Synthesis And Self-Assembly Of Triphenylene-based Supramolecules And Amphiphilic Star Polymers

Supramolecular self-assembly is considered to be an efficient strategy to prepare functional materials,in which molecules associate spontaneously into ordered aggregates as a result of noncovalent interactions.The design of materials through self-assembly processes is becoming one of the primary frontiers of supramolecular chemistry.Otherwise,ionic bond is well known as the strongest noncovalent interactions and sensitive to pH.However,so far ionic interactions have largely been neglected in synthesis of supramolecules,especially for ion-bonded supramolecular star polymers,although they have some distinct characteristics,such as fast and facile functionalization,reversibility,self-reparability and environment sensitivity.In this thesis,we designed and synthesized a series of supramolecules by molecular recognition method,which was formed by combining discotic triphenylene derivatives and guest molecules through ionic interaction.Their self-assembly properties in solution were investigated.There are six main parts included in this thesis.The first part is concentrated on the synthesis a family of discotic supramolecular compounds consisting of 2,3,6,7,10,11-hexakis(N,N-dimethylaminopropylaminocarbonylmethoxy)triphenylene (HDTP) and 4-dodecyloxy-, 3,5-didodecyloxy-,and 3,4,5-tridodecyloxy-benzoic acids via molecular recognition. The structures of resulting products were characterized by Fourier transformation infrared(FTIR) spectra and proton NMR(¹H NMR) spectra.Moreover,their self-assembly behaviors in toluene were investigated by means of transmission electron micrograph(TEM) and UV-vis measurement.Discoctic supramolecular compound with mono-dodecyloxybenzoate units can make solvent gelation and large sheet-like structure was observed,while supramolecular compound with di-and tridodecyloxybenzoate moieties self-assembled into stable nanofibers with different length.It was suggested that the alkyl chains promoted the solubility of supramolecular compound but make against the formation of order aggregates. The second part shows a novel two-component organgelator.At first,an ion-bonded discotic supramolecular compound was successfully prepared from HDTP and 4'-dodecyloxybiphenyl-4-carboxylic acid(DBC) by ionic self-assembly route.We found that the supramolecular compound can self-assemble into stable gels in aromatic hydrocarbons,such as benzene,toluene,and xylene.Nanofibers with diameters of 50-130 nm were observed in the p-xylene gels by TEM and SEM.The FTIR data in conjunction with UV-vis and fluorescence spectra suggested that the aggregation of the complex into elongated fibers in solution was induced by a directional extended network of hydrogen bonds,Ï€-Ï€interactions and van der waals force.Based on the experiment analysis,we proposed a tentative self-assembly model of this two-component gel-phase material.In the third part,we chose two triphenylene-based derivatives with opposite charges,HDTP and 2,3,6,7,10,11-hexakis(carbonylmethoxy)triphenylene(HCTP),to achieve a novel two-component discotic supramolecule by molecular recognition. The structure was checked by FTIR and ¹H NMR.UV-vis together with FL measurement confirmed that the combination of ionic interactions andÏ€-Ï€interactions drove two building blocks to construct one-dimensional columnar stacks. TEM image showed a large three-dimensional fibrillar network from aqueous solution,which was composed by the long strands with micrometers in length and approximately 100-160 nm wide.The forth part describes theÏ€-conjugated template promoted the formation and self-assembly of well-defined polymer.HDTP was selected as template and combined with PEG-COOH via complementary molecular recognition to provide an ion-bonded discotic supramolecular star polymer HDTP/PEG-COOH.The structure of the resulting polymer was confirmed by ¹H NMR,FTIR and gel permeation chromatography(GPC).The self-assembly behaviors of the supramolecular polymer in deionized water,chloroform,and toluene were investigated.Spherical aggregations were observed by TEM in all solution.Their diameter increases with decrease of the polarity of solvent.UV-vis and fluorescence spectra indicated thatÏ€-Ï€interactions between aromatic units play important roles in the formation of aggregates. Fluorescence spectra in different solution further suggest that low polar solvent favorable to enhance more strong ionic bonds andÏ€-stacking interactions,and promote intermolecular overlapping of the triphenylene cores and supramolecular star polymer to tight aggregate.The study in the fifth part developed a novel strategy for the preparation of ion-bonded supramolecular star polymers by RAFT polymerization.An ion-bonded star supramolecule with six functional groups was prepared by molecular recognition between HDTP and trithiocarbonate carboxylic acid derivative,and used as RAFT agent in polymerization of tert-butylacrylate(tBA) and styrene(St).The obtained polymers were characterized by ¹H NMR and GPC.The results show that the polymerization possesses the characters of living free radical polymerization and the ion-bonded supramolecular star polymers PSt,PtBA,and PSt-b-PtBA with well-defined six-arms have been successfully synthesized.The ion-bonded supramolecular polymer was easily cleaved when the solution pH was changed.In the last part,a triphenylene(TP)-based six functional initiator was prepared and used for atom transfer radical polymerization of 2-(N,N-dimethylamino)ethyl methacrylate(DMAEMA) and styrene(St).The polymers were characterized by GPC, ¹H NMR and FTIR.The results show that the polymerization possesses the characters of living free radical polymerization,and well-defined six-armed star-shaped block copolymers TP(PDMAEMA-b-PSt)₆ bearing hydrophilic backbones inside and hydrophobic blocks outside were successfully synthesized.The self-assembly behaviors of amphiphilic star block copolymer in selective solvents were investigated by TEM and SEM.Coexisting spherical and bowl-shaped aggregates were observed in neutral aqueous solution,and large spherical structures with different dimension were obtained from self-assembly of the resulting copolymer in diluted HCl and CF₃COOH aqueous solution.The possible mechanism of the morphology formation was suggested.