Free Volume Expansion of Poly[1-(trimethylsilyl)-1-propyne] Treated in Supercritical Carbon Dioxide As Revealed by Positron Annihilation Lifetime Spectroscopy
The free volume changes of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) treated in supercritical CO2 (scCO2) were investigated with positron annihilation lifetime spectroscopy (PALS). CO2 is known to plasticize and increase the free volume size of a broad range of polymers. In this work dense PTMSP fi...
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Published in | Macromolecules Vol. 44; no. 8; pp. 2766 - 2772 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Washington, DC
American Chemical Society
26.04.2011
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Subjects | |
Online Access | Get full text |
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Summary: | The free volume changes of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) treated in supercritical CO2 (scCO2) were investigated with positron annihilation lifetime spectroscopy (PALS). CO2 is known to plasticize and increase the free volume size of a broad range of polymers. In this work dense PTMSP films were treated with scCO2 under different pressures and temperatures, resulting in the enlargement of the characteristic channel-like holes (R 3) and the larger free volume cages (R 4) up to 39% and 19%, respectively. The free volume enlargement was found to have a relaxation time of ∼30 years. At higher temperatures (110−150 °C), the o-Ps intensities and gel permeation chromatography (GPC) data revealed chemical changes of the scCO2-treated polymer due to the onset of PTMSP’s degradation. However, at lower temperatures (40−70 °C), significant free volume cavity size increases to 25% for R 3 and 9% for R 4 were also observed. |
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ISSN: | 0024-9297 1520-5835 |
DOI: | 10.1021/ma1029345 |