Towards a better mixing of two incompatible polymers by casting from solution without compatibilizer

The influence of the molecular mass of two incompatible polymers on their miscibility in the solid state without compatibilizer after casting from solution

“…The same experiment has been performed with the film of PS (M W ϭ 4000)/PMMA (M W ϭ 60,000) mixture and the SEM micrograph is presented in Figure 1(b). For the PS/PMMA mixture, benzene presents the lower selectivity (⌬a ϭ 0.03), as we have already mentioned, and according to our previous work, 1 we observe a good dispersion of the two phases (domains of the order of 7 m) [ Fig. 1(a)].…”

“…In a recent paper, 1 we have shown that two incompatible polymers can present a relatively good degree of miscibility in the solid state if the blends are obtained by casting from a nonselective solvent for these polymers (i.e., a solvent in which the two polymers present comparable solubilities. More precisely, we have studied the polymer blends polystyrene/poly(methyl methacrylate) and polystyrene/ poly(oxyethylene).…”

“…On the con-trary, for the second pair of polymers an increase of the temperature induces an increase of the selectivity of the solvent and the two polymers present less mixing in the solid state when the casting is performed at elevated temperature. The Scanning Electron Microscopy has shown that when the films of the two incompatible polymers were obtained by casting from a nonselective solvent their domains can be reduced to 5 m. 1 The study of the solution properties of mixtures of two polymers has shown that repulsion between them increases when (i) the selectivity of the solvent increases, (ii) the difference between their molecular masses increases, and (iii) their molecular masses become very low. 4,5 Accepting that we have a memory effect when we go from the solution to the solid state, 1,6 we must expect that the miscibility of the two polymers in the solid state will become gradually lower when the difference between their molecular mass increases and that the better miscibility will be achieved when their molecular masses are comparable and relatively high.…”

Difficult reptation of star-shaped polystyrenes in their blends with poly(methyl methacrylate)

“…[6,7] We have found that the repulsion between PS and PMMA is higher on using star PS, which is opposite to the memory effect observed for two linear polymers when going from solution to the solid state. [4,5,8] Consequently, we must attribute the difficulty in phase separation between star PS and PMMA only to the difficult reptation of the star PS.…”

“…1 but evaporation of the solvent was now performed at 50 8C. As shown previously by us, [4,5] increasing the temperature provokes a decrease of the incompatibility between PS and PMMA, when the two polymers were dissolved in ethyl acetate. According to the memory effect, a better degree of mixing of these two polymers is obtained, after evaporation of the solvent, in the solid state.…”