Small Angle X-ray Scattering by Simultaneous Interpenetrating Polymer Networks: Composition and Temperature Dependence

Citations Over TimeTop 13% of 1997 papers

Abstract

The structure of simultaneously cross-linked interpenetrating polymer networks of poly(carbonate−urethane) (PCU) and poly(methyl methacrylate) (PMMA) has been studied by small-angle X-ray scattering (SAXS) with dependence on composition and temperature in a range from 298 to 373 K. At room temperature (298 K) the scattering intensity increases with decreasing scattering vector q and a q-4 dependence is found at large q values. The scattering profiles are compared with the Debye−Bueche theory for a statistical two-phase structure and a new recently developed hydrodynamic structure factor which describes the frustration of spinodal decomposition during the formation of simultaneous IPNs. Both approaches give the characteristic length of the frozen composition fluctuations between 2 and 35 nm for different compositions. With increasing temperature the scattering intensity of the sample with a characteristic length of 2 nm (60 wt % PCU) increases slightly at small q values. Above 353 K the scattering intensity increases tremendously and a maximum at q* becomes evident. The corresponding length l = 1/q* increases by a factor of about 2 with increasing temperature. The maximum in scattering intensity cannot be described by the Debye−Bueche theory, whereas it is in agreement with the hydrodynamic structure factor. Several reasons for the irreversible changes above 353 K will be discussed and supported by field gradient NMR measurements on the same sample.

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