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• The photo-sensitive micellar systems have improved biodegradability and less toxicity. • Photo-responsive systems based on mixed cationic/anionic surfactants are superior. • Mixed photo-sensitive additives have the advantages of both the constituent additives. • Photo-responsive systems are based on low concentrations of surfactants and additives. A method to construct photo-responsive wormlike micellar systems with high photo-responsive efficiency and strong photo-responsive ability and reduced impact on the environment by mixed cationic/anionic surfactants and mixed photo-sensitive additives has been proposed. For this purpose, a cleavable cationic ester-containing gemini surfactant, N , N '-bis(2-(dodecanoyloxy)ethyl)- N , N , N ', N '-tetramethyl-1,3-propane diammonium dibromide (C 12 DEG 3), and five anionic biocompatible carboxylate surfactants, have been selected. The mixed photo-sensitive additives are composed of sodium trans -ortho-methoxycinnamate (trans -NaOMCA) and sodium trans -cinnamate (trans -NaCA). The mixed cationic/anionic surfactants are superior to the single cationic surfactant C 12 DEG 3 in constructing UV light-responsive wormlike micellar systems due to their stronger self-assembly ability. The molecular structure of anionic surfactant, such as the length of hydrophobic tail, the introduction of the N-methylated amide group between the hydrophobic tail and carboxylate headgroup, and the number of hydroxyl group in bile salts, is important factor influencing the self-assembly ability of the mixed systems. For single C 12 DEG 3 or the mixed cationic/anionic surfactants, the mixed photo-sensitive additives have the advantages of both trans -NaCA and trans -NaOMCA. The fast reaction rate of the trans -to- cis photoisomerization of NaOMCA leads to the high photo-responsive efficiency of the wormlike micellar systems. The addition of t rans -NaCA promotes the growth of wormlike micelles and leads to larger difference between viscosities before and after UV irradiation, demonstrating higher photo-responsive ability. The experimental results reveal that the UV light induced trans -to- cis isomerization of NaOMCA is the main reason inducing the microstructural transition from wormlike micelles to coexistence of spherical and short rodlike micelles and thus causing reduction in shear viscosities by 3–4 orders of magnitude. [ABSTRACT FROM AUTHOR]

Three ester-containing gemini surfactants (CmDEGs) 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 (C12DEG3) aqueous solution leads to a peak in zero-shear viscosity (η0) versus composition curve, and its further addition induces aqueous two-phase separation. For the C12DEG3/trans-NaOMCA/H2O mixed micellar systems, the UV responsiveness of significant decrease in η0 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, C12DEG3 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 C12DEG3/trans-NaOMCA/H2O mixed system on the UV-responsive behaviors was explored. In addition to UV-induced significant decrease in η0 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 η0 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 1H NMR spectra, molecular dynamics (MD) simulation, and molecular electrostatic potential (MEP) analysis. [ABSTRACT FROM AUTHOR]