Interaction of a Polymer of Intrinsic Microporosity (PIM-1) with Penetrants

Abstract

The characterisation, solubility testing, and alcohol adsorption studies of PIM-1 are reported. Techniques used for characterisation are N2 sorption and ATR-FTIR analysis. A number of solvents were tested for their ability to dissolve low molecular weight (~30 000 gmol-1), medium molecular weight (~60 000 gmol-1), and high molecular weight (~120 000 gmol-1) PIM-1.Results showed solubility of PIM-1 in these solvents to be dependent on molar mass. CHCl3, tetrahydrofuran (THF), CH2Cl2, dicholobenzene (DCB), 1,2,4- trichlorobenzene (TCB), and acetophenone were found to be good solvents at all molecular weights. Treatment of PIM-1 with nonsolvents, namely: small alcohols and water, followed by solvent removal, caused swelling, resulting in an increase in BET surface area of about 11 %, except for water, which reduced BET surface area by the same amount (11 %). Methanol (MeOH) treatment resulted in a new population of micropores around 0.6 nm. The change after ethanol (EtOH) and propanol (PrOH) treatment was not as significant. Hydrogen bonding between alcohols and PIM-1 was also investigated using shifts in the frequencies of FTIR peaks for the ether and the nitrile functional groups. Nitrile group frequencies for the alcohols were consistently blue-shifted, whereas the ether frequencies were red shifted. Both red- and blue-shifts were used as a measure of hydrogen bond strength.