Study On The Photosensitivity Of Quaternary Ammonium Salt Cationic Surfactant And Carboxylate Additive Mixed Systems

Light-responsive micellar system is one of the research hotspots of smart micellar systems in recent years.In this thesis,we try to prepare light-responsive micellar systems by green anionic surfactants,（green）cationic surfactants and green additives.The effects of molecular structure,mixed molar ratio,total surfactant molality and mixed additives on the formation and transition of light-responsive micelles have been investigated.The UV light-responsive behaviors of micellar systems have been systematically studied by some technological means,such as ¹H nuclear magnetic resonance（¹H-NMR）,transmission electron microscopy（TEM）,dynamic rheology and dynamic light scattering（DLS）.（1）An ester-containing gemini quaternary ammonium surfactant,N,N’-bis（2-（dodecanoyloxy）ethyl）-N,N,N’,N’-tetramethyl-1,3-propane diammonium dibromide(C₁₂DEG₃),with trans-ortho-methoxycinnamate（trans-Na OMCA）or（and）trans-cinnamate（trans-Na CA）as photosensitive additives,has been used to construct light-responsive wormlike micellar systems.The cationic C₁₂DEG₃and some anionic surfactants with good biocompatibility and good biodegradability have been used to prepared cationic/anionic surfactant mixed systems,the surfactant mixed systems with trans-Na CA or（and）trans-Na OMCA as additives have also been used to construct light-responsive wormlike micellar systems.Our experimental results indicated that the light-responsive wormlike micellar systems based on the cationic/anionic surfactants and mixed photosensitive additives with appropriate concentration and molar ratio show higher photo-responsive ability than those based on the single C₁₂DEG₃.The UV-light-induced trans-cis isomerization of Na OMCA or Na CA leads to the microstructural transition from wormlike micelles to short rodlike micelles,resulting in reduction in the shear viscosity by 3 to 4 orders of magnitude.In addition,the total surfactant molality m _T,the molar ratio between anionic and cationic surfactant MR_A/C,and the surfactant molecular structure play important roles in the photo-responsive ability of the mixed systems.（2）In the C₁₂DEG₃/trans-Na OMCA/H₂O mixed systems,part of trans-Na OMCA has been replaced by sodium salicylate（Na Sal）to construct light-responsive micellar systems with better photosensitivity.The experimental results show that when the surfactant concentration is reduced to m _T=9 mmol·kg^-1,the viscosity of the C₁₂DEG₃/Na Sal/trans-Na OMCA/H₂O mixed system can still be reduced by 3 orders of magnitude after UV irradiation.In addition,keeping m _Tunchanged,micelles with stronger light-responsive ability can be obtained by adjusting MR_A/C.In addition,when adding N-lauroylsarcosinate（SLS）,keeping m _T=9 mmol·kg^-1and adjusting MR_A/C=2.0/98.0,the system viscosity can reach 28.8 Pa·s(shear rate is 0.075 s^-1),the viscosity drops to 0.010 Pa·s after UV irradiation for 10 min,and the system viscosity drops by three orders of magnitude,showing good photosensitivity.（3）In the light-responsive micellar systems constructed by cetyltrimethylammonium bromide（CTAB）and trans-Na OMCA or trans-Na CA,keeping the total surfactant molality m _Tunchanged,part of CTAB has been replaced by the green surfactant N（α）-palmitoyl-lysine methyl ester（PLM）to construct new light-responsive micellar systems.The addition of trans-Na OMCA or trans-Na CA into the aqueous mixed solution of PLM and CTAB induces the formation of wormlike micelles.After UV light irradiation,both the viscosities of CTAB/PLM/trans-Na CA/H₂O mixed systems and the viscosities of CTAB/PLM/trans-Na OMCA/H₂O mixed systems decrease by 4 orders of magnitude,but the two mixed systems have their own characteristics.The CTAB/PLM/trans-Na OMCA/H₂O mixed systems show higher ultraviolet（UV）photo-responsive efficiency,and ultraviolet light irradiation for 20min leads to significant reduction in the viscosities of the systems.While,the CTAB/PLM/trans-Na CA/H₂O mixed systems can self-assemble to form gels with larger viscosity and show strong light-responsive ability,but it requires several hours of UV light irradiation time to induce significant reduction in viscosity.The CTAB/PLM/trans-Na CA/trans-Na OMCA/H₂O mixed systems constructed by mixed photosensitive additives have the advantages of both the two photosensitive additives.