Gas Sensitive Materials Based On Polyaniline/Macromolecule Composites

Ammonia sensor is one of the important products of gas sensor. It is widely used in every aspect of social life and every research field. Among them, conducting high polymer ammonia sensor is becoming the focal point studied at present because of its convenient preparation method, excellent gas sensitivity property and operating conditions easy to implement.We improved the ammonia sensitivity property of gas sensitive material by using different materials doped PANI. And it was made with a better selectivity, reaction time and sensitivity to NH3. The main research contents are as follows:1. PMMA/PANI composites have been synthesized by using polymethyl methacrylate (PMMA) as dopant and ammonium persulfate (APS) as oxidant. The new-type polymer regards PMMA as the nuclear and PANI as the surface layer. The results showed that the new-type polymer had a better sensitivity to NH3 at room temperature. The impact of different factors on emulsion stability and gas sensitivity property of PANI/PMMA composites was studied by controlling the variables. The preferred experimental conditions were decided preliminary:n (DBSA)/n (An)= 1.5; n (APS)/n (An)= 1.2; w (PMMA)/w (An)=4; polymerization time 18h, the sensitivity to 1 OOOppm NH3 reached 24.7 under this condition.2. PANI/PEG composites were synthesized with polyethyleneglycol (PEG) as dopant and ammonium persulfate (APS) as initiator by one-step emulsion polymerization. The impact of different factors on emulsion stability and gas sensitivity property of PANI/PEG composites was studied by controlling the variables. The optimal experimental parameters were obtained:n (DBSA)/n (An)=1.0, n (APS)/n (An)=1.0, n (PEG) /n (An)=2, polymerization time 16h. The results indicated that the gas sensor sensitivity to 1000ppm NH3 reached 43.8 at room temperature.3. The stable emulsion PANI/PVAC composites were synthesized with Polyvinylacetate (PVAC) as dopant, ammonium persulfate (APS) as initiator and DBSA as emulsifier. The optimum experimental parameters were obtained by using single factor experiment:n (DBSA)/n (An)=1.0:n (APS) /n (An)=1.0:n (VAC)/n (An)=1.0:polymerization time 6h; reaction temperature 20℃. Under this condition, the sensitivity to 1000ppm NH3 reached 56.0.4. The structural change and thermal stability of doped PANI before and after meeting NH3 was studied by adopting infrared spectroscopy technology and TG technology. It is laying foundations for the further study and application on polyaniline composites.