Photomechanics of polymers and its applications to active structures and additive manufacturing
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Photopolymer is responsive to ultraviolet or visible light and changes its properties for various applications such as actuation, shape morphing and additive manufacturing. Compared to thermal polymerization, photopolymerization has the similar propagation, termination and chain transfer steps while the initiation step is photoinduced. The objectives of this dissertation research are to study the photomechanics of polymers including light activated polymer and two stage reactive polymer, and explore their applications in photoinduced actuation, material property evolutions, and 3D printing of porous polymers. For the photomechanical study of light activated polymers, a constitutive model based on phase evolution theory is developed to capture the photoinduced stress relaxation. A laminated composite is designed to achieve photo-induced bending in a free-standing state. For two-stage reactive polymers, a photo-thermoviscoelastic model is developed to describe the significant property change during the 2nd stage evolution and the photoinduced viscoelasticity observed in the experiments. Moreover, various photopolymers are mixed with salt particulates to 3D print a polymer-salt composite which can be immersed in water to leach salts and generate pores. Porous polymer structures with 74% porosity can be 3D printed with the advantages of self-supporting, biocompatibility and shape memory effect. The porous parts can be infiltrated by secondary materials to improve the strength or become conductive, and be metalized by electroless nickel plating. In summary, this dissertation presents the study of light interactions with polymers focusing on actuation, property control and 3D printing of functional porous polymer.