Smart materials based on azo dyes: from light-responsive adhesives to artificial muscles

Photoswitches, such as azobenzene dyes and their analogues, if combined with polymeric materials are a powerful tool to develop a plethora of light responsive materials. Indeed, the isomerization of such dyes can be triggered by specific irradiation leading to material property variation at macroscopic level. In this thesis, we developed different materials through the integration of novel photoswitches, specifically arylazoisoxazoles (AIZs), into polymer matrices, enabling smart systems that dynamically respond to light for different applications ranging from photoresponsive adhesives to drug delivery and soft robotics. The initial part of this work focuses on the synthesis and spectroscopic characterization of a small library of azo molecules, examining the effects of structural variations (such as the introduction of heterocyclic rings or the presence of phenol groups) on their photoswitching efficiency and thermal stability. These insights set the foundation for material systems where extended stability in the cis-state is advantageous. Then, a series of different azopolymers were developed, including linear or crosslinked polymers and supramolecular modified block-copolymers. In particular, we described photoresponsive adhesives prepared by free-radical polymerization and capable of rapid and reversible light-induced adhesion changes, allowing for controlled, temporary bonding in reconfigurable surfaces. Additionally, through RAFT-PISA techniques, micelles incorporating AIZ-thymine photoswitches were synthesized to enable light-triggered release mechanisms, ideal for controlled drug delivery applications. In the last part the thesis examines 3D-printed liquid crystalline elastomers (LCEs) that exhibit stimuli driven shape-changing behavior. By leveraging customizable alignment patterns, these LCEs demonstrated rapid, reversible deformations under both light and thermal stimuli, suitable for applications in adaptive photonic systems and soft robotics. The research emphasizes the versatility of photoswitches in various polymer architectures, showcasing how precisely engineered materials can achieve tunable, responsive functionalities. This work not only enhances the understanding of photoresponsive systems but also opens pathways for innovative applications, with future potential in biocompatible designs and improved material architectures for advanced technological fields.