Simulation of the adsorption of symmetric diblock copolymers at the interface of the two monomeric homopolymers


A lattice model is presented to study a block copolymer compatibilizing two immiscible monomeric homopolymer blends. Each monomeric homopolymer occupies a single site on the lattice. The symmetric diblock copolymer AB is modeled by a self-avoiding walk on a cubic lattice. The two monomeric homopolymer fields interacting with the diblock copolymer are modeled by introducing two different kinds of vacancies in the lattice. These vacancies have the reduced pairwise interaction with A or B segments representing the homopolymer fields, namely εAS1 = 0, εBS2 = 0, εAS2 = εBS1 = εAB = ε ≥ 0. The two kinds of vacancies each occupy half of the lattice sites divided along the z direction, and forming a sharp interface at z = Lz/2. The equilibrium of copolymers dispersed in either phases vs localization at the interface is studied for a range of copolymer concentrations and different interaction energies. The number of chains per surface area, σ, was found to depend on the product of φb exp(εNc), where φb is the equilibrium concentration of the symmetric diblock copolymers in two phases, and Nc is the degree of polymerization of the copolymers. The dependence of σ on φb exp(εN c) is close to the Langmuir type adsorption. These results hold both at the cases that the copolymer chains in the bulk do not form micelles, and do form micelles. Micellization processes do not modify the overall function very much. That is partly due to the fact there is a large entropy loss when forming the micelles compared to the localization of the AB copolymer chains at the flat interface between the two monomeric homopolymer fields. © 1993 American Institute of Physics.

Publication Title

The Journal of Chemical Physics