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Authors
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Dlubek, G. ; Pionteck, J. ; Kilburn, D.
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Title
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The Structure of the Free Volume in Poly(styrene-co-acrylonitrile) from Positron Lifetime and Pressure Volume Temperature (PVT) Experiments. I. Free Volume from the Simha-Somcynsky Analysis of PVT Experiments
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Date
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12.03.2004
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Number
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11597
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Abstract
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<B>Summary:</B> The structure of the free volume and its temperature dependence between 25 and 190 °C of copolymers of styrene with acrylonitrile, SAN (0 to 50 mol-% AN), is studied by pressure volume temperature (PVT) experiments and positron annihilation lifetime spectroscopy (PALS). In this first part of the work, PVT data are reported which were analysed with the Simha-Somcynsky equation of state (S-S eos) to estimate the volume fraction of holes, <I>h</I>, which constitute the excess free volume. The temperature and pressure dependence of the specific volume <I>V</I>, the specific occupied and free volume, <I>V</I><SUB>occ</SUB> = (1 - <I>h</I>)<I>V</I> and <I>V</I><SUB>f</SUB> = <I>hV</I>, and the corresponding isobaric expansivities and isothermal compressibilities for both the rubbery and glassy state, are estimated. We obtained the unexpected results that (i) the occupied volume changes its coefficient of thermal expansion at <I>T</I><SUB>g</SUB> from <I><IMGSRC="/giflibrary/12/alpha.gif"BORDER="0"></I><SUB>occ,g</SUB> <IMGSRC="/giflibrary/12/ap.gif"BORDER="0"> 0.5<I><IMGSRC="/giflibrary/12/alpha.gif"BORDER="0"></I><SUB>g</SUB> <IMGSRC="/giflibrary/12/ap.gif"BORDER="0"> 1 × 10<SUP>-4</SUP> K<SUP>-1</SUP> below <I>T</I><SUB>g</SUB> to almost zero above <I>T</I><SUB>g</SUB> and (ii) the isothermal compressibility of the occupied volume at zero pressure is rather high, <I><IMGSRC="/giflibrary/12/kappa.gif"BORDER="0"></I><SUB>o<br />cc</SUB> <IMGSRC="/giflibrary/12/ap.gif"BORDER="0"> 2 × 10<SUP>-4</SUP> MPa<SUP>-1</SUP>, and decreases only slightly at <I>T</I><SUB>g</SUB>. The variation of total, occupied, and free volume parameters with the composition of the SAN copolymers is discussed.
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Publisher
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Macromolecular Chemistry and Physics
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Wikidata
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Citation
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Macromolecular Chemistry and Physics 205 (2004) 500-511
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DOI
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https://doi.org/10.1002/macp.200300103
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Tags
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