Stryutskii O. Synthesis, structure and properties of organic-inorganic proton-exchange membranes based on a,w-dialkoxysilane olygoether-containing precursors and sulfacidic protonodonors

The thesis is devoted to developing methods of synthesis of nanostructured organic-inorganic membranes with anhydrous proton conductivity using sol-gel method which is capable of operating at temperatures above 100oC and investigation of their structure and properties. A new approach to the synthesis of organic-inorganic proton-exchange membrane of this type, which is combining of protondonor compounds, capable of providing the single-ion mechanism of proton conductivity, with a,w-dialkoxysilane oligoether containig precursors that form oligoether proton conducting phase during sol-gel synthesis, is proposed. The main results were obtained with the use of modern methods of investigation: infrared spectroscopy, small-angle X-ray analysis, differential scanning calorimetry, atomic force microscopy, thermogravimetric analysis, dielectric relaxation spectroscopy. A number of new sulfonic protonodonors, including those capable of sol-gel transformations, with the urethane and urea fragments in their structure, which provide single-ion mechanism of proton transport in membranes based on them, is obtained. A new type of oligomeric dialkoxysilane precursors of the segmented structure that provide film-forming ability of the membranes and the formation of protonconducting oligoether phase is synthesized. A new type of oligomeric alkoxysilane protonodonors, which combine film-forming, protondonor, protonconducting properties with the ability to sol-gel transformations is proposed and obtained. On the basis of obtained protonodonors and oligomeric precursors the three types of organic-inorganic proton-exchange membranes, which differ in nature of attachment of protonodonor fragments to the organic-inorganic host, is synthesized. The synthesized membranes are characterized by the values of the static exchange capacity 0,31-1,65 meq/g, thermal stability of 220-325oC and the level of conductivity 10-6 - 10-4 S/cm at temperatures of 100-120 °C under anhydrous conditions. According to the obtained results the prototype of a fuel cell with a synthesized membrane is characterized by open-circuit voltage of 0,86 V. The proposed approach to the synthesis of proton-exchange membranes is used in obtaining of organic-inorganic lithium conducting polymer solid electrolytes that was used as effective active layers in the moisture sensors.