Synthetic, Gelation And Photo-responsive Behaviour Of The Y-shape Azophenyl Hydrazide Derivatives

Azobenzene photochemical reactions are root factor that caused azobenzenederivatives intelligent light control self-assembly behavior and optical response. Asazobenzene photoisomerization performance,azobenzene groups introduced tocompounds and polymers which can let the compounds and polymers in the structure,configuration and conformation have some unpredictable changes under the opticalchanges, Supramolecular self-assembly process is the system that spontaneouslyassemble to form stable aggregates by hydrogen bonds, π-π interactions, van derWaals forces and ionic coordination bond.Combined with our previous work, wedesign and synthesis Y-shaped hydrazide derivatives based on hydrogen bonding andcontaining azobenzene group,and investigative the gelation and photo responsivebehaviour of them.The main results of work are as follows:1, This thesis design and synthesize a series of four kinds of Y-shaped elementscontaining azobenzene hydrazine derivative (Y-b8-OH, Y-n8-OH, Y-b8-OCH3andY-n8-OCH3).Molecular structure and purity of the product have been characterizedand confirmed by proton nuclear magnetic resonance spectroscopy, infraredabsorption spectroscopy and elemental analysis.2, By testing the performance of the gel of the four Y-shaped molecule, theY-b8-OH and Y-n8-OH molecules can not form the gel in an organic solvent.Y-b8-OCH3and Y-n8-OCH3molecules can form the gel in the nonpolar solvent,suchas chloroform,1.2-dichloroethane, benzene and toluene. Both ends of molecularchains is alkyl substituent in favor gel formation. Gel and thermal stability ofY-n8-OCH3are better than Y-b8-OCH3. This show that structure and length of the endalkyl chain also affect the gel, alkyl chains are the more hydrophobic,gel betterperformance. We use variable temperature1H NMR and IR absorption spectra proveadjacent molecules form a gel by intermolecular hydrogen bonds. The use of variabledensity and variable temperature UV spectra proved π-π interactions between the azobenzene molecules form J aggregates. The driving force of gel formation is N-Hand C=O of the hydrogen bonds, π-π interactions of the azobenzene and synergisticeffect of van der Waals forces between the alkyl chains.3, By UV absorption spectroscopy and nuclear magnetic resonance spectroscopyconfirmed Y-b8-OH and Y-n8-OH photoisomerization relatively weak. Y-b8-OCH3and Y-n8-OCH3chloroform gel has the photo responsive behavior. The gel showedgel-sol-gel transition under the irradiation by UV-light.By1H NMR, IR and UVabsorption spectroscopy test, we believe that photo response mechanism of gel ofY-b8-OCH3and Y-n8-OCH3is as follow: Under the irradiation by365nm UV,First,molecules have trans-cis transition in the solution, in order to keep Balance ofconcentration trans-molecules in solution and gel, trans-aggregates depolymerize.When concentration cis-molecules in the solution reaches saturation, cis-aggregatesformed. Concentration cis-molecules in the solution begins to decrease, moleculeshave continued trans-cis transition in the solution. With the increase of UV irradiationtime, the fibers begin depolymerized, because hydrogen bonds of cis-aggregates islower than the trans-aggregates, the driving force is not sufficient to form a gel fiber,so gel transform to sol. Under the irradiation by455nm light,molecules have cis-transtransition in the solution, in order to keep Balance of concentration cis-molecules insolution and aggregates. Cis aggregates depolymerized and trans-aggregates formed.Then trans-aggregates build the fiber spatial structure,the gel-forming again. Whenthe solution is heating, cis and trans aggregates transformed molecular state insolution, molecules have cis-trans transition in the solution,, after cooling, trans fiberaggregate in the spatial structure and the gel formed.