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We calculate the scattering intensity of dilute and semi-dilute solutions of star polymers. The star conformation is described by a model introduced

We study the aggregation of diblock copolymers in a selective solvent as a function of the asymmetry of the copolymer chains. When the shorter block is in a poor solvent, our mean-field approach predicts copolymer micellization in spherical or cylindrical geometries. For large collapsed blocks a dense lamellar phase is formed in an excess of solvent. A further increase of the size of the molten blocks leads to the formation of reverse micellar structures, where small spherical swollen cores are surrounded by a majority matrix of molten chains.

We examine the effect of long-range surface interactions on surface wetting phase transitions in polymer mixtures. Within a perturbation scheme, we have found an analytic solution for the volume-fraction profile near the surface which can be compared with that obtained from a model with short-range surface interactions only. We find that the long-range interactions should not be ignored in the interpretation of recent experimental results. PACS numbers: 68.45.Gd, The concentration of a binary polymer mixture displays an inhomogeneous profile near a wall surface due to the preferential adsorption of one component to the wall surface. Theoretical models, accounting for short-range interactions between monomers of the polymer mixture 1 and the wall surface, 2,3 predict wetting transitions from a wet state, characterized by a macroscopic layer of the phase preferred by the wall, to a nonwet state, characterized by a microscopic layer of the same phase. 4 The recent forward-recoil spectrometry, secondary-ion mass spectroscopy, and neutron-reflectivity results by Jones et al., indicate that the surface adjacent to blends of deuterated and normal polystyrene is indeed enriched. 5,6 However, the neutron reflectivity measured by these authors shows significant deviations from the reflectivity deduced from the mean-field volume-fraction profile of Schmidt and Binder. 3 These deviations are unlikely to be due to nonclassical effects since it is known that the thermodynamic properties of polymer mixtures can be well described by a mean-field theory. 1 As argued by Fisher, any long-range interaction is always relevant in the three-dimensional wetting problem. 7 However, the effects of long-range interactions of the van der Waals or dipole-dipole type near the surface of polymer mixtures were ignored in previous theories. 2,3 In this Letter, we examine the mean-field effects of these long-range interactions on wetting phase transitions in polymer mixtures.Our model is based on the inclusion of LennardJones-type interactions. The analysis starts from the free-energy model 2,3,8,9 /fy(z)] _ f OO ) term is the Flory-Huggins free energy of mixing, 1 G(0) --7-0ln0+-7-(l -0)ln(l -^)+^(l -0) ,where x is the Flory segmental interaction parameter, x and NA and Ng are the degrees of polymerization of polymers A and B, respectively. In this Letter, we take N A =NB for simplicity. The coefficient K{(J>) of the gradient term has the form K-(0)=6 2 /360(1--0),where b is the effective Kuhn length. 1,8,9 The last two terms in Eq. (1) represent the contributions from the wall-surface-polymer interactions. The perturbation effect due to the direct contact interaction of the polymer and the wall surface is described by / (j) (0o), which is a function of the v...

We study theoretically mixed solutions of homopolymer and diblock copolymer chains. The solvent is a poor solvent for the homopolymers and a selective solvent for the copolymers. We find that the formation of copolymer micelles containing also the insoluble chains allows for an increased solubility of the homopolymers in the solution. In agreement with experiments, we find also that the solubilization power of the micelles, that is, the maximum amount of total homopolymer weight solubilized per unit weight of copolymers in solution, decreases strongly with the homopolymer index of polymerization.