| Copolymers of 4-vinylpyridine(4VP) with nbutyl methacrylate(nBuMA) (4-VP-co-BuMA) and methacryloxyethyl butyl ammonium bromide with active organosilicone monomer (MEBA-co-Si) were prepared by radical copolymerization, and characterized by IR and element analysis.Resistive type thin film humidity sensors were prepared using quaternized 4-VP-co-BuMA as humi-sensitive materials, and the effects of composition of copolymer, quaternization time, electrode structures, technical parameters for preparation of sensors (including dipping time, concentration of dipping solution, etc.) on humidity response of sensors were investigated. It was found that introduction of hydrophobic monomer into polymer chain improved the response linearity and sensitivity, and the impedance of sensors decreased with longer quaternization time and shorter distance between electrode tracks.4-VP-co-BuMA quaternized with octyl bromide were found to be humi-sensitive material with good linearity, high sensitivity, fast response, high stability at high humidities. Sensors based on 4-VP-co-BuMA (4-VP/nBuMA=2/l) quaternized for 11 hours show good humidity response: Its logarithm of impedance varies linearly with relative humidity for four orders of magnitude(107-103 ) over the range of 33%RH~97%RH, showing high sensitivity, in addition, it exhibits fast response (response time less than seven seconds) and a small hysteresis(<2%RH). The response of sensors varied little after it was placed at high temperature(38癈), high humidity(87%RH~93%RH) with applied voltage of 200 mV for 72hours, which indicates the sensor has high stability under humid environment.Simultaneously cross-linked and quaternized 4-VP-co-nBuMA was also investigated as humidity sensing materials and showed good linearity, high sensitivity, good high stability at high humidity and high temperature, and durability to organic solvent, etc. Sensors based on 4VP-co-BuMA (VP/BuMA=l/l) with crosslinking and quaternization reaction of 17 hours exhibited a change of three orders of magnitude (104~107 ) in impedance over the range of 95%RH~30%RH, showing high sensitivity, and little hysteresis was observed.MEBA-co-Si was found to be humi-sensitive material with good linearity, highinAbstractsensitivity and fast response. Sensors based on nanocomposites of MEBA-co-Si with nanosized zinc oxide colloids was prepared, which show smaller impedance, good linearity, small hysteresis (<2%RH) and fast response (less than five seconds). Furthermore, its response changed little even after the sensor was soaked in water for 30 min.Four kinds of multi-layers nanocomposite humidity sensitive films, including sodium polystyrenesulfonate / poly(diallyldimethylammonium chloride) (NaPSS /PDDA), sodium polystyrenesulfonate/ poly4-vinylpyridine quaternized with butyl bromide (nBuBr-P4VP), sodium polysryrenesulfonate/zinc oxide(NaPSS/ZnO) and sodium poly(acrylic acid) /zinc oxide (PAANa /ZnO ), have been prepared by means of self-assembly. The UV -Vis spectra, contact angle test and AFM analysis indicated that all the films so prepared had a layer-by-layer structure. Transmission electron microscopy (TEM) analysis revealed that ZnO nanoparticles were equally distributed in the composite film.The humidity sensitive characteristics of these sensors prepared by means of self-assembly have been investigated and the effects of electrode structures, concentration of humi-sensing solution, number of bilayers, materials of the outer layer and inner layer on humidity response were discussed. It was found that self-assembly films of NaPSS/PDDA showed low impedance, good linearity and high sensitivity. Impedance of sensors with 25 bilayers of NaPSS/PDDA composite film changed linearly for four orders of magnitude (10 -10 Q) over the range of 20%RH~95%RH. Furthermore it was found that organic/inorganic nanocomposite films exhibit faster response than organic/organic composites.The humidity sensing behavior of sensors based on cross-linked and quaternized copolymer and the sensors based on nan...
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