Structure and molecular dynamics of multilayered polycarbonate/polystyrene films.
Résumé
Multilayered film polycarbonate/polystyrene (PC/PS) comprising 257 layers with total thickness 125 µm was made by coextrusion process. The nominal thickness of PC layers was 680 nm, and the nominal thickness of PS layers was 290 nm. Additionally the control samples of PC and PS with the thickness of 125 µm were coextruded in the same way. There was reasonably good correlation between the PC and PS layers real thickness as measured by AFM and the estimated thickness determined from the processing parameters. Significant shift of glass transition temperature is observed in multilayer film: for PS component towards higher temperature while PC still being glassy and for PC towards lower temperature while PS being in rubbery phase. In order to investigate the amplitude and geometry of fast segmental motions, the LG-CP NMR technique under fast magic-angle spinning was used. 2D 13C - 1H LG-CP spectra of PC, PS and PC/PS 70/30 were recorded at various temperatures. Cross sections of aromatic carbons spectra show us the influence of PC on PS and vice versa. It gives us also the information about PS and PC segmental motion as a function of temperature: above the glass transition temperature of PS, the PC component of a multilayer film, although still being in glassy state, becomes more flexible.
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