Self-assembly Of Photo-thermal Dual Stimuli-responsive Rod-coil Oligomers

Polymers that have the ability to respond to external stimuli are called smart polymers or stimuli-responsive polymers.These polymers can respond to stimuli by changing color,light transmission capacity,conductivity,shape,wettability,and many other ways.And the degree of response of these polymers can be triggered and controlled by the intensity of the applied stimulus.The stimuli that cause polymer changes can be further divided into three categories:physical,chemical,and biological stimuli.Physical stimuli such as light,temperature,magnetism and electricity might change the chain dynamics(ie,energy levels);chemical stimuli modulate molecular interactions between the polymer and solvent molecules or between polymer chains to cause changes in the polymer.Biological stimulation corresponds to the actual function of the molecule,such as enzymatic reactions and receptor recognition.Along with the research go in deep,the multi-stimulus-responsive polymers containing two or more stimuli-responsive groups have caused widespread concern.Compared with single-stimulus-responsive polymers,multi-stimulus-responsive polymers can meet diversified application needs.In this paper,rigid rod strand molecules 6a,6b,6c composed of polyethylene oxide chain PEO with different degrees of polymerization in the rigid rod part containing azophenyl groups and flexible part were designed and synthesized by differential scanning calorimetry Instrument(DSC),polarized light microscope(POM)and small-angle X-ray(SAXS)diffraction to study the self-assembly in the bulk state.The difference in the PEO chain affects the melting point of the molecule,and the crystallinity decreases when the chain length increases.Molecule 6a is presumed to be a hexagonal columnar phase,molecule 6b is presumed to be a hexagonal columnar phase or a hexagonal close-packed phase,and molecule 6c forms a body-centered tetragonal phase.Subsequently,nuclear magnetic hydrogen spectroscopy(1H-NMR),ultraviolet-fluorescence spectroscopy(UV-FL),circular dichroism(CD),transmission electron microscopy(TEM),infrared spectroscopy(ATR-IR)were used to study the self-occurrence in aqueous solution The impact of assembly behavior.The experimental results show that the three target molecules self-assemble into a nanofiber structure,and the different flexible chains affect the assembly method.The isomerization of light under 3 65nm ultraviolet light weakens the π-π stacking effect and the nanofibers disappear.The low critical solution temperature(LCST)effect occurred in all three target molecules,and the LCST temperature corresponding to the different flexible chains also changed.It shows that the increase in temperature breaks the hydrogen bond between the flexible chains and waters and changes the assembly method.