Surface and Biocidal Properties of Gemini Cationic Surfactants Based on Propoxylated 1,6-Diaminohexane and Alkyl Bromides

Summary: Two new classes of gemini cationic surfactants— hexanediyl-1,6-bis[(isopropylol) alkylammonium] dibromide {in the abbreviation form: CnC6Cn[iPr-OH] and CnC6Cn[iPr- OH]2; alkyl: CnH2n + 1 with n = 9, 10, 12 and 14}—have been synthesized by interaction of alkyl bromides with N,N0-di- (isopropylol)-1,6-diaminohexane and N,N,N0,N0-tetra-(isopropylol)- 1,6-diaminohexane. The surface tension, electrical conductivity, and dynamic light scattering (DLS) techniques were used to investigate the aggregation properties of the gemini cationic surfactants in aqueous solution. The formation of critical aggregates at two concentrations in an aqueous solution from obtained gemini cationic surfactants were determined via the tensiometric method. Thus, these gemini cationic surfactants start to form aggregates at concentrations well below their critical micelle concentrations (CMC). The surface properties and the binding degree (β) of the opposite ion were tested against the length of the surfactant hydrocarbon chain and the number of the isopropylol groups in the head group. By applying the DLS technique, it was explored that how the number of isopropylol groups in gemini cationic surfactants with C12H25 chain affects the sizes of micelles at concentrations greater than CMC. It was discovered that the obtained gemini cationic surfactants have a biocidal character.