A new strategy to dissolve long-chain surfactants in water at low temperatures

Surfactants find widespread use in daily life for cleaning purposes and form a vital part of many industrial formulations. So far, their application has been limited to amphiphilic structures with relatively short alkyl chains (typically up to C14 or C16) due to the poor solubility of longer-chain homologues under relevant conditions. Here we introduce a concept that eventually allows octadecyl sulfates and carboxylates to be effectively solubilised in water at room temperature. Through synthesis of alkoxylated derivatives of choline - an abundant molecule of natural origin - we have designed a new class of counterions preventing the precipitation of long-chain surfactants, as commonly observed with alkali ions or unmodified choline. The resulting amphiphilic systems show superior properties with respect to surface activity, which directly translates into enhanced cleaning performance in lab-based washing tests. Studies on the cytotoxicity and biodegradability of the alkoxylated choline derivatives highlight their potential for sustainable surfactant development. In the end, our approach could pave the way towards the use of hitherto unleveraged raw material resources in tailoured surfactant formulations for cleaning applications and beyond. Choline alkoxylates were synthesised and used to solubilise long-chain surfactants under ambient conditions. In this way, so far underutilised natural feedstocks could be leveraged for the design of sustainable and efficient cleaning formulations.