Surface energy gradient driven convection for generating nanoscale and microscale patterned polymer films using photosensitizers

Chae Bin Kim, Dustin W. Janes, Dana L. McGuffin, Christopher J. Ellison

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

The Marangoni effect describes how fluid flows in response to gradients in surface energy. This phenomenon could be broadly harnessed to pattern the surface topography of polymer films if generalizable techniques for programming surface energy gradients existed. Here, a near UV-visible light (NUV-vis) photosensitizer, 9,10-dibromo-anthracene (DBA), was doped into thin films of a model polymer, poly(isobutyl methacrylate). After exposure to light through a photomask and heating above the glass transition, thermolysis of photo-oxidized DBA and grafting to the polymer promoted flow of the film material into the exposed regions. This mechanism did not significantly alter the molecular weight of PiBMA or the film's glass transition temperature, but resulted in an increase in film surface energy as indicated by a decrease in water contact angle. Film height variations of 580 nm were produced using a mask with 12.5 μm features; a mask with 800 nm features was also employed to generate topographic features of corresponding width without expensive contacting equipment. Due to the broad absorbance spectra of DBA, highly accessible and/or unconventional light sources may be employed in this process; this advantage was demonstrated by patterning with sunlight. The nonspecific radical-mediated nature of the DBA grafting reaction makes this a promising approach for many classes of polymers.

Original languageEnglish (US)
Pages (from-to)1195-1202
Number of pages8
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume52
Issue number18
DOIs
StatePublished - Sep 15 2014

Keywords

  • convection
  • diffusion
  • photochemistry

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