The Gordon‐Taylor equation. Additivity and interaction in compatible polymer blends

An analysis of the Gordon‐Taylor equation shows that its background is based on additivity. The corresponding parameter K = ρ1 Δα2 / (ρ2 Δα1), however, may include also an interaction contribution if the quadratic concentration term is neglected in a virial‐like extension of the glass transition temperature vs. composition expression. Then K becomes a real fitting parameter. It is shown that a distinction of the two cases is possible by using the corresponding linearized form of the respective equations. The discussion of data of polystyrene/poly(2,6‐dimethyl‐1,4‐phenylene oxide), styrene copolymers/poly(2,6‐dimethyl‐1,4‐phenylene oxide) and poly(methyl vinyl ether)/polystyrene blends gives evidence for the decisive influence of the stiffer component on the glass transition behaviour of compatible polymer blends.