Abstract
Chiral and helical polymers possess special helical structures and optical property, and may find applications in chiral catalysis and optical devices. This work presents the preparation and formation process of helical phenolic resins through a sol-gel transcription method. A pair of bola-type chiral low-molecular-weight gelators (LMWGs) derived from valine are used as templates, while 2,4-dihydroxybenzoic acid and formaldehyde are used as precursors. The electron microscopy images show that the phenolic resins are single-handed helical bundles comprised of helical ultrafine nanofibers. The diffused reflection circular dichroism spectra indicate that the helical phenolic resins exhibit optical activity. A possible formation mechanism is proposed, which shows the co-assembly of the LMWGs and the precursors.
Highlights
Chiral and helical structures can often be found in nature, for instance, α-helical polypeptides, double helical nucleic acids, spirulina and spiral shells
These chiral low-molecular-weight gelators (LMWGs) can self-organize into a variety of chiral nanostructures such as coiled ribbons, twisted nanofibers and bundles [8], and lots of chiral and helical, inorganic or organic materials, such as silica and polysilsesquioxane nanotubes, nanoribbons and nanofibers have been successfully synthesized from these templates [9,10,11,12]
In recent years, ordered mesoporous phenolic resins have attracted much attention because they can act as a promising carbon source to fabricate ordered mesoporous carbons [13,14,15]
Summary
Chiral and helical structures can often be found in nature, for instance, α-helical polypeptides, double helical nucleic acids, spirulina and spiral shells. Remarkable progress has been achieved by a sol-gel transcription method using the self-assemblies of chiral low-molecular-weight gelators (LMWGs) as templates [4,5,6,7]. These chiral LMWGs can self-organize into a variety of chiral nanostructures such as coiled ribbons, twisted nanofibers and bundles [8], and lots of chiral and helical, inorganic or organic materials, such as silica and polysilsesquioxane nanotubes, nanoribbons and nanofibers have been successfully synthesized from these templates [9,10,11,12]. The co-assembly of the chiral templates and the phenolic resin precursors determined the chiral structure and optical activity of the nanotubes. FE-SEM images images of of the the reaction reaction mixture mixture taken formation during the reaction
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