Electrically Conducting Compatible Blends of Polyaniline / Poly(Vinyl Pyrrolidone)
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of ammonium hydroxide. Based on results from many similar syntheses, Mn is approximately 25,000 g/mole. PVP of three different molecular weights was used. High molecular weight (1,000,000 g/mole), designated PVP-M, and low mw (10,000 g/mole - PVP-IOK) were used as received from Polysciences. Low mw PVP (approx. 8000 g/mole - PVP-8K) synthesized in our lab by free radical polymerization of N-vinyl pyrrolidone was also used. PAn was dissolved in either N-methyl pyrrolidone (NMP) or dimethyl acetamide (DMAc) at 20 mg/ml by first stirring overnight, then sonicating the solution for about 8-10 hours. The solution had some fine particulates; filtering through a 2 .tm filter, then a 0.45 gtm filter removed these. PVP was also dissolved in either DMAc or NMP, then filtered through a 0.22 jim filter. Various concentrations of PVP were used for comparisons. Appropriate ratios of the two solutions were mixed to give the desired compositions. Several series of blends were cast, including spin-coated films and static-cast films, from all three PVP types, and with both solvents. Thinner films (60 jtm and less), used for light microscopy and conductivity measurements, were dried in a vacuum oven at 70-100°C for at least one day. Thicker films (0.3 mm), used in the thermal analysis (DMA, DSC, and TGA) and SAXS, were dried for several days under vacuum at 70-1000 C. Thermogravimetric analysis, TGA, was run on 10 mg samples in a Seiko TG/DTA-320. The samples were run from 30-510'C, 20'C/min. under a nitrogen purge. Differential scanning calorimetry, DSC, was done using a Perkin-Elmer DSC-7. To further dry the samples, and erase any thermal history, the samples were run up to 220 0 C in the DSC, and held for one minute under a nitrogen purge. The samples were then cooled to 10'C, and scanned from 10-2200 C at 20°C/min. Dynamic mechanical analysis, DMA, was run on a Seiko DMS-200 using small strips 25 mm long, 5 mm wide, and 0.3 mm thick. The samples were run in tension mode from 20220'C, 20 C/min., and five frequencies were scanned, 1, 2, 5, 10, and 20 Hz. These same films were used for small angle x-ray scattering (SAXS) measurements. A sample-to-detector distance of 272 cm enabled a scattering angle (20) collection range of approx. 0.160 to 1.05'. This corresponds to a d-spacing range of 540-84A. All conductivities were measured in air (low relative humidity, ranging from 17-27) by the van der Pauw four corner probe method. RESULTS AND DISCUSSION Several series of PAn/PVP compositions were blended, varying both the solvent and the PVP molecular weight. For PVP-10K, the two polymers were soluble in both solvents for all PAn:PVP-OK ratios prepared (up to 30 wt% PAn). PAn and PVP-M were soluble in NMP for all ratios of PAn:PVP-M (0-100% PAn). PVP-M and PAn together were not miscible in DMAc, even though both polymers were soluble in DMAc before blending. Mixing in DMAc resulted in the immediate formation of a thick PVP-M/PAn gel, regardless of the fraction of PAn. For a DMAc/NMP mixture, the blend would only remain in solution if the fr
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