Thermoresponsive liquid crystalline polymer membranes that undergo phase transition at body temperature

Biological membranes regulate their properties and functions by drastic changes in their organized structure and mobility in response to changes in environmental factors such as pH, temperature, and biomolecule concentration. Liquid crystalline polymers (LCPs) are widely used as functional materials in a variety of fields because, similarly to biological membranes, they undergo abrupt changes in their organized structures and mobilities at their phase transition temperatures. In order to design smart membranes that regulate drug permeability as a function of temperature, we focused on well-organized and dynamic LCPs that undergo liquid crystalline-isotropic phase transition around body temperature. In this study, side-chain LCPs composed of a flexible siloxane main chain and pendant mesogens were synthesized and LCP membranes were prepared by casting the LCPs/xylene on porous support membranes. The nematic-isotropic phase transition temperature (TNI) of the resulting LCPs strongly depended on the mesogen content. Although the permeation of drugs through the LCP membranes was hindered at temperatures below TNI, their drug permeability was drastically enhanced over TNI. Thermoresponsive regulation of drug permeation through the LCP membranes is attributed to the drastic changes in their well-organized and dynamic structures that are induced by the nematic-isotropic phase transition.