Polymer Gels with a Micron-Sized, Layer-like Architecture by Polymerization in Lyotropic Cocogem Phases

Abstract

Polymerization of hydrophilic monomers, such as acrylamide, in the aqueous lyotropic phases of counterion-coupled gemini surfactants (“cocogems”) results in highly ordered gels with a layerlike architecture between the submicrometer and micrometer length scale. The order of such gels is preserved even after removing the templating surfactant. The evolution of the gels is monitored using polarized light optical microscopy, rheology, small-angle X-ray scattering, and scanning electron microscopy (SEM). The synthesis envokes structural changes of the templating lyotropic phase structure as well as demixing of the gelling polymer and the surfactant phase. The overall gel morphology is, however, still controlled by the anisotropy of the surfactant assembly. Hence, the polymer gel is not a direct cast of the original phase structure, but its growth is indirectly controlled by the ordered arrays. The persistence of the lyotropic liquid crystalline phases of cocogems is high enough to preserve a layered order, however with the characteristic size of a demixing structure rather than that of the parental lyotropic phase. Chemical functionalization of these gels is easily achieved by copolymerizing functional comonomers, such as acrylic acid or dimethylaminoethyl methacrylate. It is expected that these ordered gels, simple to prepare and inexpensive, will find a number of applications in various fields of modern materials science, such as for the construction of size-selective membranes or high-performance material hybrides.