Gels and semicrystalline clathrate samples formed by syndiotactic polystyrene (sPS) with 1,2-dichloroethane (DCE) and 1-chloropropane (CP) have been investigated, for the entire composition range from pure solvent to pure polymer, by wide-angle X-ray diffraction (WAXD) and Fourier transform infrared spectroscopy (FTIR). WAXD measurements show that, at least for gels with polymer concentration higher than 0.1 g/g, peaks typical of sPS/DCE and sPS/CP clathrate structures are present. FTIR measurements show the occurrence of the same kind of formational selectivity for DCE (in favor of the trans conformer) and the absence of conformational selectivity for CP for both gel and clathrate samples. Moreover, the molar ratio between styrenic units and DCE in the crystalline phase of the gels, as evaluated from FTIR data, is nearly constant (3.6 ( 0.3) for the entire composition range; that is close to the 4/1 styrenic unit/guest molecule ratio, which has been observed for the clathrate crystal structure. The whole set of results indicates that the polymer-rich phase forming the cross-link domains of these sPS gels is a crystalline clathrate phase. Both WAXD and FTIR measurements indicate that this clathrate crystalline phase, when present in the gels, would be characterized by coherent lengths being much higher along the chain axes than perpendicular to them.
Clathrate phase in syndiotactic polystyrene gels
DANIEL, Christophe;GUERRA, Gaetano;
2002-01-01
Abstract
Gels and semicrystalline clathrate samples formed by syndiotactic polystyrene (sPS) with 1,2-dichloroethane (DCE) and 1-chloropropane (CP) have been investigated, for the entire composition range from pure solvent to pure polymer, by wide-angle X-ray diffraction (WAXD) and Fourier transform infrared spectroscopy (FTIR). WAXD measurements show that, at least for gels with polymer concentration higher than 0.1 g/g, peaks typical of sPS/DCE and sPS/CP clathrate structures are present. FTIR measurements show the occurrence of the same kind of formational selectivity for DCE (in favor of the trans conformer) and the absence of conformational selectivity for CP for both gel and clathrate samples. Moreover, the molar ratio between styrenic units and DCE in the crystalline phase of the gels, as evaluated from FTIR data, is nearly constant (3.6 ( 0.3) for the entire composition range; that is close to the 4/1 styrenic unit/guest molecule ratio, which has been observed for the clathrate crystal structure. The whole set of results indicates that the polymer-rich phase forming the cross-link domains of these sPS gels is a crystalline clathrate phase. Both WAXD and FTIR measurements indicate that this clathrate crystalline phase, when present in the gels, would be characterized by coherent lengths being much higher along the chain axes than perpendicular to them.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
