Thermoresponsive Membranes from Lyotropic Liquid Crystal Templates

We study the fabrication of thermoresponsive membranes from the polymerization of lyotropic liquid crystals (LLCs) composed of poloxamers, diacrylated Poloxamers, oil, and water in this experimental work. After formation of Lyotropic Liquid Crystals, the oil phase (containing monomers) and Poloxamer can be crosslinked to make mechanically robust membranes with pore sizes in the range of 1-10 nm, thereby conducting nanofiltration/ultrafiltration of samples. The overall purpose of this study is leveraging the stimulus-responsive behavior of the membranes since they show great potential in a variety of fields, such as pharmaceuticals, oil processing, protein purification and chemical detection. Poloxamers are non-toxic, amphiphilic (hydrophilic head and hydrophobic tail), non-ionic surfactants and their structure consists of poly(propylene oxide) which are hydrophobic and poly(ethylene oxide) blocks which are hydrophilic. Lyotropic liquid crystals are a result of the self-assembly of these amphiphilic molecules, water, and oil in a ternary system, where depending on the composition, different crystal structures, such as lamellar, cubic, and hexagonal phases, are produced. The study finds that, as shown by significant liquid crystalline transitions, a 50/50 mixture of diacrylated and pristine Poloxamers is the most effective ratio for creating thermoresponsive membranes with a normal hexagonal (H1) lyotropic liquid crystal structure. Additionally, the combination of diacrylated and pristine Poloxamers improves the structural stability of the mesophase of the lyotropic liquid crystal, resulting in a thicker gel whose viscosity decreases at lower temperatures and increases at higher temperatures. The change in viscosity based on temperature demonstrates the thermal responsive behavior of the membranes. When testing permeability of the membranes, a water flux of 34.25 L/m^2.h is calculated and molecular weight cut off test are completed to observe rejection capabilities of the membranes. The potential of the LLC templating method in creating customized thermoresponsive membranes, which are reproducible for protein separation applications is highlighted by this study.