As in the case for dilute polymer solutions, the first two terms on the right-hand side represent the entropy of mixing. For large polymers of N A ≫ ≫ 1 and N B ≫ ≫ 1 these terms are negligibly small. This implies that for a stable mixture to exist χ χ < 0 , so for polymers A and B to blend their segments must attract one another.