How Much Do Ultrathin Polymers with Intrinsic Microporosity Swell in Liquids?

Wojciech Ogieglo, Bader Ghanem, Xiaohua Ma, Ingo Pinnau, Matthias Wessling

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

As synthetic membrane materials, polymers with intrinsic microporosity (PIMs) have demonstrated unprecedented permeation and molecular-separation properties. Here, we report the swelling characteristics of submicron-thick supported films of spirobisindane-based PIMs, PIM-1 and PIM-6FDA-OH, for six organic solvents and water using in situ spectroscopic ellipsometry. Surprisingly, PIMs swell significantly in most organic solvents, with swelling factors (SF = h/h) as high as 2.5. This leads to the loss of the ultrarigid character of the polymer and produces equilibrated liquid-like swollen films. Filling of the excess frozen-in fractional free volume with liquid was discovered next to swelling-induced polymer matrix dilation. Water hardly swells the polymer matrix, but it penetrates into the intrinsic microporous structure. This study is the first to provide fundamental swelling data for PIMs, leading to better comprehension of their permeation properties. Such an understanding is indispensable for applications such as solvent filtration, natural-gas separation, and ion retention in flow batteries.
Original languageEnglish (US)
Pages (from-to)10403-10410
Number of pages8
JournalThe Journal of Physical Chemistry B
Volume120
Issue number39
DOIs
StatePublished - Sep 27 2016

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