engleski

Investigation of relaxations in polystyrene-polyoxyethylene copolymer by thermally stimulated current

The diblock copolymer containing 43.5 wt.% of polystyrene (PS) (Mw=15000) and polyoxyethylene (POE) (Mw=19500) was investigated by integral and by partial thermally stimulated depolarization current (TSDC) measurements in the temperature range 173 K – 293 K. First peak P1 widely distributed from 183 K to 213 K was a dipolar peak attributed to the initial part of the glass transition in POE. The next P2 peak with the maximum at 273 K was due to the glass transition. The third P3 peak with maximum at about 263 K was caused by the space charge relaxation localized at the interfaces between the ordered and nonordered phases in POE, Maxwell-Wagner relaxation, representing a precursor in melting of POE crystals. The results were supported by determination of activation energy Ea of the partial peaks, which covered the whole range of investigation, and by DSC measurements. The Ea (T) distribution showed the maximum in entropy change at 219&plusmn ; ; ; 4 K. Some runs with samples containing different amount of PS component were considered. All the relaxations were coming from the POE block. The current due to PS slightly overlapped the total spectra without interaction. The influence of the repeated runs was observed and discussed.

Polystyrene-polyoxyethylene copolymer; Thermally stimulated current; Activation energy.

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