Polymerization in nonaqueous lyotropic liquid crystals with a polymerizable solvent

Abstract

Lamellar liquid crystals of lecithin and 2-hydroxyethyl methacrylate (HEMA) were polymerized by using UV radiation. Optical microscopy, infrared spectroscopy, and small-angle X-ray diffraction were used to compare the structure prior to and after polymerization. The lamellar structure was retained after polymerization with increased interlayer spacing.

Photopolymerization in Polymer Templating

“…The use of LC templates can be further divided into a number of specific areas including (1) polymer/LC composites in which the templated polymer is used to structurally reinforce the LC or induce unique electro-optic properties, [31][32][33] (2) polymerizable LC mesogens that self-assemble and then are covalently locked into place, [34][35][36][37][38] or (3) the use of a nonreactive LC system as a structure-directing agent for a separate polymerization reaction, after which the LC is typically removed from the organic network. [39][40][41][42] As polymer templates grow in complexity, the preorganization of structure and subsequent polymerization in these systems result in a highly dynamic environment. For example, in LLC templating, a number of factors including thermodynamic interactions, solubility, reaction kinetics, functionality, and phase separation all directly contribute to the successful transfer of structure from the template to the growing polymer network.…”

“…While some papers report the direct replication of template structure within the formed organic polymer, others state that phase separation of the polymer from the template is the primary mechanism directing the architecture of the growing network and prevents a direct transfer of structure from the template to the polymer matrix. 12,28,[39][40][41]44,52 In fact, phase separation is one of the largest challenges in templating polymers within liquid crystal systems. Propagating polymer chains may directly influence the thermodynamic stability of the LLC/monomer formulations, resulting in phase separation and ultimately the destruction of the nanometer scale order of the LC system.…”

“…Liquid crystals are particularly well-suited for templating applications based on their ability to form different mesophases that possess highly ordered structural geometries ideal for directing polymerization reactions. , LCs used in polymer templating can typically be classified as either thermotropic liquid crystals (TLCs) or lyotropic liquid crystals (LLCs) in which the mesophase formation is determined primarily by temperature or concentration effects, respectively. The use of LC templates can be further divided into a number of specific areas including (1) polymer/LC composites in which the templated polymer is used to structurally reinforce the LC or induce unique electro-optic properties, – (2) polymerizable LC mesogens that self-assemble and then are covalently locked into place, – or (3) the use of a nonreactive LC system as a structure-directing agent for a separate polymerization reaction, after which the LC is typically removed from the organic network. – …”

“…Some of most successful template replications were discovered in the early 1990s in the synthesis of mesoporous silicate materials in the presence of surfactant templating structures. , This initial work has developed into a rapidly expanding field resulting in numerous papers and achievements in generating uniform, tunable mesoporous silicate materials with nanometer pore dimensionality. ,– Similar interest and extensive research have also focused on the generation of organic nanostructured polymers templated from LLC assemblies. While some papers report the direct replication of template structure within the formed organic polymer, others state that phase separation of the polymer from the template is the primary mechanism directing the architecture of the growing network and prevents a direct transfer of structure from the template to the polymer matrix. ,,– ,, In fact, phase separation is one of the largest challenges in templating polymers within liquid crystal systems. Propagating polymer chains may directly influence the thermodynamic stability of the LLC/monomer formulations, resulting in phase separation and ultimately the destruction of the nanometer scale order of the LC system.…”