Light and strain responsive polymeric materials

Stimuli-responsive polymers have garnered significant attention for their ability to undergo reversible changes in response to external cues. This thesis contributes to the development of smart materials by the covalent incorporation of molecular switches into two categories of polymers: linear elastomers and crosslinked thermoresponsive polymers, known as hydrogels.

In thermoresponsive hydrogels, two types of azobenzene derivatives were co-polymerized to add light as a remote stimulus for controlling the phase transition behaviour. The first type is a hydrophobic azobenzene which can modulate the phase transition temperature by 6 °C and induce light-driven hydrophilicity in the network. This hydrogel formulation was further used to develop precise photo-actuating micropillars for cell sorting applications. The second type, an amphiphilic azobenzene resulted in broadening of the phase transition temperature enabling super swelling and super deswelling in the hydrogels. Through a combination of synthesis, characterization, and functional analyses, the work compiled in this thesis advances the understanding of photo-, mechano- and thermos-sensitive polymeric systems (linear and crosslinked) and paves the way for their future applications in responsive and adaptive materials.

This thesis focuses on processing spiropyran functionalized elastomers into mechanchromic microfibers. The strategy of polymer blending is used to stabilize the micro-fibers, improving their durability, functionality, and reliability for advanced applications. Mechanochromic polymers exhibit color changes in response to mechanical stimuli, offering potential applications in stress sensing and smart materials. Additionally, the covalent integration of diazocine units into polymers via an atom transfer radical polymerization (ATRP) led to photochromic elastomers. The significant changes in the π-systems, resulting in color and size changes in the respective molecular switches, were utilized for developing mechano- and photo-sensitive smart materials.