Grafting polymerization of single‐handed helical poly(phenyl isocyanide)s on graphene oxide and their application in enantioselective separation

Abstract

We herein report a "grafting from" strategy to immobilize optically active helical poly(phenyl isocyanide)s onto graphene oxide (GO) nanosheets. After covalently bounding alkyne-Pd(II) initiator onto GO nanosheets, the designed GO/polymer composites P1@GO and P1-b-P2@GO featuring single-handed helical poly(phenyl isocyanide)s growing from GO nanosheets were prepared by sequential addition of the chiral and achiral isocyanide monomers. Post-synthetic hydrolysis rendered P1-b-P3@GO to improve the hydrophilicity. The successful covalent bonding of poly(phenyl isocyanide)s chains onto GO nanosheets was certified by several cross evidences including scan emission microscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Circular dichroism spectra proved that the chiral information was introduced through the grafted single-handed helical polymer chains successfully. In addition, the resulting GO/polymer composites were explored as a chiral additive to induce enantioselective crystallization of racemic organic molecules. Preferential formation of rod-like L-alanine crystals was induced by composites bearing right-handed helical poly(phenyl isocyanide)s. The enantiomeric excess value of the induced crystals reached 76%, displaying the potential in future applications.

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

“…Zhu and co‐workers reported a “grafting from” strategy for immobilizing chiral helical poly(phenyl isocyanide)s onto GO nanosheets. [ 171 ] Multiple characterizations confirmed the success in grafting chiral polymer on the substrate. Chiral helical polymer chains afford GO with optical activity.…”

“…Apart from chiral helical polyacetylenes, Zhu and co‐workers prepared chiral hybrid materials using GO and chiral helical polyisocyanides. [ 171 ] Just like chiral helical polyacetylenes discussed above, the formation of hybrids with GO layers cannot prevent the polyisocyanide chains from forming chiral helical structures. The helical polymer endowed the hybrid materials with intriguing optical activity.…”

A One‐Pot Polymerization for Concurrently Inducing Predominant Helicity in Optically Inactive Helical Polymer and Constructing Graphene‐Based Chiral Hybrid Foams

“…Nonetheless, there have been a lot of reports dealing with integrating graphene foams with polymers. Chiral helical polymers are rarely used to functionalize graphene …”

β‐Cyclodextrin Functionalized Nanoporous Graphene Oxides for Efficient Resolution of Asparagine Enantiomers

“…In this way, chiral GO enantioselective sensors were demonstrated . However, this general recognition phenomenon has been rarely applied to separate enantiomers or racemates because of great challenges in fabricating chiral GOs with efficient enantioselective resolution capabilities . This low efficiency is probably due to insufficient chiral host molecules and mismatch between chiral host and guest pairs .…”

“…[13] However,t his general recognition phenomenon has been rarely appliedt os eparate enantiomers or racemates because of great challenges in fabricating chiral GOs with efficient enantioselective resolution capabilities. [14] This low efficiency is probably due to insufficient chiral host molecules and mismatch between chiral hosta nd guest pairs. [15] Moreover, insteado fi nvestigatingt he "response/ signal" difference between pure d-a nd l-enantiomers in these chiral sensors, separating one enantiomer from am ixture of racemic enantiomersi so fp articulard ifficult because of fierce competition between the two enantiomers.…”