Study On The Solid Polymerization Of Diacetylene And The Properties Of The Polydiacetylene Assembles

On account of the presence of longÏ€-conjugated system,polydiacetylene has been recognized as one of the most important non-linear optical and electron transport materials for a long time.The properties of high nonlinear optical susceptibility. ultrafast optical response,unique photo-conduction properties and strong chromogenic transitions render polydiacetylenes one of the most promising materials in optical,electrical and biological devices applications.In this work,some efforts have been made to sensitize solid-state polymerization of diacetylene in visible light region.Then the achiral azobenzene substituted diacetylene were assembled into chiral supramolecular systems in two-dimensional interface.Moreover,colorimetric response of azobenzene-terminated polydiacetylene vesicles under thermal and photic stimuli has been investigated in detail.10,12-Pentacosadiynoic acid(PCDA) hybrid films with various loadings of a ruthenium(â…¡) complex([Ru(dpphen)₃]Cl₂)(0.5 to 4.6 mol%) were prepared by spin-coating.Solid-state polymerization of diacetylene monomers can be sensitized in the visible light region by embedding[Ru(dpphen)₃]Cl₂ into the hybrid films.In situ absorption measurement enables us to study the polymerization kinetics of PCDA monomers in the hybrid films.The polymerization process can be described by a first order rate equation and the polymerization rate constants are determined and discussed in detail.The mechanism of the sensitization is discussed,and an explanation based on photo-induced electron transfer from[Ru(dpphen)₃]Cl₂ to PCDA moiety is presented.Strong quenching of[Ru(dpphen)₃]Cl₂ fluorescence was observed even at a low monomer conversion.Enhancement of polydiacetylene(PDA) fluorescence could be observed in the presence of[Ru(dpphen)₃]Cl₂.The mechanism of energy migration from the[Ru(dpphen)₃]Cl₂ molecules to the polymer chains is also presented.Moreover,to explore the electron transfer and energy migration mechanisms in ruthenium complex/polydiacetylene systems is of great fundamental important for the rational design of novel electroluminescence devices and optical sensors.A series of diacetylenic monomers containing azobenzene chromophores with different terminal groups(NADA,CADA,MADA) were synthesized and characterized by ¹H NMR.The monolayer of azobenzene substituted diacetylenic monomers have been transferred onto the solid substrate by the traditional Langmuir-Blodgett(LB) method.The surface morphologies of polymerized monolayer films were obtained by AFM.Solid-state polymerization of LB films can be sensitized in visible light region.In situ UV-vis absorption measurement enables us to study polymerization kinetics of their LB films.The polymerization process can be described as a first order rate equation and polymerization rate constants are characterized in detail.Furthermore,achiral NADA molecules can form chiral LB films through overcrowded packing of the azobenzene moiety.moreover,control and modulation of chirality for azobenzene-substituted polydiacetylene LB films with circularly polarized UV light were reported.P-nitro azobenzene substituted diacetylene(NADA) vesicles are prepared and characterized in detail by means of transmission electron microscopy(TEM) as well as UV-vis absorption spectra.NADA vesicles can be polymerized upon UV irradiation and their polymerization kinetics behavior could be described as a first order reaction.The size of the polymerized NADA(PNADA) vesicles is around 180 nm.PNADA vesicles show enhanced stability and completely reversible thermochromic response.And we establish the links between thermochromic transition reversibility and the strength of intermolecular interaction among side chains within PNADA vesicles matrix by means of Fourier transform infrared spectroscopy(FTIR) as well as UV-vis absorption spectra.PNADA/PDA complex vesicles show partially reversible thermochromic response.All above results indicate that strong intermolecular interaction among azobenzene mesogens within the vesicles is essential for the enhanced stability and completely reversible thermochromic transition.Novel partially reversible photochromism for PNADA/PDA complex vesicles are reported for the first time.PNADA/PDA complex vesicles show tunable chromatic switch from blue to red in response to 365 nm light irradiation.After subsequent irradiation with 435 nm light,this blue-to-red chromatic transition could be partially recovered.The explanation based on the photo-isomerization of azobenzene chromophores was proposed.