Recently, we developed a method for quantifying the complete uniaxial stress-strain relationship for ultrathin polymer films. The key to this method is the use of liquids to help support ultra-thin, often fragile, films. Although this method has provided new insights into mechanical properties and deformation mechanisms for dimensionally-confined polymer systems, for some polymers the presence of a liquid may influence the ultra-thin properties. Here, we introduce a new method, freestanding tensile tester to directly measure the uniaxial stress-strain response of freestanding polymer thin films. Using polystyrene thin films, with thickness 30 nm-100 nm, we observe and quantify large strain deformation mechanisms, as well as yield stress and elastic moduli, and compare these results to the liquid supported measurements. We find that the liquid acts as a craze stabilizer for polystyrene thin films which leads to lower strains in the freestanding method compared to the liquid supported method. These results provide new fundamental insights into how the surface interactions can alter polymer behavior in thin confined polymer films.

Directly measuring the uniaxial stress-strain response of freestanding ultra-thin glassy polymer films

2019 Fall National Meeting

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