UV-responsive micellar systems and aqueous two-phase systems based on cationic ester-containing gemini surfactant and sodium trans -ortho-methoxycinnamate

Three ester-containing gemini surfactants (C m DEG s ) were used to construct UV-responsive micellar systems with sodium trans - ortho -methoxycinnamate ( trans -NaOMCA) as photo-sensitive additive. The effect of tail-chain length and spacer chain length on the UV-responsive ability was preliminarily explored. Longer tail chain and shorter spacer chain are favorable factors for enhancing UV-responsive ability. The addition of trans -NaOMCA into N , N ′-bis(2-(dodecanoyloxy)ethyl)- N , N , N ′, N ′-tetramethyl-1,3-propane diammonium dibromide (C 12 DEG 3 ) aqueous solution leads to a peak in zero-shear viscosity ( η 0 ) versus composition curve, and its further addition induces aqueous two-phase separation. For the C 12 DEG 3 / trans -NaOMCA/H 2 O mixed micellar systems, the UV responsiveness of significant decrease in η 0 ascribes to microstructural transitions arising from the changes in counterion binding modes due to the trans - cis photoisomerization of NaOMCA. In comparison with the gemini surfactant 12-3-12, C 12 DEG 3 has ester groups introduced in its tail chains. The introduction of ester groups leads to a significant effect on enhancing the photo-responsive ability in viscosity decrease of the constructed UV-responsive micellar systems. Furthermore, the effect of the addition of an amino acid–based surfactant sodium lauroylglutamate (SLGlu) into the C 12 DEG 3 / trans -NaOMCA/H 2 O mixed system on the UV-responsive behaviors was explored. In addition to UV-induced significant decrease in η 0 and phase transition from aqueous two-phase systems (ATPS) to isotropic single-phase systems, the addition of SLGlu can also cause UV-induced increase in η 0 and lead to richer UV-induced phase transition behaviors. The reason leading to these differences due to the presence of SLGlu was discussed based on 1 H NMR spectra, molecular dynamics (MD) simulation, and molecular electrostatic potential (MEP) analysis. Graphical abstract