Study On The Properties Of Functional Polydiacetylene Assembles

Due to the presence of longÏ€-conjugated system and can be very easy to self-assemble into various forms of assembly, polydiacetylene derivatives have been recognized as one of the most promising materials in optical, electrical and biological devices applications. By designing the functional diacetylene monomers and changing the molecular structure of diacetylene to control the polydiacetylene supramolecular assembly structure at the molecular level and study on the relationships between the different assembly structure and its properties.In order to investigate the exact effect of stereoregular packing of head group in the side chain on the helical structure formation of polydiacetylene backbone, the larger size of bisazobenzene-substituted diacetylene monomer, 4-(4-nitrophenylazo) azobenzene-10, 12-pentacosadiynoate (BNADA) was synthesized successfully. Owing to overcrowded packing of bisazobenzene chromophores, the BNADA Langmuir-Blodgett (LB) films showed macroscopic supramolecular chirality, although BNADA molecules were achiral. Under circularly polarized UV light (CPUL) irradiation, supramolecular helix of bisazobenzene chromophores always maintained, due to the large size and lower photo-isomerization rate of bisazeobenzene chromophores. While for polydiacetylene backbone, the helical direction of the polymer chain should be decided by the competition of the effect of stereoregular packing of bisazobenzene chromophores and the interaction between the CPUL and the diacetylene dimer.A novel crown functionalized diacetylene monomer, N-(2, 3, 5, 6, 8, 9, 11, 12-octahydrobenzo [b] [1, 4, 7, 10, 13] pentaoxacyclopentadecin-15-yl) pentacosa-10, 12-diynamide (BCDA), was synthesized successfully. The copolymerized composite vesicles of BCDA and 10, 12-pentacosadiynoic acid (DA) with embedded receptor sites for metal ions have been prepared and characterized. Their response to the presence of metal cations in aqueous solution has been investigated by monitoring changes of color and UV-vis absorption. Upon addition of a serial of alkali, alkaline earth and transition metal cations such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Fe²⁺, Co²⁺, Cu²⁺, Mn²⁺, Ba²⁺, Cd²⁺, Ag⁺, Pb²⁺ and Zn²⁺, only Pb²⁺ ion could induce a color change from blue to red observable by the naked eye, which clearly showed that PBCDA/ PDA composite vesicles could act as a highly selective and sensitive probe to detect Pb²⁺ ion in aqueous solution with minor interference from other metal ions. The excellent Pb²⁺ ion selectivity of PBCDA/PDA composite vesicles were mainly attributed to the stronger complexation behavior of Pb²⁺ with crown ethers and carboxylic acid at the lipid-solution interface which could perturb the polydiacetylene backbone.