Two allotropic forms for the poly(ethylene oxide)-resorcinol molecular complex

Differential scanning calorimetry indicates that the poly(ethylene oxide)-resorcinol molecular complex crystallizes into two allotropic forms, denoted here as alpha and beta forms, respectively. The phase diagram of the PEO-resorcinol system, involving only the already known allotropic alpha form of the molecular complex, is obtained by differential scanning calorimetry. The alpha form of the molecular complex crystallizes as unbanded spherulites. The reflections of the wide-angle X-ray patterns from stretched film and spherulites of the alpha form are indexed on the basis of an orthorhombic unit cell (a = 1.050 nm, b = 1.013 nm, c = 0.9776 nm), with the Pna2 sub(1) space group. This unit cell differs widely from the monoclinic unit cell previously reported by Myasnikova et al. As shown from polarized FTIR spectroscopy, the 2-5 axis of the resorcinol molecule is parallel to the a reciprocal parameter of the unit cell of the molecular complex. The benzene ring of the resorcinol molecule is nearly perpendicular to the c crystallographic parameter. The new allotropic form of the poly(ethylene oxide)-resorcinol molecular complex ( beta form) crystallizes as banded spherulites. This beta form of the molecular complex is also studied by differential scanning calorimetry, optical microscopy, and Fourier transform infrared spectroscopy. The determination of the unit cell for the beta form of the PEO-resorcinol molecular complex is still in progress.