A SMALL-ANGLE-SCATTERING STUDY OF THE PORE-ORIENTATION PERIODICITY INPOROUS POLYMER AND CARBON MATERIALS

Absolute-intensity, small-angle X-ray scattering is used to investigat e the pore structure of a carbon foam and its corresponding poly(acryl onitrile) foam precursor, both having a concentric band structure of u nusually large spacing. The poly(acrylonitrile) foam was prepared from a solidified blend, containing crystallized maleic anhydride, by subl iming the crystalline material. The scattering patterns for both foams reveal anisotropy in their pores and identical periodicity in the por e orientation as a function of distance along the radial direction. Th e period of pore-orientation oscillations, 3.5 mm, is the same as the period of macroscopically-visible bands present on the surface of both the carbon and poly(acrylonitrile) foams. Furthermore, the pore orien tations in both samples show the same oscillatory orientation as the m aleic anhydride crystals of the blend from which they were derived. Th e data suggest that a spherulitic orientation of the maleic anhydride crystals in the blend was imprinted on the polymer phase during crysta llization.