Methodology for Measurement of Young's Modulus in Free-Standing Polymer Nanocomposite Thin Films

The mechanical properties of polymer nanocomposite thin films are central to their applications. Providing a non-contact and substrate-free thin film characterization method, bulgetests have many advantages to determine the mechanical behavior of free-standing thin films. In these tests the film is draped over a hole and subjected to a pressure differential which deforms, or bulges, it. In particular, bulge test allows for easy measurement of the Young's modulus, which characterizes the linear elastic response to applied strain or stress. Bulge tests furthermore are amenable to cyclic loading and time dependent creep measurements. However, previous work utilizing bulge tests used experimental approaches that either were slow in extracting film deflection data or did not directly measure the film deflection at each point in real time. In this thesis I discuss combining bulge tests with advanced, laser-scanning confocal microscopy to obtain the 3D profile of bulged films in less than 10 seconds. From the maximum height of the film deflection the Young's modulus can be extracted by approximating the bulge as a spherical cap. I apply this technique to obtain the Young's modulus of free-standing polymer nanocomposite (PNCs) thin films, which have the potential to be integrated in high-demand applications such as drug delivery, energy storage, novel packaging, and membrane filtration.