Isocyanates react with carboxylic acids and yield amides. What is reported herewith is that transferring that reaction to a range of mineral acids, (anhydrous H3BO3, H3PO4, H3PO3, H2SeO3, H6TeO6, H5IO6 and H3AuO3) yields urea. The model system for this study was a triisocyanate, tris(4-isocyanatophenyl)methane (TIPM), reacting with boric acid in DMF at room temperature yielding nanoporous polyurea networks that were dried with supercritical fluid CO2 to robust aerogels. Residual boron in the model system was quantified with prompt gamma neutron activation analysis (PGNNA). It was found very low (≤0.05 % w/w) and was shown to come primarily from B2O3 (by 11B NMR). Thus, any mechanism for systematic incorporation of boric acid in the polymeric chain, by analogy to carboxylic acids, was ruled out. Retrospectively, it was fortuitous that this work was conducted with aerogels, and the model system utilized H3BO3, whereas the byproduct, B2O3, could be removed easily from the porous network leaving behind pure polyurea. With other mineral acids results could have been misleading, because the corresponding oxides are insoluble and remain within the polymer (via skeletal density determinations and EDS). On the positive side, the latter is a convenient method for in situ doping robust porous polymeric networks with oxide or pure metal nanoparticles (Au in the case of H3AuO3) for possible applications in catalysis.

Nanoporous polyurea from triisocyanates reacting with mineral acids

251st National Meeting (2016)

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