In this paper we use the polymer adsorption theory of Scheutjens and Fleer to describe polymer brushes at spherical and cylindrical surfaces that are immersed in a low molecular weight solvent. We analyze the volume fraction profiles of such brushes, focusing our attention on spherical brushes in athermal solvents. These are shown to generally consist of two parts: a power law-like part and a part that is consistent with a parabolic potential energy profile of the polymer segments. Depending on the curvature of the surface, one of these two parts is more important, or may even dominate completely. We especially consider the distribution of the free end segments and the possible existence of a "dead zone" for these segments. Such a dead zone is actually found and is seen to follow a scaling law in the case of large curvatures. Furthermore, the effect of diminishing the solvent quality is considered for both the total volume fraction profile and the distribution of the end segments.

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Self-consistent-field (SCF) calculations are presented of a planar grafted polymer layer that interacts either with free polymer chains or with another grafted layer. Three different systems are studied. The first is a grafted polymer layer immersed in a polymer solution. The interaction between grafted and free polymer can significantly influence the grafted polymer volume fraction profile. For grafted chains that are strongly stretched the lattice calculations are compared with the theory of Zhulina, Borisov, and Brombacher (Macromolecules 1991, 24, 4679). Good agreement is found when the free chain length is far smaller than the grafted chain length. The scaling behavior of the penetration of free polymer into the grafted layer is also studied for this system. In the second type of system the interaction between two grafted layers in the absence of free polymer is considered. The lattice calculations agree well with the theory of Zhulina et al. In the third system free polymer is present between the interacting grafted layers. If this free polymer has a small chain length, its main effect on the interaction free energy is the compression of the free grafted layers, and only repulsion is found. However, for larger chain lengths a depletion attraction between the grafted layers appears.

We present Gibbs ensemble Monte Carlo simulations of monomer-solvent and polymer-solvent mixtures with soft interaction potentials, that are used in dissipative particle dynamics simulations. From the simulated phase behavior of the monomer-solvent mixtures one can derive an effective Flory-Huggins -parameter as a function of the particle interaction potential. We show that this -parameter agrees very well with the free energy difference between a monomer surrounded by solvent particles, and a solvent particle surrounded by solvent particles. We develop a new ''identity change'' Monte Carlo move to equilibrate the polymer-solvent mixtures. In this move a polymer chain from one box is exchanged with an equal number of solvent particles from the other box. At realistic densities this new move offers a large computational advantage over the convential insertion method for a polymer chain using a configurational bias Monte Carlo algorithm. The new algorithm is demonstrated for polymer-solvent mixtures with a chain length of up to 150 segments. Significant differences are found between the simulated polymer-solvent phase behavior and results predicted by mean-field theory. Finally, we fit a master-equation to the simulated binodal curves at different chain lengths. This function is used to make a quantitative comparison between the simulations and experimental data for the phase equilibrium of the polystyrene-methylcyclohexane system.

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We have incorporated chain stiffness and correlations between neighl:ioring bonds into a self-consistent field (SCF) lattice model for end-attached polymer layers (commonly known as "brushes"). An increase in the chain stiffness leads to an increasing brush height. This increase is directly related to the change of the length of a Kuhn segment in the polymer chain. Introducing correlations between neighboring bonds gives a higher density of the brush, corresponding to a decrease of the brush height. For not too stiff chains these two effects virtually compensate each other. Hence, the volume fraction profile of "real" grafted chains is nearly identical to that of a polymer brush consisting of freely jointed chains.

The dissipative particle dynamics (DPD) method is used to simulate shear flow between two flat plates. To test this technique, simulations were conducted of both constant and oscillatory shear of a simple fluid. The results of these simulations agree well with theoretical predictions. We subsequently applied our model to study the effect of shear flow on end-tethered polymer layers ("brushes"). When exposed to a constant shear flow, chains in a polymer brush are stretched in the direction of the flow, and the overall layer thickness decreases. This result is similar to what was found in previous simulation studies. However, in the present simulations solvent particles are taken into account explicitly. At low frequencies, the response of a brush to oscillatory shear is qualitatively similar to its response to constant shear. As the flow velocity changes during an oscillation cycle, the polymer chains are able to relax their configurations with respect to the shear rate. At higher frequencies the interpretation of the brush behavior becomes more difficult due to conflicting time scales of the polymer and solvent dynamics in the present DPD model.

We have studied the small-deformation rheology of a (semi-) two-dimensional model network of spherical particles, representing an adsorbed monolayer of protein at a fluid-fluid interface. The particles are confined at the interface in a steep potential well. A percolating network is generated through the formation of flexible but irreversible bonds between the particles. The shear rheology behavior of this system is similar to that of its three-dimensional counterpart, although the stress time correlation function does decay more slowly for the interfacial system. At not too high particle concentrations the dilatational rheology is completely dominated by the interactions due to the bonds between the particles. When the interface is compressed or expanded in one direction, the stress response is strongly orientation dependent. At high particle concentrations a compression of the interfacial film is very similar to a compression of a hard sphere system at the same concentration.