Minimal hydration of small molecule surfactants drives their cooperative and non-covalent self-assembly by virtue of the hydrophobic effect, leading to the formation of lyotropic liquid crystals (LLCs) with periodic nanoscale structures.  Characterized by highly tortuous, interpenetrating networks of hydrophobic and hydrophilic channels, bicontinuous LLCs are particularly useful in myriad applications. As a consequence of their non-constant mean curvatures, these bicontinuous LLCs are somewhat difficult to access using traditional single-tail surfactants. Motivated by recent experimental reports that suggest that gemini amphiphiles favor the formation of bicontinuous LLCs, we have studied the synthesis and self-assembly behavior of bis(alkyltriazolium) gemini surfactants bearing I-, Cl-, and NO3- counterions using a combination of optical birefringence and small-angle X-ray scattering. We have found that the hydrophilicity of the counterion controls the size of the composition windows over which LLC phases form. We further show that bis(alkyltriazolium) gemini surfactants furnish access to two non-constant mean curvature LLCs: (1) the inverse gyroid phase, and (2) an unprecedented inverse phase with Pm3(-)n symmetry, comprising tetrahedrally-closest packed micelles. We rationalize our observations in terms of a model, whereby a combination of intra- and inter-molecular electrostatic interactions specified by the surfactant structure and counterion-headgroup hydration guide the formation of these technologically useful phases.

Impact of molecular architecture on lyotropic liquid crystals derived from bis(alkyltriazolium) gemini amphiphiles

248th National Meeting (2014)

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