Lattice theory for multicomponent mixtures of copolymers with internal degrees of freedom in heterogeneous systems

We have generalized the lattice theory recently presented by Evers, Scheutjens, and Fleer (Macromolecules 1990, 23, 5221) by extending it to the case where the polymer segments possess internal degrees of freedom. The theory is able to describe the adsorption from a multicomponent mixture of arbitrary composition of polymers and solvents where the segments of a polymer may be of different types and possess internal degrees of freedom. The use of internal states results in effective segment-segment interaction parameters, which are temperature and density dependent. This simple polymer model has previously been useful for describing the existence of a lower consolute point occurring in some aqueous polymer solutions and for predicting the conformational equilibrium of poly(ethylene oxide) in homogeneous solutions. We also present results from an application of our extended theory on the adsorption of Pluronic (a triblock copolymer) from aqueous solution. The nontrivial and prominent increase of the Pluronic adsorption as the temperature of the solution reaches the cloud point from below is accurately reproduced by the theory.