Photoresponsive PLA-based Smart Materials via Physical and Reactive Blending with Azobenzene Dyes

The development of photoresponsive bioplastics offers exciting opportunities for sustainable, functional materials in advanced applications such as sensors, packaging, and biomedical devices. In this work, poly(lactic acid) (PLA) was combined with 4-phenylazophenol (AZO), an azobenzene derivative, to produce light-responsive polymers via two strategies: physical blending and reactive blending. Physical blends exploited hydrogen bonding between PLA and AZO, while reactive blending employed dicumyl peroxide to incorporate AZO into the PLA backbone, preventing dye migration. The influence of PLA morphology, amorphous vs. semicrystalline, on AZO’s optical response and diffusion was systematically investigated for the physical blends. UV-vis spectroscopy confirmed efficient trans-cis photoisomerization and indicated higher trans-isomer absorbance in semicrystalline matrices, although thermal back-isomerization kinetics were largely unaffected by crystallinity. Migration studies showed significantly reduced AZO diffusion in semicrystalline matrices and complete suppression in reactive systems, as confirmed by spectroscopy and visual inspection. Overall, reactive blending enabled the production of stable, non-leaching, photoactive PLA materials without compromising responsiveness, offering a scalable approach for the synthesis of functional bioplastics.