Helical Polybissilsesquioxane Bundles Prepared Using a Self‐Templating Approach

Abstract

Polybissilsesquioxanes with single-handed helical morphologies attracted much attention during the last decade, which could be applied as asymmetric catalysts and chiral stationary phases. Herein, a pair of chiral biphenylene-bridged bissilsesquioxanes were synthesized. They self-assembled into helical bundles in ethanol, behavior that was confirmed in field emission scanning electron microscopy images. Circular dichroism analysis indicated that the biphenylene groups twisted in a single-handed fashion. Single-handed helical polybissilsesquioxane bundles were prepared via polycondensation of the bissilsesquioxanes, using a self-templating approach. Because of the shrinkage that occurred during polycondensation, the helical pitches of the bundles were shorter than those of their corresponding organic self-assemblies. The wide-angle X-ray diffraction pattern indicated that there were no π-π interactions among the diphenylene groups. The circular dichroism spectra indicated that the chirality was successfully transferred from the bissilsesquioxane self-assemblies to the polybissilsesquioxane. The polybissilsesquioxanes displayed a capacity for the adsorption of nitrobenzene and had potential application for enantioseparation.

Single-Handed Helical Polybissilsesquioxane Nanotubes and Mesoporous Nanofibers Prepared by an External Templating Approach Using Low-Molecular-Weight Gelators

“…If the biphenyl group twists in right-handedness, the CD signal at 278 nm is negative. The simulated CD spectrum is similar as the experimental one [44]. When the distance between neighbor biphenyl groups increases, the CD signals shift to short wavelength.…”

“…Nevertheless, it is difficult to control helical polysilsesquioxanes in enantiopure form, even after addition of chiral dopants [37,38,39]. To control the handedness, Moreau’s group performed pioneering research on sol–gel transcription using LMWGs as self-templates [40,41,42,43,44]. Here, we discuss polybissilsesquioxanes with helical morphologies prepared by an external approach using LMWGs [45,46,47,48,49,50,51,52,53,54,55,56,57,58,59].…”

The Role of Chirality and Helicity between d- and l-Valine Optical Lattices

“…In summary, chirality and helicity in nature has intrigued chemists and physicists for a century [17][18][19]. The significance of this article provides evidence for the role of chirality and helicity life.…”

Chiral Nanoceramics

“…Most of organic amphiphiles can be assembled into chiral superstructures. [ 43 ] This series of superstructures can be used as soft templates in the preparation of helical ceramic nanomaterials including, SiO 2 , [ 44 ] Ta 2 O 5 , [ 45 ] TiO 2 , [ 46 ] ZrO 2 , [ 47 ] and poly(bissilsesquioxane) [ 48 ] via the sol–gel transcription approach. Similarly, bio‐macromolecules, such as peptides and DNA can serve as templates for realizing chiral ZnO [ 49 ] and silica structures.…”