A morphological study of membranes obtained from the systems polylactide-dioxane-methanol, polylactide-dioxane-water, and polylactide-N-methyl pyrrolidone-water

P. van de Witte, H. Esselbrugge, P.J. Dijkstra, J.W.A. van den Berg, J. Feijen

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Abstract

The influence of liquid-liquid demixing, solid-liquid demixing, and vitrification on the membrane morphologies obtained from several polylactide-solvent-nonsolvent systems has been investigated. The polymers investigated were the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA). The solvent-nonsolvent systems used were dioxane-water, N-methyl pyrrolidone-water and dioxane-methanol. For each of these systems it was attempted to relate the membrane morphology to the ternary phase diagram at 25°C. It was demonstrated that for the amorphous poly-DL-lactide the intersection of a glass transition and a liquid-liquid miscibility gap in the phase diagram was a prerequisite for the formation of stable membrane structures. For the semicrystalline PLLA a wide variety of morphologies could be obtained ranging from cellular to spherulitical structures. For membrane-forming combinations that show delayed demixing, trends expected on the basis of phase diagrams were in reasonable agreement with the observed membrane morphologies. Only for the rapidly precipitating system PLLA-N-methyl pyrrolidone-water were structures due to liquid-liquid demixing obtained when structures due to solid-liquid demixing were expected. Probably, rapid precipitation conditions promote solid-liquid demixing over liquid-liquid demixing, because the activation energy necessary for liquid-liquid demixing is lower than that for crystallization.
Original languageEnglish
Pages (from-to)2569-2578
Number of pages9
JournalJournal of polymer science. Part B: Polymer physics
Volume34
Issue number34
DOIs
Publication statusPublished - 1996

Keywords

  • METIS-105386
  • IR-71257
  • membrane formation
  • liquid-liquid demixing
  • Polylactide
  • Morphology
  • Crystallization

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