Synthesis And Characterization Of HFIP Functionalized Hyperbranched Polysiloxane

Surface acoustic wave (SAW) chemical sensor is a kind of vapor sensor with thecharacteristics of fast response, good selectivity, small size and so on, which canoperate in situ and in real-time. It has been used widely to detect chemical warfareagents and explosives. The sensitive film and coating method play a critical role indeciding the performance of sensor. In this paper, the synthesis and adsorptionproperty of HFIP functionalized hyperbranched polysiloxane as coating material werestudied.In this study, methyl-bis(dimethylallylsiloxy)silane, that is AB2type siloxanemonomer was obtained through multi-step reactions. Then, hyperbranchedpolysiloxane was synthesized by AB2type monomer with the catalysis of theplatinum-carbon. It was found that the yield of one pot reaction was very low, and themolecular weight of product was small. In order to get polymer with large molecularweight, the best way is adding monomer by dropwise. It comes to the conclusion thatthe lower the speed of dropping, the larger the molecular weight of products is; themore the amount of monomer added, the larger polymerization degree will be.The target product was synthesized by hyperbranched polysiloxane andhexafluoroacetone (HFA), and it was characterized by IR, ion chromatograph andhydroxyl content analysis. The optimum reaction conditions were also studied, whenreaction was finished in15h, at25℃, with no solvent, hydroxyl content and fluorinecontent reached maximum.The HFIP functionalized hyperbranched polymer was coated on the SAW sensorpiezocrystal by spin coating method. In the gas supply system,2,4-dinitrotoluene wasused as simulation gas, and the responses of SAW sensor were tested. The conclusionis as follows: the adsorption property of coating improves with the polymerconcentration and its adsorption speed increases with hydroxyl content in polymer.