Azo Polymer Microstructure Of Light Regulation And Solution Self-assembly Behavior Research

Stimuli responsive polymeric materials can respond to external stimuli such as thermal, light, pH, mechanic etc. Recently, they are widely applied in every aspect of our lives and industrial manufacturing. Among these external stimuli, light is focused because it has the advantages of faraway control and pollution-free. The azobenzene molecule is often invovled into the light-responsive polymeric materials due to its photoisomerization:in solid-phase system, the crosslinked liquid crystal polymers containing the azobenzene moiety have the property of photoinduced deformarion; in liquid-phase system, the aggregates formed by the amphiphilic diblock copolymers containing the azobenzene moiety have the photoresponsive behavior.Herein, in solid-phase system, the micro structure formed by the crosslinked liquid crystal polymers containing azobenzene moiety was fabricated by replica molding method, including the mirco array structure and inverse opal structure. The pillars of the micro array structure would take place photoinduced deformation when irradiated by UV light due to the photoisomeization of the azobenzene moiety, inducing the order of the micro array structure decreased. As the period of the micro array was about1μm, The light at the near wavelength reflected by the micro array structure exhibited a reflection peak due to the interference enhancement of the light. And the reflection peak showed the reversible on/off switching behavior when irradiated by UV/visible light. Moreover, the wavelength of the reflection peak could be modulated by the angle of incident light and the time of the on-off switching behavior could be controlled by the intensity of the UV/visible light irradiation. So it has potential application in light-controlled micro actuators.When the inverse opal structure was under UV light irradiation, the crosslinked liquid crystal polymers containing azobenzene moiety would take place photoinduced deformation. It would cause the order of the structure decreased and the volume fraction of the materials in the inverse opal structure changed. Thus the bandgap of the inverse opal structure was decreased and blue-shifted. However, with the irradiation of the visible light, the recovery of the photoinduced deformation would take place at all directions according to the unaligned liquid crystal molecules. Thus, the order of the inverse opal structure couldn’t be recovered, nor did the bandgap.In liquid-phase system, the amphiphilc diblock copolymer containing azotolane (PEO-b-PMA9ABT) was synthesized through atomic transfer radical polymerization (ATRP). The reversible photoisomerization of the copolymer could be realized by the irradiation of visible light at wavelength of405nm and530nm. The aggregates were prepared in THF/H2O mixture solution. TEM image shows the morphology of the aggregates is sphere micelle. When irradiated with light of405nm, the irregular micelles occur and the size of the micelles decrease. Moreover, the irregular micelles gather together. After the irradiation of the530nm light, the micelles recover to the initial state. Furthermore, the Nile Red encapsulated in the micelles can be controlled released under the visible light irradiation. So it has potential applications in the field of light-controlled encapsulation releasing.