Chiroptical Cross‐Linked Polymers Grown via Radical Polymerization around Chiral Nanosilica

Abstract

known whether organic matter or inorganic matter first brought chiral sources to our planet. In the field of chiral materials, chirality transfer system between organics and inorganics deserve to be a vitally important area to bring meaningful hints to not only the origins of life but also the development of chiral materials. The concept in this article is a radical synthesis of chiral polymers from achiral monomers employing a chiral inorganic silica as a chiral reaction matrix where chiral information could be transferred from silica to polymers.Chiral polymers have received much attention due to its unique stereochemistry and functionality, and many efforts have been devoted to the extension of their synthetic ways and applications. [12][13][14] One of general ways for the synthesis of chiral polymers involves the polymerization of optically active monomers. [15][16][17][18] However, this is not convenient due to the tedious synthesis of optically active monomers. The asymmetric polymerization, which directly produced chiral polymers starting from prochiral (achiral) monomers, is much more fascinating, and has been widely employed to design a variety of chiral polymers for the last several decades. There are some effective ways to synthesize chiral polymers that began from achiral monomers in conjunction with chiral reagents or catalysts. For instance, helix-sense-selective polymerization can afford chiral polymers with stable helical conformations via polymerization of achiral monomers having a large steric hindrance, in which the direction of the helicity could be entirely controlled by chiral catalysts, [19][20][21] initiators, [22,23] solvents, [24][25][26] and additives. [27][28][29] Besides that, chiral molecular imprinting is the simple technique of creating chiral recognition holes inside polymeric matrixes, which are complementary to the template of chiral molecules. [30][31][32] Other than the use of molecular-level assistances as chiral sources, the utilization of chiral nematic phase as a polymerization solvent is thought to be one of the effective methods to endow the helical organization on the resulting conjugated polymers. [33][34][35] Indeed, the asymmetric synthesis of chiral polymers has been remarkably advanced with the development of chiral reagents or catalysts, which play an essential role in the control of asymmetric configurations or conformations of the resulting polymer chains. However, the chirality of polymer-specific agents or catalysts has been ruled by organic molecular systems. To the best of our knowledge, there are no examples of using inorganic chiral materials as Chiral polymers are often prepared by two ways depending upon chiral monomers, chiral catalysts, and chiral auxiliaries which always come from organics: one is the enantio-selective polymerization of prochiral or racemic monomers or polymerization of optically active monomers; and the other one is the molecular imprinting technique, which creates chiral recognition sites inside a densely cross-linked polymer gel. H...

Fascinating chiral information transfer to titania/silica from near to racemic compound self-organized from polyethyleneimine and tartaric acid

“…49 They are formed by the similar covalent bond of Si-O and Ti-O, respectively, with a tetraoxycoordinated structure. Although we have succeeded in employing the chiral crystalline complex of PEI/Tart for the construction of chiroptical minerals of silica and titania, as well as their application in developing chiroptical materials, [50][51][52][53][54][55][56][57][58][59] the relationship between the component of the catalytic templates and the chiroptical activity of the silica/titania are still not well understood.…”

A versatile messenger for chirality communication: asymmetric silica framework

“…In a recent study, the powders of PEI/tart@SiO 2 were firstly treated under high temperature (600 °C) in air to remove the organic species of PEI and tart. As shown in Figure 6A, four types of silane coupling agents (SCAs) were selected, namely, 3-(trimethoxysilyl)propylamine (with a primary amino group of NH 2 -, 1°P), N-methyl-3-(trimethoxysilyl)propylamine (secondary NHMe-, 2°P), N,N-dimethyl-3-(trimethoxysilyl)propylamine (tertiary NMe 2 -, 3°P) and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole (with an imidazole group, Im) [47] . These SCAs were used as surface modifiers to prepare amine-modified chiral SiO 2 (i.e., 1°P-SiO 2 , 2°P-SiO 2 , 3°P-SiO 2 and Im-SiO 2 ).…”

“…(E) A proposed polycondensation reaction of R with F on the chiral SiO 2 surface chemically bonded with amine residues. This figure is used with permission from the Royal Society of Chemistry [47] . SCA: Silane coupling agent; CD: circular dichroism; R: resorcinol; F: formaldehyde.…”