Synthesis And Self-assembly Of Phtostimulus-response Oligomers

Stimulation-responsive materials are very important for further development in many research fields,including drug delivery and sensor fields.More specifically,stimulation-responsive materials have unique applications,such as real-time imaging.Compared with other stimulus responses,light has unique advantages.It can determine selectivity by different wavelengths.It is easy to adjust energy without interference from other reagents.In this thesis,oligomers with spiropyran were designed and synthesized.The spiropyran unit has the properties of reversible adjustable ring opening and closed loop under ultraviolet/visible light.Self-assembly of target molecules into vesicles is available in methanol solution under visible light.When irradiated by ultraviolet light,the hydrophobic spiropyran(SP)isomer becomes a hydrophilic mercyanine(MC)isomer with longer conjugated unit The increase of hydrophilicity in the system results in the formation of smaller micelles,while the color of the solution changes from yellow to red.While,increasing temperature can be closed back to(SP)isomers.When the target molecule dissolves in water,the ring opening and closed loop property of the target molecule does not change under ultraviolet light,but when the heating temperature is raised,the SP isomer opens to form MC isomer.With the increasing of the temperature,the degree of ring opening increases,but when the temperature rises higher,the MC isomer begins to close-loop back to SP isomer.In this thesis,rod-coil amphiphilic molecules are also designed and synthesized,which are composed of an aromatic segment b'ased on a azobenzene and biphenyl units and hydrophilic polyethylene oxide chains.These molecules self-assemble into lamellar and two-dimensional columnar nanostructures in bulk state.In aqueous solution,these molecules self assemble into nanosheets,long fibers and nanosheets,large sheets,depending on the chain length of the molecules.Notably,Uv/vis illumination resulted in trans/cis isomerism of azobenzene unit of rod-coil molecules.In the bulk,these molecules have no the light response of the liquid crystal phase,because the liquid crystal phase transformation temperature is higher than the tran/cis isomer critical temperature.In aqueous solution,trans/cis isomerism of azobenzene unit induced nanostructures turming into fibers,short fibers and nano-sheets,sheets.These result reveals that trans/cis isomerism of azobenzene could be used as a external stimulus for driving force of amphiphilic molecular self-assembling systems to build various stimuli-responsive nanostructures.