Photopolymerization Of 2,2'-bis-halogen-bis-(3,4-ethylenedioxythienyl)phenylmethylene

Since the conductive polyacetylene was discovered in 1977,conjugated polymers gradually become one of the hottest research areas in modern materials science.Due to its semiconductor properties,as well as energy level and energy band controllable characteristics,conjugated polymers are widely used in modern organic electronics,replacing inorganic semiconductors for Field Effect Transistors,polymer solar cells,electroluminescentdevices,electrochromic devices and other fields.In the past decade or so,conjugated polymer sensors taked the attention of researchers?A number of sensors have been developed for anion and cation in solution.The polymer structure change which caused by the intermolecular interactions of analyte and functionalized branch of conjugated polymers perturbed the energy level of polymers,changed the absorption and fluorescence spectrum of the polymer to give signals,complete the test.As type of free radical polymerization,photopolymerization produces reactive free radical by illumination,then the radical take reactions with monomers.The dynamic process of photoinitiated polymerization in solution has been investigated clearly,Meanwhile,the photopolymerization reaction is widely used in coatings,inks and other fields.The kinetic of a limited number of solid state photopolymerization(topology polymerization)has also been studied more thoroughly.Little progress concerning of photopolymerization for halogenated thiophene derivatives is reported.It is generally believed that this kind of reaction cleaves the carbon-halogen bond by light and generates free radical to initiate reactions.In this paper,two monomers named 2,2'-bis-halogen-bis-(3,4-ethylene--dioxythienyl)phenylmethylene were synthesized and they were subjected to UV-polymerization.It was found that different substituted halogens resulted in the infrared and ultraviolet absorption spectra of the polymer.The neutral state polymer can be served as sensor with the detection limit to 50 ppm.It is noted that the polymers obtained through UV-polymerization are not stable under high concentration of halogen solution.Moreover,The kinetics of monomers photopolymerization was explored.The results show that the monomer reaction rate is 1/2,and the apparent reaction rate constants of the two monomers at UV-254 nm are close to each other.In addiiton,these monomers have similar reaction rate.