Gas sorption in polymers with intrinsic microporosity

Introduction High free volume polymers exhibit promising properties for gas/gas, gas/vapour and vapour/vapour separations where high fluxes are required. Such polymers have an intermediate structure between that of "classical" porous and non-porous materials. Their transport properties differ dramatically, depending on the specific chemical structure of the polymer and the penetrant. In comparison with other polymers, polymers with intrinsic microporosity (PIMs) due to their intrinsic structure exhibit interesting properties (Fig. 1) which can be used for instance for CO2 capturing or for targeted membrane separation processes [2]. Figure 1. The correlation of sorption (left) and diffusion (right) coefficients with a square of critical temperature or critical volume, respectively of gases and vapours in PIM-1. Correlation of polysufone (PSF) and polydimethylsiloxane (PDMS) diffusion data with critical volume were taken from [3]. Experimental In this work, the sorption of gases (CO2, N2, O2, CH4 a C4H10) in several samples (flat membrane/powder) based on polymers with intrinsic microporosity (PIM) and in PIM-1 with various concentrations of porous nanofiller ZIF-8 in polymer matrix[4] is presented. Sorption experiments were performed gravimetrically at 25?C, using home-made sorption apparatuses equipped with McBain's spiral balances and with an automatic charge-coupled device camera system detection of sample-target-point position [5]. Such system enables to follow the sorption kinetics of appropriate sorbent in a given polymer and enables to evaluate both sorption and diffusion coefficient from recorded sorption data. Results and Conclusions Figure 2. CO2 sorption isotherms in studied samples at 25?C. PIMs show a surprisingly high solubility of permanent gases such as carbon dioxide in comparison with other polymers. This is related to their microporous nature and their particularly high BET surface area. It can be seen that gas sorption in PIMs can be described by the well-known dual mode model (Fig. 2). Ethanol-treated PIM-1 with 43.1 vol.% of nanoZIF-8 filler showed the highest CO2 sorption at pressures over 5 bar. Acknowledgement The work leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° NMP3-SL-2009-228631, project DoubleNanoMem. The authors are also thankful for financial support of the Grant Agency of Czech Republic (Grant No. 106/10/1194). References [1]P.M. Budd, B.S. Ghanem, S. Makhseed, N.B. McKeown, K.J. Msayib, C.E. Tattershall, Polymers of intrinsic microporosity (PIMs): robust, solution-processable, organic nanoporous materials, Chem. Commun. (2004) 230-231. [2]P.M. Budd, N. B. McKeown, B.S. Ghanem, K.J. Msayib, D. Fritsch, L. Staranikova, N. Belov, O. Sanfirova, Yu. Yampolskii, V. Shantarovich, Gas permeation parameters and other physicochemical properties of a polymer of intrinsic microporosity: Polybenzodioxane PIM-1, J. Membr. Sci. 325 (2008) 851-860. [3]S. Matteucci, Y. Yampolskii, B. Freeman, I. Pinnau, Transport of gases and vapors in glassy and rubbery polymers, Chapter 1, 1-48 in Yu. Yampolskii, I. Pinnau, B.D. Freeman (Eds.), Materials Science of Membranes for Gas and Vapor Separation, John Wiley & Sons, Chichester, England, 2006. [4]A.F. Bushell, M.P. Attfield, C.R. Mason, P.M. Budd, Y. Yampolskii, L. Starannikova, A. Rebrov, F.Bazzarelli, P. Bernardo, J.C. Jansen, M. Lan?, K. Friess, Gas permeation parameters of mixed matrix membranes based on the polymer of intrinsic microporosity PIM-1 and the zeolitic imidazolate framework ZIF-8, J. Membr. Sci. (2011), submitted. [5] K. Friess, J.C. Jansen, O. Vopi?ka, A. Randová, V. Hynek, M. ?ípek, L. Bartovská, P. Izák, M. Dingemans, J. Dewulf,