Free volume in PEP-silica nanocomposites with varying molecular weight
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- 作者：Christian Ohrt ; T枚njes Koschine ; Klaus R盲tzke ; Franz Faupel ; Lutz Willner ; Gerald J. Schneider
- 关键词：Polymer nanocomposites ; Free volume ; Positron annihilation lifetime spectroscopy
- 刊名：Polymer
- 出版年：14 January, 2014
- 年：2014
- 卷：55
- 期：1
- 页码：143-149
- 全文大小：556 K
文摘
The influence of confinement in polymer-nanocomposites on free volume and glass transition of the polymer chains was studied. The molecular weight (Mw) of poly(ethylene-alt-propylene) (PEP) was varied from 3k to 200k and so the end-to end distance of the chains at fixed diameter (鈭?5聽nm) and concentration (15%) of the silica nanoparticles increased. Thus the topological confinement increases with increasing Mw. Using hydrophobic PEP and particles functionalized with short organic molecules, we can rule out contributions of permanent adsorption of the chains. DSC showed no change in glass transition temperature. The decrease in the specific heat capacity could be explained by a simple mixing rule. By positron annihilation lifetime spectroscopy, taking properly into account contributions of the silica particles, we rule out an influence of the geometrical confinement on the free volume in the PEP nanocomposites studied here.