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Nanofibers Made By Self-assembly

2019-05-23


           
Nanofibers Made By Self-assembly

Cellulose nanofibrils are produced by the bacteria Acetobacter xylinum in a complex bottom-up process. Self-assembly of small molecules at the molecular level (supramolecular chemistry) is the bottom-up method of making nano- and mesostructures. The self-assembly toward various aggregate morphologies can be controlled by external conditions such as temperature, solvent, and concentration to tailor them. Molecular self-assembly organizes molecules into a thermodynamically stable structure under equilibrium conditions. The fibers produced by this method can be as thin as <10 nm but mostly limited in length (also called nanotubes, nanorods, and nanowires). Noncovalent interactions, such as van der Waals forces, H-bonding, ionic interactions, hydrophobic interactions, pep stacking, and metal coordination, are responsible for self-assembly. One of the supramolecular motifs capable of forming nanofibers comprises 1,3,5-benzenetrisamides (BTAs) (Cantekin et al., 2012). Mostly, BTAs form columnar stacks during self-assembly processes driven by three directed self-complementary hydrogen bonds and pep stacking (of the benzene units) into one-dimensional (1D) primary aggregates. The generated fibers have high aspect ratio (500:1). The amide connectivity and the type of alkyl substituents mainly influence the diameter of the fibers and their morphology, but have a minor influence on their modulus (Kluge et al., 2012). The morphology and diameter of fibers made by the self-assembly of three different BTAs (Scheme 4.1) is shown in Fig. 4.3.

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