Critical temperature shifts in thin polymer blend films

摘要

We present the first comprehensive theory for the phase behavior of thin polymer blend films. Based on the Landaundash;Ginzburg free energy functional, our mean field analysis incorporates the influence of finite size effects and surface interactions, and explicitly considers surface segregation. The procedure for calculating the full phase diagram is provided. In symmetric blends with neutral surfaces, the reduced critical temperature shiftstare obtained in exact analytical forms. Our predictions are in good agreement with our simulations. For polymers withNgsim;100 (Nbeing the polymerization index) in films much thinner than fully extended chain dimensionsNl, a unique scaling behaviortprop;Lminus;1(i.e., the inverse film critical temperature depends linearly on 1/L) is found. WhenLGt;Nl, an Isinghyphen;type behaviortprop;N0.59Lminus;1.59is expected.