A lattice model describing hydrogen bonding in polymer mixtures

Abstract

A Flory lattice model is used to obtain an expression for the free energy of mixing polymers that hydrogen bond. The derivation is based on the determination of the probability that a mixture of the nonhydrogen bonded chains would spontaneously occur in a configuration equivalent to the hydrogen bonded system. Our result has three parts. The usual contribution to the free energy from mixing covalent chains, a contribution from the hydrogen bonds that is equal to the result that would be obtained if the segments were not covalently linked, and a ‘‘correction’’ term that accounts for the excess entropy of mixing introduced by the second term. A consequence of this model is that there should be no dependence of the equilibrium constants describing hydrogen bonding upon covalent chain length.