Photoresponsive block copolymer: synthesis, characterization, and surface activity control

Area of Science:

• Polymer Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Amphiphilic block copolymers are crucial for developing smart materials with tunable properties.
• Controlling the surface activity and self-assembly of these copolymers using external stimuli like light and pH is an ongoing challenge.
• Photoresponsive chromophores integrated into polymer backbones offer potential for light-induced property modulation.

Purpose of the Study:

• To synthesize novel amphiphilic block copolymers incorporating a photoresponsive azochromophore.
• To investigate the light- and pH-induced control over the surface activity and self-assembly behavior of these copolymers.
• To establish a new method for reversible control of polymer transitions using external stimuli.

Main Methods:

• Synthesis of amphiphilic block copolymers via reversible addition-fragmentation chain-transfer (RAFT) polymerization.
• Characterization of copolymer self-assembly using static light scattering.
• Investigation of photoresponse and pH-dependent behavior through surface activity and structural transition studies.

Main Results:

• Synthesized copolymers self-assembled into vesicles (120-170 nm) above critical micelle concentration.
• Copolymers displayed surface activity at pH 7, becoming non-surface-active at acidic/alkaline pH.
• UV irradiation induced reversible transitions: surface activity loss and vesicle-to-micelle transformation due to azochromophore isomerization.

Conclusions:

• A novel method for light- and pH-controlled surface activity and self-assembly (vesicle/micelle) transitions was developed.
• The reversible nature of these transitions offers potential for advanced responsive materials.
• Integration of azobenzene chromophores and betaine monomers provides a versatile platform for smart polymer design.