FTIR ATR Analysis for Microstructure and Water Uptake in Poly(methyl methacrylate) Spin Cast and Langmuir-Blodgett Thin Films

Peter Sutandar, Dong June Ahn, Elias I. Franses

Research output: Contribution to journalArticle

88 Citations (Scopus)

Abstract

Spin cast and Langmuir-Blodgett (LB) films of atactic PMMA [poly(methyl methacrylate)] were studied at 25 °C by FTIR ATR (Fourier transform infrared spectroscopy, attenuated total reflection) spectroscopy before and after annealing at 140 °C and after contact with water vapor or liquid. The dichroic ratios of the carbonyl groups revealed that the average molecular orientations of the films remained unchanged upon annealing and also upon exposure to water. However, annealing helped avoiding cracks which appeared in the nonannealed film after contacting liquid water. The absorbances of individual water bands (of the non-hydrogen-bonded monomers, hydrogen-bonded dimers, larger clusters, and associated chains of water) were determined by detailed spectral analysis and compared with a one-dimensional Fickian model. The absorbance data for the annealed spin cast film of thickness of 5.4 μm showed poor fit to the one-dimensional Fickian diffusion model, but the apparent diffusion coefficient, Dapp, ranged from 5 × 10−10 to 4 × 10−11 cm2/s. The process of film hydration was found to precede the transfer of bulklike water. For the annealed LB and spin cast films of thickness of 0.1μm, Dapp ranged between 10−13 and 10−15 cm2/s. It was estimated from ATR carbonyl band intensities that the thin films were about 44% more dense than the thick film, indicating that they had a tighter structure with fewer structural defects or voids. Having more hydrophobic and less rough surface, the LB film showed a longer initial delay in liquid water transport than the spin cast film of the same thickness.

Original languageEnglish
Pages (from-to)7316-7328
Number of pages13
JournalMacromolecules
Volume27
Issue number25
DOIs
Publication statusPublished - 1994 Dec 1

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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