Solid state nanofibers based on self-assemblies: from cleaving from self-assemblies to multilevel hierarchical constructs.

Self-assemblies and their hierarchies are useful to construct soft materials with structures at different length scales and to tune the materials properties for various functions. Here we address routes for solid nanofibers based on different forms of self-assemblies. On the other hand, we discuss rational "bottom-up" routes for multi-level hierarchical self-assembled constructs, with the aim of learning more about design principles for competing interactions and packing frustrations. Here we use the triblock copolypeptide poly(L-lysine)-b-poly(gamma-benzyl-L-glutamate)-b-poly(L-lysine) complexed with 2'-deoxyguanosine 5'-monophosphate. Supramolecular disks (G-quartets) stabilized by metal cations are formed and their columnar assembly leads to a packing frustration with the cylindrical packing of helical poly(gamma-benzyl-L-glutamate), which we suggest is important in controlling the lateral dimensions of the nanofibers. We foresee routes for functionalities by selecting different metal cations within the G-quartets. On the other hand, we discuss nanofibers that are cleaved from bulk self-assemblies in a "top-down" manner. After a short introduction based on cleaving nanofibers from diblock copolymeric self-assemblies, we focus on native cellulose nanofibers, as cleaved from plant cell wall fibers, which are expected to have feasible mechanical properties and to be templates for functional nanomaterials. Long nanofibers with 5-20 nm lateral dimensions can be cleaved within an aqueous medium to allow hydrogels and water can be removed to allow highly porous, lightweight, and flexible aerogels. We further describe inorganic/ organic hybrids as prepared by chemical vapour deposition and atomic layer deposition of the different nanofibers. We foresee functional materials by selecting inorganic coatings. Finally we briefly discuss how the organic template can be removed e.g., by thermal treatments to allow completely inorganic hollow nanofibrillar structures.