Antimicrobial Activity of Gemini Surfactants with Azapolymethylene Spacer.

A series of 21 azapolymethylene gemini surfactants were obtained. The synthesis of the title surfactants in one- or two-step reaction proceeds with good yields. The structure and the purity of the synthesized compounds were determined by 1H and 13C NMR, ESI-MS spectra, and elemental analysis. Moreover, 2D COSY, HMBC, and HSQC spectra were performed. The minimal inhibitory concentrations (MIC) of the synthesized compounds were determined against fungi: Candida albicans, Aspergillus niger, Penicillium chrysogenum and bacteria: Escherichia coli,Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis. Also, the critical micelle concentrations (CMC) were determined. The relationship between antimicrobial and surface activity and surfactant structure has been determined.

Gemini surfactant as multifunctional corrosion and biocorrosion inhibitors for mild steel.

Biocorrosion is an important type of corrosion which leads to economic losses across oil and gas industries, due to increased monitoring, maintenance, and a reduction in platform availability. Ideally, a chemical compound engineered to mitigate against biocorrosion would possess both antimicrobial properties, as well as efficient corrosion inhibition. Gemini surfactants have shown efficacy in both of these properties, however there still remains a lack of electrochemical information regarding biocorrosion inhibition. The inhibition of corrosion and biocorrosion, by cationic gemini surfactants, of carbon steel was investigated. The results showed that the inhibition efficiency of the gemini surfactants was high (consistently >95%), even at low concentrations. Gemini surfactants also showed strong antimicrobial activity, with a minimum inhibitory concentration (0.018 mM). Corrosion inhibition was investigated by electrochemical impedance spectroscopy (EIS) and linear polarisation resistance (LPR), with biocorrosion experiments carried out in an anaerobic environment. Surface morphology was analysed using scanning electron microscopy (SEM).

Biodegradability and aquatic toxicity of new cleavable betainate cationic oligomeric surfactants.

New cleavable oligomeric cationic surfactants containing ester groups susceptible to hydrolysis between the hydrocarbon tails and the hydrophilic moiety have been synthesized and their biodegradability and aquatic toxicity examined. Aerobic biodegradability was evaluated by applying a standard method for ready biodegradability, the CO2 Headspace test. Aquatic toxicity was assessed by means of the acute toxicity test with Daphnia. Cleavable oligomeric cationic surfactants undergo a significant biodegradation extent (31-52%) as compared to dimeric surfactants without ester groups that showed null degradation in previous works. However, they do not attain the threshold of ultimate degradation required (60%) to be classed as easily biodegradable chemicals. On the other hand, the introduction of cleavable groups in the surfactant hydrophobic chains reduces the toxic effects on the microorganisms responsible for degradation observed for conventional alkyl ammonium dimeric surfactants. Acute toxicity values of betainate cationic oligomeric surfactants to Daphnia magna, IC50-48 h, varies from 1.5 to 50 mg/L. Aquatic toxicity of oligomeric cationic surfactants depends on their hydrophobicity and increases regularly with the alkyl chain length. However, whether the surfactant is a dimeric or a trimeric betaine ester does not affect their acute toxicity to crustacean.