Order, short-range blends

Blends of polystyrene (PS) and PC are immiscible at all temperatures. Figures 2 and 3 show the WANS from PS/PC blends of several compositions. The weak peak at q, = 0.6 A disappeared, but the peak at q, = 1.26 A persisted and increased in intensity with increasing PC blend content, indicating that the short-range order of the PC was unaffected by the addition of the immiscible PS. 

Amorphous PC exhibits short-range order, which is evident from a WANS peak at q, = 1.27 A. In two-phase blends of PC with eithw polystyrene or sulfonated polystyrene ionomers, the short-range order is retained by the PC. However, in the one-phase region, the PC order is diminished, as evident from a reduction in the WANS peak intensity and increase in the peak broadness. The reduction of the PC short-range order in the miscible blends is believed to result from the intimate mixing of the two polymers, which disrupts the parallel packing of PC chain segments with trans-trans conformations. 

Destruction of Short-Range Order in Polycarbonate-Ionomer Blends Ryan Tucker et al. 

DSC curves for L and L-PU blends (unexposed and exposed) are displayed in Fig. 10. The authors attributed the transition near -52°C to the Tg of the soft PU segments and that at about +9°C was attributed to the microcrystalline melting of the soft segments. Similarly, the transition observed at 90°C was probably due to the breakup of short-range ordered hard segments. The transitions for blended specimens occur in the same temperature interval as for the neat PU. The glass transition temperature, barely detectable for L at 125°C, indicates that the L-PU blend exists in two distinct phases which, in turn, confirms their observation by microscopy. From the DSC results, the authors concluded that DSC confirms the immiscibility of L with PU at blend ratios used in the study. 

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