Synthesis And Characterization Of Photo-responsive Giant Molecules And Preparation Of LB Films

Giant molecule is a kind of compound with high molecular weight and single molecular weight distribution.These unique properties arouse the interest of researchers.At present,the synthesis strategy of giant molecule is usually constructed by using nano-particles with definite chemical structure,such as polyoxometalate（POM）,polyhedral oligomeric silsesquioxane（POSS）,folding globulin and fullerenes(C₆₀).POSS not only has a clear chemical structure,but also has multi-functional side chain groups,which can further react with other chemical units.Therefore,POSS is widely used in the synthesis of giant molecules.Stimulus responsive materials have always been the focus of scientific research,among which azobenzene and its derivatives are typical photo-responsive materials with cis-trans structural transformation properties.Giant molecule with large molecular weight can be accurately synthesized by POSS-based multifunctional groups.The introduction of azobenzene derivatives into giant molecule can endue the photo-stimulus response of giant molecule,which provides a new idea for studying the self-assembly behavior of macromolecules and is conducive to the development of giant molecule.This topic takes this as the research objective,and the specific research content is as follows:1.Synthesis of photo-responsive giant moleculesTri Silanollsobutyl POSS（T₇-BPOSS）,vinyl-POSS（VPOSS）and 4’,4’-azodiazepine（ADA）as the building units,the giant molecules have been synthesized.The ~1H NMR,¹³H NMR,GPC curves and MOLDI-TOF tests have proved that the successfully synthesis of the giant molecules.2.Study on the photo-responsiveness and interface self-assembly of giant moleculesDissolve these giant molecules in N,N-dimethylformamide（DMF）and use UV-Vis absorption spectroscopy to study their photo-response behavior in solution.The results show that all giant molecules have obvious light responsiveness,giant molecules can quickly change from trans structure to cis structure under UV（365 nm）and they can change from cis structure to trans structure after dark treatment.In addition,due to the steric hindrance of POSS,the conversion rate of azobenzene from cis to trans after POSS particle is greatly reduced.By measuring the surface pressure-area（π-A）curves of the molecules in dark condition and under UV radiation,it can be seen that giant molecules under UV have significantly different interface behavior compared with in dark condition.Brewster angle microscope（BAM）in-situ monitoring showed that all photo-responsive molecules can form a stable monomolecular film at the air-water interface.3.Preparation of LB films and its photo-responseThe Langmuir-Blodgett（LB）films of photo-responsive giant molecules are prepared by LB films analyzer.Preliminarily confirm whether the giant molecular monolayers are transferred from the air-water interface to the glass substrate through a contact angle analyzer.Use AFM to further determine whether the LB film is successfully prepared and study the surface morphology of the related LB films.Finally,the cis-trans structure transformation of photo-responsive giant molecules on solid matrix was confirmed by UV spectrophotometer.