Phosphazene polymers are unique in their ability to be chemically altered to provide a variety of chemical and physical properties, which has attracted their use as membranes for gas separation processes. Post-polymerization functionalization allows polymers to be designed with multiple pendant groups in varying amounts, allowing the properties of the polymer to be tuned by the nature of the functional groups coordinated to the backbone. This relatively simple synthetic approach is particularly appealing for the development of materials used in industrial processes, such as the capture of CO2 from flue gas. Our lab has prepared a variety of polyphosphazenes with systematic alterations in their formulations, and studied their chemical and physical properties as potential gas separating materials. It has been observed that the incorporation of pendant group, 2-(2-methoxyethoxy) ethanol (MEE), provides favorable CO2 permeability and selectivity over other gases, and a strong correlation between these gas separation properties and MEE functionality has been observed. However, MEE substitution results in a soft/sticky polymer not amenable to the production of stable membranes. Research efforts from our lab have been focused on the stabilization of MEE-based membranes without greatly reducing permeability and selectivity. A variety of strategies have been tested, including using a limited amount of additional pendant groups to add mechanical stability to the polymer, as well as forming interpenetrating networks with multiple polymers. In addition, membranes have been stabilized by incorporating an internal support structure through the use of inorganic additives. Recently, crosslinking has been used to add stability to MEE-based membranes while maintaining good gas separation performance. A broad overview of our research efforts related to the stability of MEE-based polyphosphazene membranes, for gas separation processes, will be presented.

Mechanical stabilization of polyphosphazene membranes for gas separation processes

254th National Meeting (2017)

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