Backbone vs. side-chain: two light-degradable polyurethanes based on 6-nitropiperonal

Stimuli-degradable polymers are regarded as interesting materials for various applications like patterning or drug delivery. In particular, light as a trigger received a lot of attention due to the possibility of adjusting wavelength, light intensity and irradiation time, which leads to a precise and controlled application. In this study, we report the synthesis of two novel light-degradable polyurethanes which are based on 6-nitropiperonal and differ in the implementation of the light-cleavable unit. Degradation of these backbone- or side-chain-cleavable polymers was analyzed by UV/Vis spectroscopy and SEC. While both polymers showed rapid decomposition in solution, differences in the degradation rates were observed dependent on the incorporation site of the light-cleavable unit. Furthermore, nanoparticles were fabricated and characterized by photon correlation spectroscopy as well as scanning electron microscopy proving the processability of the polymers for potential application as, e.g., a controlled release system.