Microphase Separation within a Comb Copolymer with Attractive Side Chains: A Computer Simulation Study

Computer simulation modelling of a flexible comb copolymer with attractive interactions between the monomer units of the side chains is performed. The conditions for the coil-globule transition, induced by the increase of attractive interaction, ε, between side chain monomer units, are analysed for different values of the number of monomer units in the backbone, N, in the side chains, n, and between successive grafting points, m. It is shown that the coil-globule transition of such a copolymer corresponds to a first-order phase transition. The energy of attraction (ε) required for the realisation of the coil-globule transition decreases with increasing n and decreasing m. The coil-globule transition is accompanied by significant aggregation of side chain units. The resulting globule has a complex structure. In the case of a relatively short backbone (small value of N), the globule consists of a spherical core formed by side chains and an enveloping shell formed by the monomer units of the backbone. In the case of long copolymers (large value of N), the side chains form several spherical micelles while the backbone is wrapped on the surfaces of these micelles and between them.

Macromolecular theory of solvation and structure in mixtures of colloids and polymers

The structural and thermodynamic properties of mixtures of colloidal spheres and non-adsorbing polymer chains are studied within a novel general two-component macromolecular liquid state approach applicable for all size asymmetry ratios. The dilute limits, when one of the components is at infinite dilution but the other concentrated, are presented and compared to field theory and models which replace polymer coils with spheres. Whereas the derived analytical results compare well, qualitatively and quantitatively, with mean-field scaling laws where available, important differences from ``effective sphere'' approaches are found for large polymer sizes or semi-dilute concentrations.Comment: 23 pages, 10 figure

Scale-free static and dynamical correlations in melts of monodisperse and Flory-distributed homopolymers: A review of recent bond-fluctuation model studies

It has been assumed until very recently that all long-range correlations are screened in three-dimensional melts of linear homopolymers on distances beyond the correlation length $\xi$ characterizing the decay of the density fluctuations. Summarizing simulation results obtained by means of a variant of the bond-fluctuation model with finite monomer excluded volume interactions and topology violating local and global Monte Carlo moves, we show that due to an interplay of the chain connectivity and the incompressibility constraint, both static and dynamical correlations arise on distances $r \gg \xi$. These correlations are scale-free and, surprisingly, do not depend explicitly on the compressibility of the solution. Both monodisperse and (essentially) Flory-distributed equilibrium polymers are considered.Comment: 60 pages, 49 figure

Monte-Carlo simulation of multiple chain systems : screening length in two- and three-dimensional spaces

We describe the results of Monte-Carlo calculations of multichain systems with excluded volume interactions. We studied the concentration dependence of the screening length ξ for three-and two-dimensional systems. It is observed that ξ diminishes steadily with the increase in the concentration C of chain molecules. The decrease is more pronounced for the two-dimensional system. For C ≥ 0.05 ξ is found to scale with density as C-b, where b = 0.65 ± 0.04 for d = 3 and b = 1.17 ± 0.09 for d = 2. The obtained exponents are in reasonable agreement with the scaling prediction : b = 3/4 (d = 3) and b = 3/2 (d = 2).Dans ce travail on étudie par la méthode de Monte-Carlo les chaînes flexibles de polymères en solution semi-diluée. On calcule la dépendance de la longueur d'écran ξ en fonction de la fraction en volume C du polymère à 2 et 3 dimensions. On montre que, dans les deux cas, lorsque C augmente, la quantité ξ décroît comme ξ ∼ C-b où b dépend de la dimensionalité d. On trouve que, pour C ≥ 0,05 et d = 3, la valeur de b = 0,65 ± 0,04 et, pour d = 2, b = 1,17 ± 0,09. Ces résultats sont qualitativement en accord avec les prédictions des lois d'échelle : b = 3/4 (d = 3) et b = 3/2 (d = 2)