Research On Light-responsive Supramolecular Self-assembled Elastomer And Its Mechanical/optical Properties

Developing polymers with specific functions by simplified yet efficient methods has always been an important objective in the research of polymer materials.This thesis focuses on the study of preparation and mechanical properties/photoresponsiveness of potentially photoresponsive elastomeric smart polymer prepared through molecular design and supramolecular interactions.Smart polymers can perceive external stimulus and respond accordingly.Photo-responsive polymers are smart polymers that are receiving wide research interests thanks to their eco-friendly,non-contact and controllable character.With the growing demand of smart devices,developing a flexible/elastomeric light response material would be conducive to the development of bionic and wearable devices.With the hope of developing a photo-responsive and elastomeric material through a rather simple preparation,a series of copolymers with different component ratios were synthesized from lauryl methacrylate(LMA)and 2-(diethylamino)ethyl methacrylate(DMAEMA)by free radical polymerization.The copolymers were quaternized by iodomethane,followed by supramolecular complexation with azobenzene small molecules to give rise to a potentially photo-responsive elastomer.As a proof-of-concept,the feasibility of the constructing components and ratio as well as their role of copolymer in the preparation of elastomeric network was first studied by selectively quaternizing PLMA-co-PDMAEMA in THF.An ionogel was obtained after quaternization of copolymer that can also turn into an elastomer with proper component ratio after evaporation of solvent.The tensile strength of this elastomer is 4 MPa,nearly 80 times higher than that of the copolymer before quaternization.The elastomer also shows excellent recover character,as evident by the identical results of mechanical property.Copolymers with various other ratios were also prepared and studied.A bifunctional azobenzene small molecules were introduced to this elastomer to achieve better mechanical property and photoresponsiveness.The azo molecules were bonded to the polymeric matrix through supramolecular interaction,acting as a coupling agent that transfer the mechanical force and photo-induced deformation.The tensile strength of the polymer was found to be improved after introduction of the bifunctional azo molecules.The tensile strength of quaternized elastomers with DMAEMA contents of 9.1%,6.2%and 4.6%increased by 11%,24%and 63%respectively.Moreover,mechanical property study of polymers with different monomer ratios shows that those with higher DMAEMA content have larger tensile strength,whereas their elongation at break decreases.In addition,the elastomeric polymers with azo are soluble in certain solvent,showing their excellent solvoplasticity and recyclability.Among them,when the content of DMAEMA is 4.6%,the flexibility is the best and the elongation at break is the highest.When the content of DMAEMA is 9.1 wt%,the tensile strength of the corresponding elastomer is the highest,whereas the elongation at break becomes smaller.leading to a reduced flexibility.The photoresponsiveness property of the material was studied by in its THF solution with a light of 405 nm.The trans-cis isomerization was observed after irradiation in 10 s.The cis-trans isomerization was also achieved by irradiation of the solution under visible light and after being heated for 30 min,the degree of recovery can reach 84%,showing the reversible photoresponsiveness of the product in solution.