Influence of Poly(ethylene glycol) Segment Length on CO 2 Permeation and Stability of PolyActive Membranes and Their Nanocomposites with PEG POSS Md. Mushfequr Rahman, † Volkan Filiz,* ,† Sergey Shishatskiy, † Clarissa Abetz, † Prokopios Georgopanos, † Muntazim Munir Khan, † Silvio Neumann, † and Volker Abetz* ,†,‡ † Helmholtz-Zentrum Geesthacht, Institute of Polymer Research, Max-Planck-Straße 1, 21502 Geesthacht, Germany ‡ Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, 20146 Hamburg, Germany * S Supporting Information ABSTRACT: Three grades of PolyActive block copolymers are investigated for CO 2 separation from light gases. The polymers are composed of 23 wt % poly(butylene terephthalate) (PBT) and 77 wt % poly(ethylene glycol terephthalate) (PEGT) having the poly(ethylene glycol) segments of 1500, 3000, and 4000 g/mol, respectively. A commercial PEG POSS (poly(ethylene glycol) functionalized polyoctahedral oligomeric silsesquioxanes) is used as a nanofiller for these polymers to prepare nanocomposites via a solvent casting method. Single gas permeabilities of N 2 ,H 2 , CH 4 , and CO 2 are measured via the time-lag method in the temperature range from 30 to 70 °C. The thermal transitions of the prepared membranes are studied by differential scanning calorimetry (DSC). It is found that the length of PEG segment has a pronounced influence on the thermal transition of the polymers that regulates the gas separation performance of the membranes. The stability of the nanocomposites is also correlated with the thermal transition of the polyether blocks of the polymer matrices. KEYWORDS: PolyActive, PEG POSS, gas separation membrane, nanocomposite, mixed-matrix membrane 1. INTRODUCTION Fast and selective transport of the gas molecules through polymers has brought the membrane separation technology to the advent of a new era, leading eventually to the wide use of an energy saving and environmentally friendly gas separation process. Polymeric membranes have so far been the most attractive choice in at least 90% of the installed membrane based gas separation plants. At present, only a very few polymer materials are used to fabricate industrial membranes, although several hundreds of polymers have been reported for their gas separation properties. 1 From an application point of view the most basic requirements of a membrane material is to have a high gas permeation rate maintaining the desired selectivity. An increase of permeance reduces the membrane area required for a desired separation which results in reduced footprint and investment costs. Nonetheless, the material selection criterion also involves durability (e.g., mechanical integrity) at the operating conditions. A balance between these features to maintain high separation efficiency makes the task of material selection quite difficult. Therefore, the search for robust materials with better separation performance at the operating conditions is still going on. 2-6 This endeavor led the researchers to thoroughly examine the chemical and physical properties of the polymers which are essential to separate a particular gas mixture. In recent years, the quest has proceeded from the qualitative analysis of data to the development of quantitative models with predictive abilities facilitating directed search for advanced membrane materials. 7 CO 2 removal occupies the central position among all the current gas separation membrane applications because of the increasing emphasis on global warming mitigation. At present fossil fuel accounts for 80% of the global energy needs which causes enormous amount of CO 2 emission. In spite of the tremendous development of alternative energy production technologies (e.g., solar energy, wind power, biomass energy, etc.) the ever growing energy requirement is expected to depend on fossil fuels at least for the next few decades. 8,9 Among the three major fossil fuel (i.e., coal, gas, and oil) coal constituents about 65% of the fossil fuel reserve and is expected to be the only remaining fossil fuel after 2042. 8 Due to the availability and low cost a large percentage of electricity Special Issue: Forum on Polymeric Nanostructures: Recent Advances toward Applications Received: June 29, 2014 Accepted: September 17, 2014 Forum Article www.acsami.org © XXXX American Chemical Society A dx.doi.org/10.1021/am504223f | ACS Appl. Mater. Interfaces XXXX, XXX, XXX-XXX