Surface Induced Spinodal Decomposition Leading to Layered Coexisting Phases

Surface Induced Spinodal Decomposition Leading to Layered Coexisting Phases 

The variation of the chemical composition of the substrate (not realized in a continuous tunable fashion) leads to drastic modifications of surface fields exerted by the polymer/substrate (i.e.,II) interface [94,97, 111, 114,119]. The substrate may, for instance, change contact angles with the blend phase from zero to a finite value. As a result the final morphology changes from a layered structure of Fig. 5b into a column structure of Fig. 5c [94,114]. On the other hand our very recent experiment [16] has shown that the surface fields are temperature dependent. Therefore, although it has been shown that surface-induced spinodal decomposition yields coexisting bilayer structure (Fig. 5b) at a singular temperature [114,115], that in principle may not be necessary true for other temperatures. This motivated our comparative studies [107] on coexistence compositions determined with two techniques described above interfacial relaxation and spinodal decomposition. 

Surface induced spinodal decomposition leads, for properly controlled surface fields, to a two layer structure characteristic for coexisting phases. Hence it may be used to determine the coexisting conditions in a more convenient way that with the interfacial relaxation method as the initial bilayer geometry may be avoided. In practical terms the overall composition of the whole thin film may be much better controlled in experiments involving spinodal decomposition. Therefore in experiments studying the equilibrium composition vs depth pro- 

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