Mesostructured Polymer and Glass Microfiber Nonwovens with Supramolecular 1,3,5-Benzenetrisamide Nanofibers for Air Filtration.

Hierarchically mesostructured nonwovens with complex fiber morphologies are gaining more and more interest for filtration applications as the increased surface area offers improved filtration efficiencies for particulate matter. Several concepts are known to fabricate such complex fiber morphologies; however, the control over the morphology remains challenging. Here, we report on the preparation of mesostructured nonwovens decorated with defined supramolecular nanofibers by physical vapor deposition of a selected commercially available 1,3,5-benzenetrisamide (BTA). Using polymer nonwovens as a support, we show that with this solvent-free process, the supramolecular nanofiber length can be tuned from 5 to 20 μm depending on the evaporation time resembling a bottlebrush-like morphology on the mesoscale. Whereas the model polymer nonwoven is unsuitable to capture particulate matter, the mesostructured nonwovens show an increasingly improved filtration efficiency of up to 87% for 2.0 μm particles at a low pressure drop of 90 Pa. Since the selected BTA has a pronounced thermal stability, this also enables the preparation of more temperature-resistant mesostructured nonwovens using a glass microfiber nonwoven as a support. We show that the morphology as well as the filtration efficiency of the mesostructured glass fiber nonwoven is maintained even after heat treatment at 200 °C for 24 h. This cannot be realized with nonwovens based on commodity polymers and engineering plastics. These results prove the general applicability of vapor-deposited supramolecular nanofibers and broaden the application window for such mesostructured nonwovens in the field of filtration and separation toward more efficient, robust, and also selective filter media.