Self-Assemble Of Amphiphilic Polyether Based Liquid Crystalline Block Copolymers

Two series of well-defined polyether backbone based amphiphilic liquid crystalline(LC)-coil block copolymers containing pendent hydrophobic LC mesogens and hydrophilic ethylene oxide(EO)oligomer side groups have been successfully synthesized by using anionic ring-opening polymerization(AROP).We have investigated the effects of LC ordering on the self-assembly of these block copolymers in bulk and solution.The phase behavior and structures of the polyether based liquid crystalline block copolymer have been studied by combining various techniques including differential scanning calorimetry(DSC)and small angle X-ray scattering(SAXS).Only one phase transformation is generally observed for each type of block copolymers.Different self-assembled structures were found in these copolymers and the phase diagram has been constructed.The structure and morphology of the amphiphilic block copolymers in dioxane/water co-solvent have been investigated in details,which should be driven mainly by the incompatibility between these two types of side groups,with negligible influence from the flexible main chain.We found that the morphology of these amphiphilic block copolymers could be tuned systematically by varying the water content.With increasing the water concentration above a critical value,the morphologies of the block copolymers were found to transform from spheres to vesicles and finally to faceted vesicles consistently.The observation of the faceted vesicle has been attributed to the formation of LC ordered structure as proved by 2D wide-angle X-ray diffraction.The delicate balance of the collective LC interactions and free energy of core,corona and interface dictates this unique behavior.The formation of the vesicles on the 100 nm scale could be potentially useful in biotechnological applications.