Is chemical mismatch important in polymer solutions?

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Abstract
We study linear polymer solutions containing different chemical species within the framework of the direct renormalization method introduced by des Cloizeaux. We study the osmotic pressure and polymer radii of dilute solutions containing two chemically different polymers A and B both in good and θ solvent when the interaction between A and B monomers is repulsive. The central result is that in a good solvent in the asymptotic limit of infinite mass, polymers cannot tell each other apart: a polymer A cannot distinguish between a polymer A and a polymer B. The importance of the chemical difference between A and B monomers shows up only in corrections to scaling which are extensively studied. The study is made first for solutions of A and B chains having the same end-to-end distance and then generalized to the polydisperse case where A and B chains have different end-to-end distances. This allows to predict the behavior of the mutual A–B virial coefficient for two chains in a good solvent, in a θ solvent or in a selective solvent (good for A, θ for B). We then study semidilute solutions and show how the experimentally observed segregation between A and B chains is governed by corrections to scaling in a good solvent. An explicit expression is proposed for the osmotic pressure in that case. This study is also extended to very dilute solutions containing block copolymers.