The phase behavior of aqueous mixtures of the "clouding" polymer ethyl(hydroxyethyl)cellulose (EHEC) mixed with colloidal particles and surfactants has been studied. These types of mixtures are important in many technical formulations. Two types of particles, polystyrene latex and silica, and two types of EHEC, nonmodified EHEC (N-EHEC) and hydrophobically modified EHEC (HM-EHEC), were studied. The EHECs adsorb to both kinds of particles. Both the amount and the type of added surfactant were seen to dramatically influence the partitioning of the particles between the EHEC-rich and EHEC-poor phases of phase-separated mixtures (above the cloud point temperature). Surfactants that are known not to associate with the EHEC backbone, that is, nonionic surfactants and short-chain cationic surfactants, changed the interaction between EHEC and the colloidal particles from attraction to repulsion above a specific surfactant concentration, resulting in a change in the partitioning of the particles from the EHEC-rich to the EHEC-poor phase. No such particle inversion was observed for ionic surfactants that bind to the EHEC backbone. An analysis considering both the binding of surfactant to EHEC and the competitive adsorption of surfactant to the particle surfaces could rationalize all observations, including the large variations observed, among the studied mixtures, in the surfactant concentration required for particle inversion.

Polymer-particle interactions can cause particle flocculation and phase separation problems in waterborne coatings. The problems can be the result of interactions that are either too weak or too strong. It is known by empirical work that addition of surfactants can minimize these problems. In this study, the authors have investigated how different types of surfactants influence the polymer-particle interactions. Both hydrophobic and hydrophilic particles were included in the study, and nonionic, anionic, and cationic surfactants were used. A simple model is suggested that can be used to predict the surfactant concentration needed to stabilize the system. The model considers the cmc (critical micelle concentration) of the surfactant, the adsorption to the polymer, and the adsorption to the particles.

The method of gelcasting requires making a mixture of a slurry of ceramic powder in a solution of organic monomers and casting it in a mold. Gelcasting is different from injection molding in that it separates mold filling from setting during conversion of the ceramic slurry to a formed green part. In this work, nuclear magnetic resonance (NMR) spectroscopy and imaging has been used for in-situ monitoring of the gelation process and gelcasting of alumina. 1H N M R spectra and images are obtained during polymerization of a mixture of soluble reactive acrylamide monomers. Polymerization was initiated by adding an initiator and an accelerator to form long-chain, cross-linked polymers. Multidimensional NMR imaging was utilized for in-situ monitoring of the process and for verification of homogeneous polymerization. Comparison of the modeled intensities with acquired images shows a direct extraction of T1 data from the images.