The RAFT Reaction Is Used To Realize The Hierarchical Self-assembly Study Of Small Molecules

Supramolecular entities play an important role in molecular devices,sensors,medical sustained-release,cell recognition.However,it is too narrow that the choice scopes of monomeric unit,including triphenylene,phthalocyanine,porphyrin,and helicene,which are characterized by large aromatic cycles.The main driving force of supramolecualr polymerization derives from?-?interaction and solvophobic effects.Some small molecules with excellent biological properties but lack of strong ability in self-assembly often fail to self-assemble into supramolecular entities spontaneously.In this paper,the association of small molecules with excellent biological properties and low-entropy chains was fulfilled by RAFT fashion.The polymerization of some monomers such as vinyl acetate,N-vinyl-pyrrolidone,N-isopropylacrylamide were mediated by syntheses chain transfer agents(CTA)in advance such as O-Ethyl S-(Phthalimidylmethyl)Xanthate,S,S-1,2-phenylene-bis(methylene)-0,0-diethyl ester etc.A series of low-entropy chains tethered small molecules such as B-PVAc?B-PVA?PT-PVAc?PT-PVA?PT-PVP?PT-PNIPAM were prepared.The certification of resulting polymers and determination of molecular weight were performed by H¹NMR?C¹³NMR and GPC respectively.The morphologies of supramolecular entities were characterized by FE-SEM,TEM and AFM,determining the size of them with DLS.Meanwhile,fluorescent properties,fluorescence life-time,fluorescent anisotropy were determined by UV-Vis,FL,Transient FL,LCSM respectively.The resulting PT-PVAc can form vesicles spontaneously in good solvent THF andDMSO,manifesting obvious concentration-dependent and aged-time dependent hierarchal self-assembly from vesicle to nano-tubes,gels.Meanwhile,the terminal small molecules transformed from free monomeric state to J-type state,accompanied with the fluorescence of benzene red-shifted from 350 nm to 410 nm and that of phthalimides red-shifted from 430 nm to 530 nm.In addition,the resulting PT-PVA?PT-PVP?PT-PNIPAM were able to form vesicles in water spontaneously.The effective association of small molecules and low-entropy chains not only enhances the ability in self-assembly of small molecules but also endows homopolymeric low-entropy chains with the ability in forming high-curvature structures.More importantly,the driving force of self-assembly was contributed by feeble ?-? interaction among small molecules and van der waals,pole-pole interactions between low-entropy chains,free of solvophobic effects.This robust strategy provides easy access to biocompatible,multi-stimuli responsive vesicles,impermeability-tunable nanoreactors,and self-healing materials with proper mechanical stiffness and dynamic healing ability from nonamphiphilic architectures.