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Studies on degradation of poly(ethylene oxide) by multistep pyrolysis/gas chromatography with a programmable temperature vaporization injector.

100%

Kaczmarek H. , Kowalonek J. , Janssen H. G. , Lieshout H. P. M. v.

tom T. 45, nr 6

433-438

The multistep pyrolysis/gas chromatography technique using a programmable temperature vaporization injector was used to study thermal and photochemical properties of polymers. Pure poly(ethylene oxide) (PEOX) and PEOX + 3% CoCl2 specimens, 20-mm films, were UV-irradiated (2.45 mW/cm2) for 2 and 4 h in air at room temperature and pyrolyzed/gas chromatographed at 200oC, 420oC and 500oC (Fig. 1, 2). The products evolved at 200oC included residual solvent, monomer, catalyst, polymerization additives, and processing aids. At 420oC, degradation attained maximum and the compound concentrations were maximum in PEOX UV-irradiated for 2 h. In the 4-irradiated PEOX, the 420oC chromatographic peaks were less intense. At 500oC, the intensity of the peaks rose as the irradiation time was prolonged. CoCl2 (3%) gave rise to new degradation products. At 420oC and 500oC, irradiation had negligible effect on degradation of PEOX + 3% CoCl2. Scheme 1 illustrates the major interactions accompanying thermal and photochemical degradation of PEOX in the presence of CoCl2.

In-situ study of the influence of crystallization on the ionic conductivity of polymer electrolytes

80%

Marzantowicz M. , Dygas J. R. , Krok F. , Zygadło-Monikowska E. , Florjańczyk Z.

Materials Science Poland

2006

tom Vol. 24, No. 1

195--203

Simultaneous impedance measurements and optical observations of polymer electrolytes were conducted in an automated experimental setup, combining an impedance analyser, polarizing microscope with a heating stage and a digital camera. The polymer film was placed between glasses with indium tin oxide conductive layers, forming a transparent cell mounted in a custom-designed holder, which preserved an argon atmosphere. Results of in-situ studies for various compositions of poly(ethylene oxide) (PEO) with LiN(CF3SO2)2 salt (LiTFSI), as well as pure PEO, are presented. In the investigated systems, crystallization had a strong impact on ionic conductivity. It was found that the initial growth of crystalline structures caused only a small fraction of the total decrease of conductivity. A large decrease in conductivity was observed during the second stage of crystallization, when no significant changes in microscope picture were observed. In pure PEO and the PEO:LiTFSI 6:1 system, a dense crystalline structure developed, resulting in a decrease in conductivity of over two orders of magnitude. In dilute PEO:LiTFSI systems, a "loose" structure was formed, with amorphous areas preserved between crystallites, and conductivity decreased by only a factor of about 6.