Changes in morphology and transport characteristics of polysulfone membranes prepared by different demixing conditions

Myeong Jin Han, Dibakar Bhattacharyya

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84 Scopus citations


A polymer solution film, which is cast from a homogeneous polysulfone (PS) solution (15 wt%) in dimethylformamide (DMF), demixes by liquid-liquid phase separation due to nucleation of polymer-poor phase with sorption of water vapor from atmosphere. The separated two liquid phases continue to grow until the polymer-rich phase solidifies. However, the polymer-rich phase in the liquid-liquid phase-separated solution can demix again before precipitation of the phase. The demixing of the polymer-rich phase on the top layer of the film is induced by kinetically fast demixing conditions, such as rapid mass transfer between nonsolvent (water) and solvent (DMF) in a nonsolvent bath. Morphology of solidified membranes shows that when a membrane structure is established by water vapor sorption alone, the liquid-liquid phase separated solution film forms closed cell-like structures in a whole cross section including surface region and has round pores on the top surface. Even though pore sizes on the surface of the membrane are more than 1 μm, those pores do not work as active pores for membrane performance. A skin structure of a membrane precipitated by fast or instantaneous demixing in a water bath includes nodules or polymer aggregates which can be distinguished from the cell-like structures formed by the liquid-liquid phase separation due to nucleation of the polymer-poor phase. The membrane including nodules in the skin region has higher surface area and broader pore size distribution than the membrane which consists of the cell-like structures. The crack-like pores on the surface of the former contribute to the permeation characteristics of the membrane.

Original languageEnglish
Pages (from-to)191-200
Number of pages10
JournalJournal of Membrane Science
Issue number3
StatePublished - Jan 31 1995


  • Demixing
  • Gas adsorption
  • Membrane formation
  • Morphology
  • Polysulfone

ASJC Scopus subject areas

  • Biochemistry
  • Materials Science (all)
  • Physical and Theoretical Chemistry
  • Filtration and Separation


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