The Preparation And Study The Sensing Properties Of Functional Polydiacetylene Assemblies

Polydiacetylene(PDA),as a kind of stimuli-responsive conjugated polymer,which could be prepared by diacetylene monomers upon topochemical polymerization process.Diacetylene monomers can be chemically modified or functionalized and can easily form different self-assembled systems.Almost all the self-assembled systems of diacetylene monomers including liposomes,vesicles,films,crystals,microtubes,fibres or gels can be polymerized to form PDA with irradiation by y-radiation,UV light,or heating treatment.PDA exhibits strong color variations from blue to red as well as fluorescence changes with external stimuli(solvents,ions,pH,temperature,stress,etc.),which is ascribed to the disruption of the effective conjugation length of backbone chains.Therefore,it is of great value to the synthesis the novel diacetylene monomers and the utilization of smart properties for the fabrication of chemosensors.In this article,three functionalized diacetylene monomers were synthesized and the hybrid liposomes probes were prepared by the sonication method.The basic optical and sensor properties were researched in this work.Moreover,the basic mechanism for the recognition of Pb2+,volatile organic compounds(VOCs)or chiral lysine amino of fluorescent probes were also studied in this article.(1)Polydiacetylene monomer(PCDA-pBA)modified with phenylboronic acid was synthesized.Composite vesicles were prepared by assembling PCDA-pBA with 10,12-pentacosadiynoic acid(PCDA)at a molar ratio of 1:4.In the presence of Pb2+,the composite vesicle presented a color change from blue to red with the increase of fluorescence intensity realizing high specific detection of Pb2+ in aqueous solution.Pb2+ reacted strongly with phenylboronic acid groups and carboxylic acid groups to form metal complexes,which could disturb the backbone of PDA chains,leading to color change and fluorescence emission.In brief,the quantitative analysis of Pb2+ can be realized based on the linear relationship between Pb2+ concentration and the fluorescence intensity of vesicle.(2)A kind of colorimetric and fluorescence sensor based on histidine-functionalized polydiacetylene(His-DA)to detect Pb2+ and VOCs was established.Composite vesicles were prepared by assembling His-DA with PCDA at a molar ratio of 1:4.Compared with other metal ions,the composite vesicles showed blue-red color transition only after adding Pb2+,which was attributed to the conformation transition of the conjugated backbone.The system has higher sensitivity and lower limit of detection.At the same time,the PDA films prepared by histidine-functionalized diacetylene monomer had a colorimetric response to most VOCs.Different color changes could be seen with the naked eye though the PDA films,which had obvious practical advantages.(3)Fluorescein-functionalized diacetylene monomer(F-DA)was prepared by chemical modification.The PCDA and F-DA were assembled at a molar ratio of 12:1 to prepare composite vesicles.When equal amounts of L-Lysine or D-Lysine were added to the composite vesicle respectively with a certain concentration of Cu2+,the vesicle presented the color change from blue to purple and blue to red respectively,and the corresponding absorption spectra were also different,so that the composite vesicles realized the chiral recognition of lysine enantiomers.The logical operations of "AND" and "OR" logic gates were constructed in this system by taking different permutations and combinations of stimuli as input signals,and vesicle color changes as output signals.