Using self‐consistent field (SCF) theory, we studied the self‐assembly characteristics of polyurethane pre‐polymer dispersions in aqueous solutions. With a molecularly detailed model implementing the Scheutjens–Fleer discretization scheme, it is shown how the stability, equilibrium size, and internal structure of the (swollen) micelles in polyurethane (PU) dispersions depend on the chemical structure and the molecular composition of the charged pre‐polymer mixtures. The stability region of these micelles is found to increase when acid groups become deprotonated and when the ionic strength is lowered. Insight into the physical–chemical behavior of PU pre‐polymer dispersions is important for the subsequent process of film formation from the PU dispersions for the final coating properties.
To overcome mass transport limitations that are usually encountered on immobilizing highly active catalysts, cationic latex particles were used as support for tetrasodium phthalocyaninatocobalt(I1)tetrasulfonate (2). The cationic latex was prepared by emulsion copolymerization of styrene and divinylbenzene in the presence of a block copolymer from styrene and 4-vinyl-N-methylpyridinium PSqPVP serving as surfactant. The latex-bound system was found to considerably increase the reaction rate of the oxidation of 2-mercaptoethanol in the presence of 2 as compared with the conventional polymer-free system. Michaelis-Menten kinetics was observed for all three systems investigated, that is the block copolymer-stabilized latex system, the homogeneous block copolymer system and the quaternized 4-vinylpyridine homogeneous homopolymer (qPVP) system. Although the stability of the latex and qPW-containing systems after successive runs is rather poor, this immobilization method shows the great potential value of anchoring highly active systems retaining high catalytic activity. The turnover number is increased on immobilizing the block copolymer compared with the homogeneous block copolymer solution. The Michaelis constant is hardly affected by immobilization. Due to conformational changes of the polymer chain on immobilization, a comparison between the latex system and the homogeneous system containing either homopolymer or block copolymer remains difficult. 0 1990, HUthig & Wepf Verlag, Basel CCC 0025-1 16X/90/$03.00
In this paper we report the determination of partitioning of coalescing agents (organic co-solvents) in water-borne latex emulsions by means of a fluorescence method. An environment-sensitive fluorescent probe was copolymerized via emulsion polymerization. The presence of organic co-solvents inside the polymer particles is revealed by the photophysical properties of the probe. In particular, the position of the fluorescence emission maximum of co-polymerized can be used to measure the amount of coalescing agent present in the polymer particles. The spectral shifts are shown to be due to the softening of the matrix, rather than to solvation of the probe by the added co-solvent.
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