Conformation of chains in cores of block copolymer micelles with solubilized homopolymer: a Monte Carlo study

Full Paper: A system of compatible self-avoiding polymer chains solubilized in spherical core of block copolymer micelles was studied by lattice Monte Carlo simulations. The core is modeled as a spherical cavity on a simple c ubic lattice, filled in partially by tethered (core-forming) chains and par tially by free (solubilized) chains. Molecular parameters (e.g., the ratio of the contour length of the model chains to the core radius) correspond to those in real micellar systems. The density (the fraction of lattice sites occupied) is 0.6 which corresponds to swollen micellar cores in real micel lar systems. Simulations yield a constant segment density profile in the co re. Both the tethered and solubilized chains acquire an ellipsoidal shape. The ellipsoids equivalent to both types of chains are more spherical than t hose in a melt and strongly oriented. The chains in the core show a Gaussia n-like behavior. Minor deviations from Gaussian behavior for tethered chain s are due to surface effects. [GRAPHICS] The segment density, rho (s), for systems with different lengths of solubil ized chains as a function of the radial distance, r. All systems studied co ntain 25 tethered chains of length L = 50 and varying numbers of solubilize d chains of different lengths: (i) 1250 solubilized chains (length L = 1) ( square), (ii) 50 solubilized chains (L = 25) (o), and (iii) 13 solubilized chains (L = 96) (Delta). Curves for tethered chains are represented by soli d lines, for solubilized chains by dashed lines.