Bashir, Z.; Church, S. P.; Price, D. M.; The formation of polymer-solvent complexes of polyacrylonitrile from organic solvents containing carbonyl groups. Acta Polymerica 44(5) (1993) 211-218
The crystallisation behaviour on cooling of concentrated solutions of polyacrylonitrile in two organic solvents, g-butyrolactone and ethylene carbonate, was investigated. g-butyrolactone is a liquid but ethylene carbonate is a crystalline solid at 20°. Wide-angle x-ray diffraction studies showed that the peaks from the solvent-containing gel films were different from those in the dry polyacrylonitrile powder. Polarised-IR spectroscopy measurements conducted on uniaxially drawn gel films indicated not only preferential orientation of the nitriles perpendicular to the draw direction but also orientation of the residual solvent in such a way as to suggest pairing of the g-butyrolactone or ethylene carbonateI molecules with the nitriles on the chains. It is suggested that the X-ray diffractograms of the gels may be due to the formation of polymer-solvent complexes during crystallisation of polyacrylonitrile from solvents with carbonyl groups. DSC showed gel-melting endotherms on heating and crystallisation exotherms on cooling.
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