Methods of adjusting the properties of a composition are provided. The compositions comprise a polymer-containing matrix and a filler comprising a hygroscopic salt. Preferred such salts comprise a cage compound selected from the group consisting of borane cage compounds, carborane cage compounds, metal complexes thereof, residues thereof, mixtures thereof, and/or agglomerations thereof, where the cage compound is not covalently bound to the matrix polymer.
The present invention was developed with support from the U.S. government under a contract with the United States Department of Energy, Contract No. DE-NA-0000622. Accordingly, the U.S. government has certain rights in the present invention.