Sorption kinetics of methanol in thin poly(methyl methacrylate) films studied by optical reflectivity

Koichiro Hori, Hisao Matsuno, Keiji Tanaka

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


To study the thickness dependence of methanol diffusion into poly(methyl methacrylate) (PMMA) films, an experimental method based on optical reflectivity was proposed. The method can cover a thickness range from the micrometre down to the nanometre scale using a single set-up. Methanol molecules diffuse into PMMA following a Case II mechanism in which they induce segmental motion of the matrix polymer. We observed two diffusion modes, fast and slow, assignable respectively to the outermost layer and the remaining internal region including the substrate interface. When the film becomes thinner, the ratio of the interfacial area to the total volume increases. This results in slowing down of the methanol diffusion due to the contribution of the depressed segmental mobility at the substrate interface. Interestingly, the thickness of the mobility-enhanced layer at the outermost region of the film similarly decreased with decreasing total thickness owing to the effect of the substrate interface.

Original languageEnglish
Pages (from-to)10319-10326
Number of pages8
JournalSoft Matter
Issue number21
Publication statusPublished - Nov 7 2011

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Condensed Matter Physics

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