Crystallization-Arrested Viscoelastic Phase Separation in Semiconducting Polymer Gels

Jing He, Xiaoqing Kong, Yuhao Wang, Michael Delaney, Dilhan M. Kalyon, Stephanie S. Lee

Research output: Contribution to journalArticlepeer-review


Through a combination of rheological characterization and temperature-variable imaging methods, a novel gelation pathway in dilute solutions of a semiconducting polymer to achieve interconnected, crystalline networks with hierarchical porosity is reported. Upon rapid cooling, solutions of regioregular poly(3-hexylthiophene) in ortho-dichlorobenzene formed thermoreversible gels. Confocal microscopy revealed cooling-induced structural rearrangement to progress through viscoelastic phase separation (VPS), which arrested prematurely during the formation of micron-sized solvent-rich "holes"due to interchain crystallization. Cryogen-based scanning electron microscopy uncovered an interfibrillar network exhibiting nanosized pores. These networks formed to equal gel strengths when a third component, either small molecule phenyl-C61-butyric acid methyl ester or noncrystallizing regiorandom, poly(3-hexylthiophene), was added to the solution. Organic solar cells deposited with active layers from phase-separated solutions displayed 45% higher efficiency compared to reference cells. The demonstrated ability to arrest VPS enables control over the morphology of porous materials for applications ranging from membrane filtration to plastic foam manufacturing.

Original languageEnglish (US)
Pages (from-to)500-508
Number of pages9
JournalACS Applied Polymer Materials
Issue number3
StatePublished - Mar 8 2019


  • confocal microscopy
  • cryo-SEM
  • gelation
  • organic photovoltaics
  • polymer crystallization
  • rheology
  • viscoelastic phase separation

ASJC Scopus subject areas

  • Polymers and Plastics
  • Process Chemistry and Technology
  • Organic Chemistry


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