Halo formation in asymmetric polyetherimide and polybenzimidazole blend hollow fiber membranes

Tai-Shung Chung, X. L. Zhen-Liang, Cheng Hon Alfred Huan

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


For the first time, we have reported a halo (ring) formation occurred in the cross-section of integrally skinned asymmetric membranes. These membranes were wet-spun from solutions containing 30 and 33 wt % of 95/5 and 90/10 polyetherimide (PEI)/polybenzimidazole (PBI). Both Imaging X-ray Photoelectron Spectroscopy (XPS) and Dynamic Mechanical Analyzer's (DMA) data suggest PEI and PBI form miscible blends the 'halo' is not chemically different from the matrix and is most likely a physical phenomenon of unique pore morphology. In other words, uniform porosity was created in the middle of hollow fiber cross-section area, which performs as a filter for light transmission. We found that the addition of PBI in PEI/DMAc solution not only depresses the macrovoid formation, but also changes the precipitation path: nucleation growth vs. spinodal decomposition. The formation of a halo within a membrane is possibly due to the fact that a uniform nucleation growth occurs in the ring region during the early stage of phase separation because of high solution viscosity and diffusion controlled solvent-exchange process, and then separation grows in the mechanism of spinodal decomposition from small amplitude composition fluctuations.

Original languageEnglish (US)
Pages (from-to)1575-1585
Number of pages11
JournalJournal of Polymer Science, Part B: Polymer Physics
Issue number14
StatePublished - Jul 15 1999

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry


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