Download or read book Characterization of Photo-induced Mechanical Responses in Azobenzene Polymers written by Zahid Mahimwalla and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "A cantilever based sensor system was adapted to characterize the photo-mechanical effect in thin films of azobenzene based polymers coated on silicon and mica cantilevers. The photomechanical effect is defined as a reversible molecular shape change upon absorption of light, resulting in a significant mechanical macroscopic deformation of the host material. The sensor was used to calculate cantilever bending, changes in surface stress, photo-mechanical energy, efficiency, and energy per unit volume for the polymers PDR1A, PDR13A and PMMA-co-PDR1A based on DR1 and DR12 dyes. The study demonstrated fast and significant cantilever bending as well as a robust, repeatable, and measurable photo-mechanical effect for the polymers studied. PDR1A exerted the largest forces and PMMA-co-PDR1A the greatest efficiency. This exhibits the ability of these thin polymer layers to act as strong light-driven 'artificial muscles' for larger mechanical systems, and the utility of the cantilever sensor platform for quantitative characterization of the photomechanical effect of azobenzene based polymers.While micron-scale surface mass transport and formation of surface relief gratings in azobenzene polymers is a well-known phenomenon, a complete understanding of the underlying mechanism has yet to be achieved. Nanoindentation experiments were conducted to elucidate the changes in mechanical properties of PDR1A, a well-known covalent side-chain azo polymer and P4VP(DY7)0.5, a hydrogen-bonded polymer-azobenzene complex, under irradiation. Material creep was characterized by calculation of the strain rate sensitivity m, of the two polymers for the dark and illuminated states. The experiments show a significant change in material creep between the dark and illuminated states of both materials. The measured strain rate sensitivity m increases from 0.021 to 0.038 (81%) for PDR1A and 0.086 to 0.192 (123%) for P4VP(DY7)0.5 between the dark and illuminated states respectively. The correlation of experimental data describing photo-induced softening to the structure-property relationships of the two materials and their implications to understanding surface mass transport in azobenzene based materials is discussed." --