A New Family of Polymerizable Lyotropic Liquid Crystals:  Control of Feature Size in Cross-Linked Inverted Hexagonal Assemblies via Monomer Structure

Abstract

An efficient and versatile synthesis of a series of polymerizable amphiphilic mesogens that affords control over tail length and position of the polymerizable group is described. The synthesis employs a novel and facile method of preparing styrene ethers. The monomers are sodium salts of styrene ether-modified fatty acids that can be used to form cross-linkable inverted hexagonal (H II ) lyotropic liquid crystal (LLC) phases at ambient temperature with controllable nanometer-scale dimensions. Examination of a series of regioisomers with the same alkyl chain length but with the styrene ether group at different locations along the chain revealed that the position of the styrene ether has a profound effect on the dimensions of the resulting H II phase at a fixed temperature and composition. Increasing overall monomer tail length also has a significant, although smaller, effect on the unit cell dimensions of the LLC phase. By controlling the structure of the LLC monomer in this manner, cross-linked H II phases with interchannel distances (ICD) ranging from 29 to 54 Å can be obtained. Furthermore, changing the counterion from Na + to tetraalkylammonium ions leads to further expansion of the H II unit cell to a maximum ICD of 65 Å, as well as to the production of a lamellar phase. Use of these monomers affords a new and unparalleled degree of control over phase structure and dimensions for the production of nanostructured organic materials.