Photo-responsive Behaviour,Self-assembled Structures And Application Of Azobenzene Derivatives

Supramolecular Self-assembly system has become an important research direction in the field of materials.Depending on the property of the supramolecular Self-assembly system,supramolecular has a wide range of potential applications in many fields including drug release,light harvesting,templating reactions,molecular devices,environmental remediation,chemical sensors,liquid crystalline materials and optoelectronic materials.In this work,we systematically studied the photo-isomerization properties of supramolecular self-assembly system of azobenzene derivatives BNB-t4.The self-assembly behavior of BNB-t4 was controlled by introducing water,and the controlled mechanism was analyzed by Flory-Huggins solubility parameter.In addition,the efficient recovery of aromatic solvents,the efficient removal of toxic dyes and the releasing of molecular were realized by using the phase selective gelation properties of BNB-t4 molecules.Details are as follows:1.BNB-t4 can form a gel in the medium polar organic solvent.And the gel state has a good ability of photo-responsive.It was found that the transformation of self-assembly structures and the collapse of the BNB-t4 gel in chloroform could be realized with the irradiation of 365 nm UV light.The collapsing of gel mainly caused by the isomerization of BNB-t4 from trans-to cis-and the change of intermolecular forces induced by UV light.The change of gel-sol was corresponding to the morphological transformation from fiber to cube structure.2.The water regulation effects on the self-assembly structure transformation and self-assembly gel characteristics of BNB-t4 in organic-water mixtures have been systematically investigated at room temperature.The results indicated that BNB-t4 gelator can form opaque gels in aqueous-organic mixed solvents at the concentration of 2%(w/v)with the water content varying from 40% to 75%.The BNB-t4 gel at 60% water content showed the lowest MGC,the highest thermal stability and mechanical performance,and the most densely intertwined lamellar structure.XRD studies demonstrated that the xerogel of BNB-t4 gelator favors the lamellar structure.The driving force for self-assembly of BNB-t4 are mainly originats from the intermolecular H-bonding and the complementary cooperative balancing via π-π stacking as well as hydrophobic interactions.The model which was correlation with the Flory-Huggins parameter and depicted into four domains: solution,partial gel,gel and precipitate has been successfully established to predict the gelation behaviour of BNB-t4 in aqueous-organic mixed solvents.Thus,the simple regulation of supramolecular self-assembly behavior and the analysis of its controlled mechanism were realized.3.Organogelator BNB-t4 demonstrates remarkable gelation ability in many aromatic solvents and halohydrocarbons.It has been shown that the BNB-t4 phase-selective gelator(PSG)can remove various aromatic pollutants from aqueous solutions with high efficiency.Meanwhile,BNB-t4 PSG can also remove the toxic organic compounds from the contaminated water with a high efficiency of ~97%.Furthermore,the phase selection and phase transition properties together with the good thermo-stability and reversibility of the BNB-t4 PSG confer it the remarkable ability to efficiently collect and release some organic compounds.