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Title: 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:
 [1];  [2]
  1. University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)
  2. 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}
}