We utilize neutron reflectometry (NR) to probe the amount of residual solvent inside thin polystyrene (PS) and poly(methyl methacrylate) (PMMA) films spin-coated from deuterated toluene polymer solutions onto silicon substrates . The effect of thermal treatment at temperatures below and above the glass transition of PS and PMMA are examined to determine how these treatments affect the residual solvent. The parameters investigated include the total film thickness h and molecular mass M for PS and only h for PMMA. We find that relative amount of solvent in PMMA films is less than a few percent, while no detectable amount of residual solvent was found in the PS films. The residual solvent content of the PMMA films had no measureable dependence on h. These results are corroborated utilizing Fourier Transform infrared (FTIR) spectroscopy. We discuss our observations in comparison with a large body of seemingly conflicting observations on residual solvent in polymer thin films.
Pub Type: Journals
Residual solvent, Polymer, Thin film, Neutron reflectometry