Changing Self-Assembly Through Degradation: Phenyl Vinyl Ketone Polymer Nanoparticles Under Light.

Photodegradable nanoparticles with sphere, worm, and vesicle morphologies were synthesized following polymerization induced self-assembly (PISA), incorporating a photoresponsive phenyl vinyl ketone (PVK) block and a nonphoto responsive 2-hydroxypropyl methacrylamide (HPMA) block. The photodegradation of nanoparticles under UV revealed that the initial shapes of sphere and vesicle particles are retained even until 7 h and after 24 h of photo-induced degradation, respectively, despite a significant reduction in molecular weight (M_n). This could be due to the assembly of degraded PVK fragments in the hydrophobic region, maintaining the relative hydrophilic to hydrophobic ratio. However, worm nanoparticles exhibited a fast morphology reversal after 2 min of degradation, yielding sphere nanoparticles. Therefore, photo responsive PVK nanoparticles with morphology and conversion-dependent degradation behavior were explored. Furthermore, undegraded and degraded nanoparticle coatings exhibited different surface properties, determined by contact angle measurements, with both morphology and degradation impacting the surface properties. Finally, the PVK nanoparticles could encapsulate molecules and release them upon degradation. Therefore, this study can ultimately be applied to numerous fields due to the potential uses of degradable polymers in various material systems, especially for the controlled release of agrochemicals, cleaning agents, or antifungal agents, as well as to enable surface modifications upon degradation.