| Smart materials are materials that exhibit field-coupled material behavior in response to external stimuli. One example is photomechanical materials that are able convert light energy into mechanical work. Light is a unique form of energy for adaptive structures. Light allows for time, wavelength, intensity, and polarization control. A material that can convert light to work would ideally take advantage of these characteristics. Azobenzene is a functional group that changes its molecular shape when exposed to certain wavelengths of light. This molecular shape change can cause an overall macroscopic shape change when the azobenzene is synthesized with a polymer network (azo-LCN). In this thesis, blocked stress measurements show that irradiated azo-LCN experience photochemical and thermomechanical stress. Total stress is dictated by thermomechnical stress at higher light intensities. Photomechanical stress a larger portion of total stress at lower light intensities. The thermomechanical stress occurs on the order of tenths of a second, whereas photomechanical stress is on the order of minutes to hours. A stronger understanding of the distinctions of photochemistry and heat is determined using solid state Nuclear Magnetic Resonance(NMR). NMR measurements show that heat alone does not cause a conformational change, but light irradiation causes a molecular structure change that is most likely associated with trans-cis isomerization. Isolating photochemical and thermal effects is an important step in functionalizng azo-LCN. The data in this work shows that decoupling may be possible by controlling time and intensity of the reactions. |
