Synthesis Of Hyperbranched Fluorescent Porous Polymer (HFPPs) And Sensing Performance For Nitroaromatics

Over the past decade,terrorist attacks and security issues occur frequently all over the world.Rapid and reliable detection of explosives at a safe distance is an important challenge for technology.Such as 2,4,6-trinitrotoluene(TNT)and 2,4-dinitrotoluene(DNT)is not only the main ingredient of commonl explosives,but also important environmental pollutants.Thus,fast and sensitive,on-site field testing of nitroaromatics have great significance for security,industrial process control and environmental monitoring supervision.Today,the field of chemical sensing is becoming increasingly dependent on generating of new material.Polymer,crystal structure,glass materials,particulate materials and nanostructures and so on to the sensor has made a profound impact,and also give sensing system to superior performance.Fluorescence detection methods based on electron transfer mechanism or energy transfer mechanism or combination of both whether in solution or in the solid state,More and more attention due to its advantages of sensitivity,portability,low cost,short reaction times,compatibility.There are homogeneous fluorescent sensors applied in the solution detect target analytes by capturing the change of fluorescence of the solution,and with good selectivity,high sensitivity,fast response,etc.,but less practicality.And Fluorescent film sensors for detecting analytes in the gas phase,which eliminate the pollution for analytes,reusable,high practicality.However,many factors can affect the sensoring.For linear conjugated polymer film made of spin coating,the thickness of the fluorescence sensor is the most influential factor,too thick will affect the diffusion of analyte molecules,too thin will cause the Testabilit y of sensors' fluorescence decreased.For fluorescent monolayer sensors by grafted on the glass,it is not only poor testability due to the disadvantage of too thin,but also have photobleaching.These disadvantages greatly affected the sensoring of the sensors.A hyperbranched polymer P with adamantane as core and diphenyl ethynyl pyrene as tether was synthesized.The three-dimensional structure and rigid molecular skeleton of adamantane make the polymer porous.The results showed that the polymer P exhibited uniform slit pore structure,the aperture distribution was about 10 nm,belonging to mesoporous materials.The comonomers diphenyl ethinyl pyrene(M)was also synthesized to study its optical properties and investigate the fluorescence quenching properties for nitro-aromatics.Compared with the monomer M,polymer P showed a larger Stokes shift,the quenching efficiencies at equilibrium was almost the same in TNT solution.However,in the saturated DNT vapour,the quenching efficiencies of the P and M spin-coated film prepared under the same conditions were 82% and 22%,respectively,which demonstrated that the porous of polymer P made its permeability greatly improved.In addition,a series of different thickness of the film with different polymer concentrations were prepared.We found that the emission spectra exhibited remarkable red-shifts with the film thickness increased,however,the quenching efficiencies in saturated DNT vapor changed little.The mesoporous structural overcome the dependence of the quenching efficiencies for the spin-coating film sensor on thickness.