Solutions of different polymers in the same solvent are incompatible as a rule and show phase separation when they are mixed. If incompatibility is also to be observed in systems where one of the polymer components is replaced by colloidal particles, sterically stabilized by a cover of polymer chains, will be discussed in this lecture. After a discussion of the applicability of statistical thermodynamical criteria for colloid stability we focus attention on the potential of average force between two particles, V(r), and the second virial coefficient, B2. First it is shown from general arguments that V(r) and B2 always decrease in magnitude upon addition of particles identical to the particle pair considered. The decrease is particularly large for high molecular weight polymers. Subsequently, the analysis is extended, with the help of simple models, to mixtures of polymer colloid and polymer. It is predicted that B2 should decrease and may become negative when the molecular weight and concentration of the polymer are sufficiently large. For high molecular weight polymer this is of the order of a per cent or less. More polymer is needed for low molecular weights. The destabilization is intimately connected with the expulsion of polymer from the interstitial spaces between approaching particles because of “volume restriction”- and “osmotic” effects. The predictions are in accordance with some experiments that were available. Finally the applicability of light scattering as an experimental tool in these stability problems is stressed. Results are also given of the incompatibility of two polymers in a single solvent in which one of the polymers is masked i.e. does not scatter light.

/pdf/polymers-at-interfaces-and-the-interactions-in-colloidal-1p2p616pc1.pdf

Polymers at Interfaces and the Interactions in Colloidal Dispersions

Preparation of monodispersed colloidal particles

A mean-field, lattice-based model of polymer melt intercalation in organically-modified mica-type silicates (OLS) has been developed. In general, an interplay of entropic and energetic factors determines the outcome of polymer intercalation. Free energy curves and their dependence on energetic and entropic factors suggest three possible equilibrium statesimmiscible, intercalated, and exfoliatedall of which have been experimentally observed. The entropic penalty of polymer confinement may be compensated for by the increased conformational freedom of the surfactant chain as the layers separate. When the total entropy change is small, small changes in the system's internal energy will determine if intercalation is thermodynamically possible. Complete layer separation, though, depends on the establishment of very favorable polymer−OLS interactions to overcome the penalty of polymer confinement. For alkylammonium-modified layered silicates, a favorable energy change is accentuated by maximizing the magnitude a...

Lattice Model of Polymer Melt Intercalation in Organically-Modified Layered Silicates

Blood compatibility of polyethylene oxide surfaces

Interfacial tensions and solubilizing ability of a microemulsion phase that coexists with oil and brine

Theory of the stabilization of dispersions by adsorbed macromolecules. II. Interaction between two flat particles

Theory of the stabilization of dispersions by adsorbed macromolecules. I. Statistics of the change of some configurational properties of adsorbed macromolecules on the approach of an impenetrable interface

F. Th. Hesselink

Papers

Theory of the stabilization of dispersions by adsorbed macromolecules. II. Interaction between two flat particles

Theory of the stabilization of dispersions by adsorbed macromolecules. I. Statistics of the change of some configurational properties of adsorbed macromolecules on the approach of an impenetrable interface

Density distribution of segments of a terminally adsorbed macromolecule