A new family of polymerizable lyotropic liquid crystals: Control of feature size in cross-linked inverted hexagonal assemblies via monomer structure

An efficient and versatile synthesis of a series of polymerizable amphiphil ic mesogens that affords control over tail length and position of the :poly merizable group is described. The synthesis employs a novel and facile meth od of preparing styrene ethers. The monomers are sadium salts of styrene et her-modified fatty acids that can be used to form cross-linkable inverted h exagonal (H-II) lyotropic liquid crystal (LLC) phases at ambient temperatur e with controllable nanometer-scale dimensions. Examination of a series of regioisomers with the same alkyl chain length but with the styrene: ether g roup at different locations along the chain revealed that the position of t he 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 c ell dimensions of the LLC phase. By controlling the structure of the LLC mo nomer in this manner, cross-linked HII phases with interchannel distances ( ICD) ranging from 29 to 54 Angstrom can be obtained. Furthermore, changing the counterion from Na+ to tetraalkylammonium ions leads to further expansi on of the H-II unit cell to a maximum ICD of 65 Angstrom, as well as to the production of a lamellar phase. Use of these monomers affords a new and un paralleled degree of control over phase structure and dimensions for the pr oduction of nanostructured organic materials.