Pillararene-based Fluorescent Cross-linked Supramolecular Polymer Constructed By Host-guest Interactions

Supramolecular polymer is a new kind of smart material and has been a hot research topic these years. It is the aggregate of monomers assembled by non-covalent interactions, and has the advantages of both supramolecular and polymers. Due to the reversibility of non-covalent, the polymerization and its inverse process can be observed easily, which can give the supramolecular polymers excellent mechanical properties, recyclability, self-healing and responsibility to stimuli that the conventional polymers do not have. The main research about host-guest interactions focuses on the recognition and assembly of the macrocyclic host and guest molecular, and because of its unique advantages, the host-guest interactions have been one of the most important methods to construct supramolecular polymers. As a new generation of macrocyclic host, pillararene possesses a wide range of excellent properties that other macrocyclic hosts like crown ether, calixarene do not have and become one of the hot research topics in recent years. According to the topology, in the area of the pillararene-based supramolecular polymers constructed by host-guest interactions, there are many reports about linear supramolecular polymers, in constast, the study about cross-linked supramolecular polymers is not sufficient, especially the cross-linked supramolecular polymers that have fluorescence. Therefore, we designed the pillararene-based fluorescent cross-linked supramolecular polymer constructed by host-guest interactions, and the specific results are as followed:1. Build the cross-linked supramolecular polymers which have stimuli responsive properties by host-guest interactions. We designed and synthesized a novel self-complementary AABB-type heteromultitopic monomer (APOPV). It is composed of the rigid oligo(p-phenylenevinylene) (OPV) dye as a bridge, two pillar[5]arenes at the terminal as hosts and two n-dodecyl chains perpendicular to the OPV backbone as guests. Therefore, a new fluorescent cross-linked supramolecular polymer can be constructed solely from APOPV, held together by host-guest interactions of pillar[5]arenes with alkyl chains. It is confirmed that there are host-guest interactions and the ?-? interactions do not exist in this system by 1H NMR and UV-Vis spectra. The DOSY spectrum, dynamic light scattering (DLS) and SEM can explain that the APOPV can construct cross-linked supramolecular polymer in high concentration, and the gel can be observed when the concentration is more than 69 mM. the APOPV gel not only has stimuli-responsive performance to temperature, but also can respond to the acid-base stimuli. When the gel is coated into a film, the fluorescence of the APOPV film was quenched immediately when exposed to TFA vapor, and recovered completely after exposure to TEA vapor. This result suggested a potential application of the APOPV-based cross-linked supramolecular polymers as an acidic sensor.2. Build the cross-linked supramolecular polymer that has FRET property. We designed and synthesized a molecular that with oligo(p-phenylenevinylene) (OPV) dye to bridge two pillararenes (PA-OPV) as host, a molecular that with porphyrin to bridge four cyano groups (CN-Por) as guest, and they can construct cross-linked supramolecular polymer by host-guest interactions. It can be confirmed the formation of cross-linked supramolecular polymer through 1H NMR, NOESY spectrum, DOSY spectrum, specific viscosity, SEM. The fluorescence resonance energy transfer (FRET) phenomenon can be observed in this cross-linked supramolecular polymer by the results of fluorescence spectra and fluorescence lifetime, the emission of PA-OPV can excite CN-Por and emit its fluorescence. Therefore this cross-linked supramolecular polymer has potential application in light capture systems, optical switching devices and biological probes, etc.