Construction And Properties Of Multiple Stimuli Responsive Supramolecular Polymers

Supramolecular polymers are polymeric arrays of repeating units held together by highly directional noncovalent interactions such as multiple hydrogen bonding,π-πstacking interactions,metal coordination,electrostatic interactions,host-guest interactions,and so forth.The assembly-disassembly process of supramolecular polymers is very easy to happen,because non-covalent bond has good reversibility.Supramolecular polymers are multiple-stimuli responsive to the external stimuli,such as temperature,pH,light and competitive components.The fluorescence properties,and the structure of the polymer will change with the chang of external stimulis.Because of the unique properties,the supramolecular polymers have been applied to many fields,such as drug delivery,chemosensors,cellular imaging,photosensitive material,and so on.In this dissertation,we focus on the construction and characterizaiton of multiple stimuli-responsive supramolecular polymers.The following is the summary of each part of work.Firstly,we designed and synthesised a linear supramolecular chain.P1 was produced by the click reaction of the monomer 1 and 2.Monomer 1 contains two alkynes and one terpyridyl,and monomer 2 contains two tetraphenylethylenes（TPE）,one disulfide bond and two asides.By adding Zn²⁺ionsinto the CHCl₃/CH₃CN mixture of P1(three-dimensional cross-linked network of supramolecular polymer gel was obtained,because of metalcoordination interactions between Zn²⁺ions and terpyridyl.Meanwhile,because TPE has the effect of aggregation-induced emission,the fluorescence intensity was enhanced significantly.However,with the addition of competive ligand of cyclen,heating,or the reductant of DTT,the gel was transformed into sol together with the decrease of the fluorescence intensity..Secondly,design and synthesis of a crown ether-based host molecule H1,containing triphenylamine group and a guest molecule P2 with coumarin and quaternary ammonium groups in its side chain by free radical polymerization.The fluorescence of the host molecule was quenched when encountered metal Fe³⁺ion,and the detection limit for metal Fe³⁺ions is as low as 0.1875μM.So the molecule can be used in the detection of Fe³⁺ions.In addition,P2 and H1 in the mixture of CHCl₃and CH₃CN can form supramolecular polymers by self-assembly for the host-guest interactions.Since the host molecule contains TPA group,which has AIE property and the guest molecule contains coumarin group,which has ACQ property,the supramolecular polymer all has excellent fluorescence properties under dilute or concentrated solution.