PNNL

Abstract

In biological environment, mineral crystals exquisitely controlled by biomacromolecules often show intricate hierarchical structures and superior mechanical properties. Among these biominerals, spicules, hybrid silica/protein superstructures serving as skeletal elements in demosponges, represent an excellent paradigm for the bottom-up construction of predictive hybrid silica materials. Herein, we report the design of sequence-defined peptoids that self-assemble into nanofibers, and further demonstrate their ability to template the formation of silica fibers at near-neutral pH and ambient temperatures. While the peptoids with the same hydrophobic domain but variable hydrophilic side chains form similar nanofibers, the variation of hydrophilic side chains has a significant impact on peptoid fiber formation and further silicification. While nanofibers assembled from peptoids containing six amino side chains are highly efficient for silicification, the yield of such nanofibers at near-neutral pH is quite slow. By arranging amino and carboxyl groups alternately in the hydrophilic domain, we demonstrated both high yield peptoid nanofiber formation and efficient silicification to form silica nanofibers. However, neither catalytic activity nor templating ability for silicification could be observed for peptoid nanofibers without amino groups, highlighting the importance of amino groups in silicification. Since peptoids are highly robust and programmable and the self-assembly of peptoids into hierarchical materials are highly controllable, we expect that this research opens new opportunities in the synthesis of organic-inorganic hybrid materials. Peptoid nanofibers with tunable surface chemistries offer great potential as catalytic templates for other technologically relevant inorganic materials, such as various metal oxide and carbonate materials.