Synthesis and evaluation of new imidazolium‐based aromatic ether functionalized cationic mono and gemini surfactants

Abstract

Synthesis of a novel series of imidazolium-based surfactants, [(ROArCH 2 MIm)Br] with aromatic ether functionalized hydrophobic tail of varying chain lengths and also their gemini counterparts were conducted in the present work. Synthesis involves initial conversion of 4-hydroxy benzoic acid to its methyl ester followed by its O-alkylation with long chain fatty alcohols, which was subsequently reduced and brominated to get 4-alkyloxy benzyl bromide. For the synthesis of monocationic surfactant, 4-alkyloxy benzyl bromide is quaternized with N-methylimidazole. Gemini surfactants are synthesized by initial coupling of imidazole to 4-alkyloxy benzyl bromide followed by its quaternization with dibromoalkane. The surface properties of all the synthesized surfactants were determined using surface tensiometry. Within the same homologous series, expected decrease in critical micelle concentration (cmc) with the increase in hydrophobicity was observed for shorter chain homologs. However, the deviation in cmc value from regularity was observed when the number of carbon atoms in the hydrophobic chain exceeded a certain number. The cmc values of the geminis were found to be remarkably low compared to their monomeric counterparts.

Heterocyclic Cationic Gemini Surfactants: A Comparative Overview of Their Synthesis, Self‐assembling, Physicochemical, and Biological Properties

“…Heterocyclic cationic GS such as pyrolidinium, imidazolium, or pyridinium are also accessible using these general alkylation strategies, but the reduced nucleophilicity of nitrogen‐containing heterocycles requires longer reaction times and generate smaller final yields as compared with ammonium GS. For example, the pyridinium GS with a tetramethylene spacer 15 has been synthesized from 1,4‐dibromobutane 14 and α‐alkyl pyridine 13 in ethanolic medium at reflux (Scheme a).…”

Effect of aromatic ring on surface and self‐assembly properties of synthesized heterocyclic‐based surfactants

“…Accordingly, heterocyclic‐based aromatic or aliphatic ether bridged cationic surfactants were synthesized. Imidazole‐based aromatic ether conjugated cationic surfactant published earlier has not been studied thoroughly for their self‐assembly properties (Sunitha et al, 2011). This has become the basis of the present study, wherein following the same protocol morpholine‐based aromatic ether conjugated surfactant also synthesized and a comparison was drawn to study the effect of type of heterocyclic moiety in the head group region.…”

“…The aromatic ether bridged surfactant with heterocyclic (imidazole and morpholine) in the head group region was synthesized according to the procedure reported by Sunitha et al (2011). A schematic diagram depicting the synthesis of both aromatic bridged surfactants is shown in Scheme 1.…”

“…Synthetic design of surfactant molecule was made in a manner to introduce variations by incorporation of imidazole and morpholine in the head group and also by inclusion and exclusion of a bridged phenyl ring, keeping the chain length fixed to 12 carbons. Aromatic ether bridged imidazolium ( Ar‐I ) or morpholinium ( Ar‐M ) surfactant was synthesized as per the procedure reported in the literature (Sunitha et al, 2011). Aliphatic ether bridged imidazolium ( Al‐I ) or morpholinium ( Al‐M ) surfactant has not been reported earlier and has been synthesized for the first time.…”

Ionic Liquids and Polymeric Ionic Liquids as Stimuli-Responsive Functional Materials

“…Bromide and tetrafluoroborate salts were prepared, and the resulting liquid-crystalline phases were characterized by x-ray scattering and polarized light microscopy. Mono and Gemini imidazolium-based aromatic ether cationic surfactants have been prepared using 4-hydroxy benzoic acid [39], where the benzoic acid is converted to the methyl ester followed by O-alkylation with long-chain alcohols and by reduction and bromination to yield 4-alkoxy benzyl bromides. N-Methylimidazole is then quaternized with this benzyl bromide to obtain the mono-surfactants.…”