Nanoscopic mechanical tests for characterizing forces during UVinitiated mass transport in photosensitive polymer films

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We aim at characterizing the thermochemical forces emerging during topography changes of azo-modified photosensitive physisorbed polymer films and brush systems by looking at the mechanical response of thin adsorbed gold layers. Azo-modified photosensitive polymers offer the interesting possibility to reshape bulk polymers and thin films by UV-irradiation while being in the solid glassy state. The polymer undergoes considerable mass transport during domain formation of chromophores. Our comparative studies on physisorbed photosensitive thin films and brush systems indicate, that in brushes with their restricted dynamics of single chains show a much stronger response. The forces inscribing a topographical pattern into a thin film are hard to assess experimentally directly. Our results, however, indicate that they can give rise to strong deformation on thin adsorbed gold layers. In this work, we are going to employ, along with AFM imaging, two new methods, confocal Raman and IR-nearfield techniques, for spatially resolving the composition of the hybrid gold-polymer system and quantitatively characterize the mechanical work that can be done by a film on gold layers of varying thickness. In the following, we shall also attempt to characterize the chemical composition of the polymer film itself and arrive at a detailed molecular picture of the origin of inscribing forces.