘dead’’ AB-copolymers with a supramolecular B-terminus and supramolecular B-units. The simulations show that, by properly selecting the architecture of the ‘‘dead’’ copolymers and by varying the supramolecular association constant and the incompatibility between the segment species, A and B, one obtains a variety of different microphase-separated morphologies and macrophase separations. Two representative phase diagrams are reported as a function of the association constant, E(b), and the Flory-Huggins parameter, chi, quantifying the repulsion between A and B segments. The simulation results are qualitatively rationalised by considering the dependence of the stoichiometry on the system’s parameters, and fractionation effects between coexisting phases are illustrated.

Spatially uniform electric fields have been used to induce instabilities in liquids and polymers, and to orient and deform ordered phases of block-copolymers. Here we discuss the demixing phase transition occurring in liquid mixtures when they are subject to spatially nonuniform fields. Above the critical value of potential, a phase-separation transition occurs, and two coexisting phases appear separated by a sharp interface. Analytical and numerical composition profiles are given, and the interface location as a function of charge or voltage is found. The possible influence of demixing on the stability of suspensions and on inter-colloid interaction is discussed. ©2009 The Physical Society of Japan

The use of phospholipids (PL) as surfactants in micellar systems and microemulsions offers many advantages as drug delivery vehicles. PL are commonly used in combination with other non-food surfactants with cosolvents and cosurfactants to form a cascade of delivery structures. The authors incorporated phosphatidylcholine (PC) in a unique U-type water-dilutable phase diagrams exhibiting large isotropic regions of nanostructures. The nanometric liq. structures were prepd. from food-grade emulsifiers. The authors formed water-free concs. with PC that are fully dild. with water to form a variety of unusually structured nanodroplets. Due to the uniqueness of their compn., the designed concs. derived from the nature of the oil phase, type of surfactants, and cosurfactants were characterized and found to be direct micelles (rather than inverse micelles), with the surfactant headgroups convexed toward the hydrophilic phase away from the micelle's core, even in the absence of water. The concs. tend to self-assemble upon adding water to form O/W microemulsions even with small amts. of water (water-poor compns. of 0-20% water). Upon further diln. with water the swollen micelles retain the oil as the inner phase. Multi-component compns. with two types of hydrophilic surfactants were investigated. The most significant enhancement in the total isotropic region was obtained by decreasing the triacetin and PC content in the system. The authors explored, by varying the nature of the headgroups and the nature and length of the lipidic (lipophilic) tails of the PL, the diln. capabilities of each of the systems. [on SciFinder(R)]

The deposition and characterisation of Langmuir-Blodgett (LB) layers of polyaniline (PAN) on solid supports is described. Langmuir films were spread as a mixture of PAN and dodecylbenzenesulfonic acid (DBSA) at the water/air interface and deposited on either glass or indium tin oxide (ITO). Mono- and multi-layer films of PAN/DBSA were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), absorption spectroscopy and cyclic voltammetry (CV). The ultrathin films produced were found to be highly uniform and very stable. Further characterisation of the films was accomplished by scanning electrochemical microscopy (SECM) in the feedback mode. It was found that the conductivity depended strongly on the pH of the solution and the number of layers deposited. Values for the pH-dependent lateral conductivity of PAN LB films are reported.[on SciFinder (R)]

The deposition and characterization of Langmuir-Blodgett (LB) layers of polyaniline (PAN) on solid supports is described. Langmuir films were spread as a mixt. of PAN and dodecylbenzenesulfonic acid (DBSA) at the water/air interface and deposited on either glass or indium tin oxide (ITO). Mono- and multi-layer films of PAN/DBSA were characterized by XPS, at. force microscopy (AFM), absorption spectroscopy and cyclic voltammetry (CV). The ultrathin films produced are highly uniform and very stable. Further characterization of the films was accomplished by scanning electrochem. microscopy (SECM) in the feedback mode. The cond. depended strongly on the pH of the soln. and the no. of layers deposited. Values for the pH-dependent lateral cond. of PAN LB films are reported. [on SciFinder(R)]