Synthesis of Polyazobenzenes Exhibiting Photoisomerization and Liquid Crystallinity

Bach-Type Polycondensation with the Aid of Hemoglobin as an Oxygen Supplier, and Synthetic/Bio-Composite

We developed a new Bach-type reaction in the presence of oxy-hemoglobin as an oxygen supplier to synthesize polyazobenzene by traditional Bach reaction. The resultant product is a form of polymeric dye/hemoglobin copolymer. The advantage of this research is that it involves a new reaction using the function of biomolecules, as well as the formation of plastics and biomaterials. The bio-based material may have good affinity with life forms, which may lead to applications in medical science.

Synthesis and Self-Assembly of Multistimulus-Responsive Azobenzene-Containing Diblock Copolymer through RAFT Polymerization

This paper gathered studies on multistimulus-responsive sensing and self-assembly behavior of a novel amphiphilic diblock copolymer through a two-step reverse addition-fragmentation transfer (RAFT) polymerization technique. N-Isopropylacrylamide (NIPAM) macromolecular chain transfer agent and diblock copolymer (poly(NIPAM-b-Azo)) were discovered to have moderate thermal decomposition temperatures of 351.8 and 370.8 °C, respectively, indicating that their thermal stability was enhanced because of the azobenzene segments incorporated into the block copolymer. The diblock copolymer was determined to exhibit a lower critical solution temperature of 34.4 °C. Poly(NIPAM-b-Azo) demonstrated a higher photoisomerization rate constant (kt = 0.1295 s-1) than the Azo monomer did (kt = 0.088 s-1). When ultraviolet (UV) irradiation was applied, the intensity of fluorescence gradually increased, suggesting that UV irradiation enhanced the fluorescence of self-assembled cis-isomers of azobenzene. Morphological aggregates before and after UV irradiation are shown in scanning electron microscopy (SEM) and dynamic light scattering (DLS) analyses of the diblock copolymer. We employed photoluminescence titrations to reveal that the diblock copolymer was highly sensitive toward Ru3+ and Ba2+, as was indicated by the crown ether acting as a recognition moiety between azobenzene units. Micellar aggregates were formed in the polymer aqueous solution through dissolution; their mean diameters were approximately 205.8 and 364.6 nm at temperatures of 25.0 and 40.0 °C, respectively. Our findings contribute to research on photoresponsive and chemosensory polymer material developments.