Polymerizable Lyotropic Liquid Crystals Containing Transition-Metal and Lanthanide Ions: Architectural Control and Introduction of New Properties into Nanostructured Polymers

Abstract

The development of synthetic materials with controlled nanostructures is currently an active area of materials research.1 Recently, our group devised a new method for synthesizing polymer-based nanocomposites which involves the cross-linking of lyotropic (i.e., amphiphilic) liquid crystals (LLCs)2 that adopt the inverted hexagonal phase (Scheme 1).3,4 Inorganic3 and organic polymer chemistry4 can be performed inside the hydrophilic domains of these ordered assemblies, and the nanocomposites can be processed into films and fibers prior to photopolymerization.4 The materials formed inside the periodic microdomains exhibit different properties than corresponding materials formed in bulk or in solution. The constrained environment apparently limits the degree of conversion of these materials, imparting them with different structures than those obtained in bulk.3,4 Because of this apparent effect of reaction environment size in these systems, we sought to develop methods for varying the small-scale dimensions of these nanocomposites. The geometry of LLC phases depends greatly upon the shape of the amphiphile.5 Amphiphiles with a small hydrophilic headgroup and a broad, wedge-like hydrophobic tail section would tend to assemble into the inverted hexagonal phase, based on straightforward packing considerations.6 Because of the ionic nature of our monomers, the use of different metal cations might serve as a viable means of (1) modulating headgroup size and consequently the internal dimensions of the hexagonal assemblies and (2) introducing new properties into these systems.