Reversibility between glass and melting transitions of poly(oxyethylene)
Abstract
The heat capacities, C{sub p}, of poly(oxyethylene), POE, with molar masses from 1500 to 900,000 Da, were analyzed by differential scanning calorimetry (DSC), quasi-isothermal, temperature-modulated DSC (TMDSC), and wide-angle X-ray diffraction (WAXD). There is no change in crystal structure before melting, but the lattice parameters increase rapidly in the melting region. Perfected extended-chain and once- or twice-folded crystals of the oligomers with a molar mass above 1100 Da melt practically fully irreversibly and permit direct measurement of the thermodynamic C{sub p}. The folded-chain crystals of high molar mass show some locally reversible melting. The reversing, apparent C{sub p} depends on molar mass and amplitude and frequency of modulation. After separation from the latent heat effects, the reversible, thermodynamic C{sub p} depends on the melting temperature for low molar masses and increases beyond the vibrational C{sub p} due to conformational motion. Molar masses of 8000-20,000 have almost the same C{sub p}. These observations permit a quantitative discussion of the thermodynamic C{sub p} and the locally reversible melting of the globally metastable POE in the melting range. The increase in C{sub p} between 250 K and the melting temperature is interpreted as a glass transition within the crystal.
- Authors:
-
- University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)
- University of Tennessee, Knoxville (UTK)
- Publication Date:
- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1003246
- DOE Contract Number:
- DE-AC05-00OR22725
- Resource Type:
- Journal Article
- Journal Name:
- Macromolecules
- Additional Journal Information:
- Journal Volume: 38; Journal Issue: 1
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 36 MATERIALS SCIENCE; AMPLITUDES; CALORIMETRY; CRYSTAL STRUCTURE; GLASS; LATTICE PARAMETERS; MELTING; MODULATION; TEMPERATURE DEPENDENCE; THERMODYNAMICS; X-RAY DIFFRACTION
Citation Formats
Qui, Wulin, Pyda, Marek, Nowak-Pyda, Elisabieta, Habenschuss, Anton, and Wunderlich, Bernhard. Reversibility between glass and melting transitions of poly(oxyethylene). United States: N. p., 2005.
Web.
Qui, Wulin, Pyda, Marek, Nowak-Pyda, Elisabieta, Habenschuss, Anton, & Wunderlich, Bernhard. Reversibility between glass and melting transitions of poly(oxyethylene). United States.
Qui, Wulin, Pyda, Marek, Nowak-Pyda, Elisabieta, Habenschuss, Anton, and Wunderlich, Bernhard. 2005.
"Reversibility between glass and melting transitions of poly(oxyethylene)". United States.
@article{osti_1003246,
title = {Reversibility between glass and melting transitions of poly(oxyethylene)},
author = {Qui, Wulin and Pyda, Marek and Nowak-Pyda, Elisabieta and Habenschuss, Anton and Wunderlich, Bernhard},
abstractNote = {The heat capacities, C{sub p}, of poly(oxyethylene), POE, with molar masses from 1500 to 900,000 Da, were analyzed by differential scanning calorimetry (DSC), quasi-isothermal, temperature-modulated DSC (TMDSC), and wide-angle X-ray diffraction (WAXD). There is no change in crystal structure before melting, but the lattice parameters increase rapidly in the melting region. Perfected extended-chain and once- or twice-folded crystals of the oligomers with a molar mass above 1100 Da melt practically fully irreversibly and permit direct measurement of the thermodynamic C{sub p}. The folded-chain crystals of high molar mass show some locally reversible melting. The reversing, apparent C{sub p} depends on molar mass and amplitude and frequency of modulation. After separation from the latent heat effects, the reversible, thermodynamic C{sub p} depends on the melting temperature for low molar masses and increases beyond the vibrational C{sub p} due to conformational motion. Molar masses of 8000-20,000 have almost the same C{sub p}. These observations permit a quantitative discussion of the thermodynamic C{sub p} and the locally reversible melting of the globally metastable POE in the melting range. The increase in C{sub p} between 250 K and the melting temperature is interpreted as a glass transition within the crystal.},
doi = {},
url = {https://www.osti.gov/biblio/1003246},
journal = {Macromolecules},
number = 1,
volume = 38,
place = {United States},
year = {Sat Jan 01 00:00:00 EST 2005},
month = {Sat Jan 01 00:00:00 EST 2005}
}