Interactions between ethyl(hydroxyethyl) cellulose and lysine-based surfactants in aqueous media

In this work, the interaction between ethyl(hydroxyethyl) cellulose (EHEC) and three dimeric lysine-based surfactants of distinct chain length (C6, C8 and C10) have been assessed and the system was evaluated in terms of its temperature-dependent gelling capacity. The viscosity profile depends on the specific surfactant, its concentration and temperature. The observed profiles reflected polymer–polymer associations at elevated temperatures and polymer-surfactant interactions, implying the formation of micellar-type associations. The systems induce gelation at higher temperatures. Longer chain-length surfactants induce gelation at lower concentrations due to their stronger tendency to self-assemble. The thermo-responsive gels showed gel strength generally lower than 20 Pa.sn and a fractal dimension of 2.3–2.4, respectively, indicating the formation of soft gels comprising a tight and homogeneous network. The weakest gel was produced in the presence of the C6 surfactant. 2D Small-Angle Light Scattering patterns showed a pronounced effect of temperature in terms of the evolution of large hydrophobic clusters, an event precluded when high concentrations of the longer chain surfactants were used.

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► New polymer–surfactant systems forming hydrogels at elevated temperatures.
► Amino acid–based low toxicity surfactants.
► Promising systems for pharmaceutical formulations requiring in situ gelation.
► Longer chain-length surfactants induce gelation at lower concentrations due to their stronger tendency to self-assemble.