Synthesis, Characterization And Emission Properties Of A Supramokecular Cross-linked Polymeric Network Controlled By Acid-Base Reaction

Supramolecular polymers, which are fabricated by intermolecular noncovalent interactions, not only show traditional polymeric properties, but also possess new structures and functions, leading to potential applications as supramolecular materials. A variety of noconvalent interactions, including multiple hydrogen bonding,π-π stacking, metal-ligand coordination, and intergrated noncovalent interactions, have been used to fabricate supramolecular polymers. With the development of supramolecular polymers, more sophisticated supramolecular polymeric materials are in demand to solve problems currently encountered in the field of life science and functionalized materials. Therefore, supramolecular cross-linked polymeric networks are widely studied, which hold potential applications in drug delivery, chemical sensor, shape-memory materials and etc. However, rare example was demonstrated using polymers simultaneously grafted with host and guest groups. Here, we report the fabrication of a supramolecular cross-linked polymeric network through a π-conjugated polymer simultaneously bearing dibenzo[24]crown-8 (DB24C8) and dibenzylamine groups.Firstly, a π-conjugated AB monomer 2 with DB24C8 and dibenzylamine group has been synthesized and used to fabricate a linear supramolecular polymer for guiding the more complex supramolecular polymeric network.A π-conjugated polymer 1 simultaneously bearing DB24C8 and dibenzylamine groups has then been synthesized and used to fabricate a supramolecular cross-linked polymeric network. Upon treatment the solution of polymer 1 with hexafluorophosphoric acid (HFA), the protonated dibenzylamine group results in dibenzylammonium (DBA) center, which is then threaded by DB24C8 through [N+—H···O] and [C-H···O] hydrogen bonds and π-π stacking interactions. The host-guest interactions induce the formation of supramolecular cross-linked polymeric network HFA-1.This polymeric network can been completely decross-linked by N-tert-butyl-N’N’N",N"N,’",N’"-hexamethylphosphorimidic triamide. The reversible HFA-1 also shows a significant change in their fluorescence intensities, which hold a potential application as smart materials.