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

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), 1,2,4trichlorobenzene (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 redand blue-shifts were used as a measure of hydrogen bond strength.