Monodisperse polystyrene (PS), with molecular weight of 1.8 x 106, was dissolved and refluxed in cyclohexane, keeping the polymer concentration below the critical value for chain shrinkage. After rapidly freezing the solution by injecting it directly into liquid nitrogen, the solvent was sublimed so that expanded chain coils with few entanglements could be obtained. The glass transition temperature, Tg, for this material was found to be 45°C lower than that of the ordinary PS, even after annealing up to 180°C. Comparison of the infra-red spectra showed some conformational differences between the rapidly frozen and the ordinary PS. Dilute polymer solution was rotated in a flask while it was immersed in a cold ethanol bath, so that the solution was frozen relatively slowly. After the solvent was sublimed, the resulting PS showed a lower Tg in its first d.s.c, scan, but exhibited the same Tg as ordinary PS after annealing.
Посилання на статтю:
Glass transition of expanded polystyrene coils / Gi Xue, Yun Lu, Gaoquan Shi and Qinpin Daif // Polymer. – 1994. – Vol 35. – P. 892-894.