Tracing the spontaneous mixing and mobility of miscible polymer blends using differential scanning calorimetry [Cellulose acetate‐poly(styrenephosphonate ester)

Abstract

AbstractA method in which the dissolution of a miscible polymer pair is traced in a differential scanning calorimetry cell is described. The polymer blend is initially prepared as an heterogeneous system with microdomains of one component embedded in the continuous matrix of the second polymer. Annealing the system in the DSC cell above the glass‐transition temperature causes a spontaneous mixing of the polymer pair which can be observed by the progressive shift of the Tgs of both components until they merge. The time scale for dissolution and aspects of mass‐transport phenomenon are thus determined for the specific blend, cellulose acetate‐poly(styronephosphonate ester). Rather sharp progressive shifts of the Tgs are shown to prevail without significant broadening of the transition curve (ΔTg). Mass‐transport analyses supported by electron microscopy observation of the blend, before and after annealing, suggest that the domain sizes remain nearly unchanged and the physicochemical makeup of the phase boundary interfaces determines the time scale of dissolution in the system. A model from which mean‐value diffusion coefficients are calculated for both components at different annealing temperatures is reported.