CRYSTALLIZATION AND MORPHOLOGY OF POLY(ETHYLENE OXIDE)-P-NITROPHENOL MOLECULAR-COMPLEX CRYSTALLIZED FROM THE MELT

We report here a study on the crystallization of a new crystalline complex made from poly-(ethylene oxide) (PEO) and p-nitrophenol (pnp). The crystal structure of this complex was previously determined by X-ray diffraction and polarized FTIR. When the molecular weight of the polymeric component is either 6000 or 35 000, melt-grown crystals exist as non-integral-folded (NIF) lamellae and not as the integral-folded (IF) species generally observed for pure oligomeric PEO. Consequently, it may be presumed that the mode of growth of such a complex is similar to that of a high molecular weight polymer. We have measured the linear spherulitic growth rates of the complex in the crystallization temperature range of 25-70-degrees-C. The log G versus T(c) curves are surprisingly similar for both molecular weights, which present three branches with two intersection points at T(c) = 58 and 65-degrees-C (the same temperature for both M(w)). From X-ray diffraction patterns and polarized FTIR spectra of the PEO-pnp spherulites, we observed that, for crystallization temperatures below 58-degrees-C and above 65-degrees-C, the growth face is (100) but, in between these two temperatures, the leading facet corresponds to a (010) crystallographic face. This is an additional example where the breaks in the curve giving the thermal dependence of the growth rate are not signatures of regime transitions.