Azopolyesters with Intrinsic Crystallinity and Photoswitchable Reversible Solid-to-Liquid Transitions

Area of Science:

• Polymer Chemistry
• Materials Science
• Photochemistry

Background:

• Azobenzene-containing polymers are known for photoresponsive properties.
• Controlling polymer properties like crystallinity and phase transitions is crucial for advanced materials.

Purpose of the Study:

• To synthesize novel azobenzene-based polyesters with intrinsic crystallinity.
• To investigate the photoinduced reversible solid-to-liquid transition behavior of these azopolyesters.
• To explore their application as light-switchable adhesives.

Main Methods:

• Copolymerization of azobenzene-based epoxides with cyclic anhydrides.
• Characterization of polyester properties including melting temperature (Tm) and glass transition temperature (Tg).
• Investigation of photoisomerization (trans-cis) induced by UV light and its effect on material state and adhesion.

Main Results:

• Synthesized azopolyesters with Tm ranging from 51-251°C, influenced by side-chain length and stereoregularity.
• Demonstrated reversible solid-to-liquid transitions upon light irradiation; solids (trans) transition to liquids (cis) with Tg below -20°C.
• Achieved light-controlled adhesion strengths between 0.73-0.89 MPa (trans) and ~0.1 MPa (cis) for various substrates.

Conclusions:

• Azobenzene-based polyesters offer tunable crystallinity and photoresponsive solid-to-liquid transitions.
• These materials function as effective light-switchable adhesives, allowing precise control over adhesion via UV light.
• The study highlights the potential of azopolymers in developing advanced photoresponsive materials and smart adhesives.