Free Volume Expansion of Poly[1-(trimethylsilyl)-1-propyne] Treated in Supercritical Carbon Dioxide As Revealed by Positron Annihilation Lifetime Spectroscopy

• Published in: Macromolecules Vol. 44; no. 8; pp. 2766 - 2772
• Main Authors: Claes, Stan, Vandezande, Pieter, Mullens, Steven, Van Bael, Marlies K, Maurer, Frans H. J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 26.04.2011
• Subjects: Applied sciences; Chemical Sciences; Exact sciences and technology; Kemi; Natural Sciences; Naturvetenskap; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis; Structure processing relationship; Conjugated polymer; Supercritical carbon dioxide; Physical dressing; Carbon dioxide; Supercritical solvent; Free volume; Acetylene derivative polymer; Positron annihilation; Experimental study; Functional polymer; Silicon polymer
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma1029345

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.