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Thickness-dependent structural relaxation in ultrathin glassy polymer films probed by wrinkling dynamics



Jun Y. Chung, Jack F. Douglas, Doyoung Moon, Christopher Stafford


The measurement of the Young's modulus and stress relaxation in ultrathin films is a notoriously difficult problem. Recent work has shown that the high frequency Young's modulus of ultrathin glassy polymer films can be measured by wrinkling-based method. Here, we show that the rate of structural relaxation and the temperature dependence of the modulus of these films can also be obtained by following the ‘relaxation' of strain-induced wrinkling patterns back to their flat equilibrium state. Measurements were performed below the glass transition temperature for a wide range of film thicknesses and temperatures to demonstrate the method. We find that the temperature dependence of the modulus conforms to a pattern of behavior found in diverse amorphous solids. Curiously, the apparent activation energy for the rate of wrinkling relaxation progressively decreases as the films becomes thinner, approaching a value comparable to that in the ‘complete absence of collective atomic motion', a situation found in bulk fluids at temperatures well above Tg. This trend, along with a broadening of the glass transition, is consistent with simulations and independent previous measurements, suggesting that film confinement progressively suppresses collective motion in ultrathin glassy polymer films.
The Journal of Chemical Physics


wrinkling, polymer, glass, dynamics, thin films, confinement, relaxation


Chung, J. , Douglas, J. , Moon, D. and Stafford, C. (2017), Thickness-dependent structural relaxation in ultrathin glassy polymer films probed by wrinkling dynamics, The Journal of Chemical Physics, [online],, (Accessed April 15, 2024)
Created October 15, 2017, Updated October 12, 2021