20 October 2009 Isothermal physical aging of thin PMMA films near the glass transition temperature
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Proceedings Volume 7493, Second International Conference on Smart Materials and Nanotechnology in Engineering; 749365 (2009) https://doi.org/10.1117/12.840160
Event: Second International Conference on Smart Materials and Nanotechnology in Engineering, 2009, Weihai, China
Abstract
The isothermal physical aging and the glass transition temperature (Tg) in PMMA thin films were investigated by means of differential scanning calorimetry (DSC). Freestanding thin film was obtained by spin coating onto a silicon wafer substrate and then releasing the coated film using a water floating technique for different molecular weights (MW = 120,000, 350,000, 996,000 g/mole) and film thicknesses (40~667 nm). The thin films were stacked in a DSC pan and isothermally aged for different aging times (ta = 1 and 12 h) and aging temperatures (Ta =105, 110 and 115 oC) below but near Tg. Enthalpy relaxation (▵HRelax) due to the isothermal physical aging vs. ▵Ta (Tg - Ta, driving force of aging) data showed that the enthalpy value increased with increasing ▵Ta, reached maximum, and then decreased as ▵Ta increases further. As film thickness decreases, ▵HRelax was rapidly reduced for samples below ~100 nm of film thickness near Tg (e.g., Ta =110 and 115 °C), indicating the suppression of physical aging. About 7~10 oC depression in Tg was observed for thinner films (~40 nm), compared to thicker films (~660 nm) in this study.
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J.-E. Nam, J.-E. Nam, J.-K. Lee, J.-K. Lee, C.-S. Oh, C.-S. Oh, } "Isothermal physical aging of thin PMMA films near the glass transition temperature", Proc. SPIE 7493, Second International Conference on Smart Materials and Nanotechnology in Engineering, 749365 (20 October 2009); doi: 10.1117/12.840160; https://doi.org/10.1117/12.840160
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