New gemini surfactants with two azobenzene groups controlled by light irradiation

Abstract

The synthesis of N,N’-bis (4-alkylazobenzene-4-oxy-2-hydroxypropyl)-N,N,N’,N’-tetramethylethylene diammonium methylsulphate (qDAZDA-n series, n = 0, 2, 4, and 8), a new type of symmetric gemini light-sensitive cationic surfactants, has been achieved. The CMC range was extremely low at 5.23–2.17 × 10−4 mN m−1 when in the trans form, and 1.91 × 10−3–4.91 × 10−4 mN m−1 as mixtures with 92% cis isomer. The synthesis was designed to be conducted under mild conditions, such as atmospheric pressure, temperatures not exceeding 100 °C, and solvents that can be easily removed, thus showing promise for industrial applications. Upon exposure to UV light, 92.5% of the trans-qDAZDA-n series underwent conversion to the cis form, and upon exposure to visible light, 69.3–77.3% of the compound was transformed back to the trans form. The study conducted contact angle measurements on a hydrophilic media to investigate the wettability of the surfactants. Tests were conducted on the properties of the synthesized surfactants, and a comparison was made with two commonly used commercial surfactants, sodium lauryl ether sulfate (SLES-3) and dodecyl benzene sulfonate (DBS).