Sorption of gases and liquids by polymers of intrinsic microporosity (PIMs)

摘要

This study presents the synthesis of polymers of intrinsic microporosity and the investigation of their microporosity using gas sorption and adsorption of liquids and vapours. Microporous polymeric materials PIM-1, TAPIM-1, PIM-2 and PIM-7 were synthesised using step-growth polymerisation. The microporosity of these materials was studied using gas sorption and adsorption of molecules in the liquid phase. A procedure to validate gas sorption methods was undertaken before being used to characterise microporous materials. The sorption methodology was validated using standard reference materials (SRMs) and collaborative testing, and the PSD evaluation was validated using a well defined crystalline material. Different approaches to obtaining pore size distribution (PSD) data were dealt with. Gas sorption methods that use CO2 at 273 K and at 303 K, N2 at 77 K, H2 at77 K, and Xe (298 K) to determine PSD were compared. The Horvath-Kawazoe(HK) model was presented as the preferred model and the N2, CO2 and H2 sorption data were treated under this approach. CO2 PSD data at 273 K and at303 K was compared against N2 PSD data and a novel complementary relationship established. PIM-1 samples in film form and powder form were used to investigate the effect of sample form on the sorption properties of the material. PIM-1, PIM-2, TAPIM-1, ethano-anthracene PIM-1 copolymers, and triptycene based PIMs were used to investigate the influence of polymer structure on gas sorption properties. The free volume properties of a PIM-1 ethano-anthracene copolymer (PIM-CO1-40), was compared against PIM-1. A number of independent techniques, namely N2 sorption, Xe sorption, Positron annihilation lifetime spectroscopy (PALS), and 129Xe NMR were used to probe the free volume. The time dependence of free volume and its bearing on diffusivity of PIM-1 membranes was investigated. Water, chloroform and simple alcohols were used to investigate adsorption in the liquid and vapour phases. Interaction with PIM-1 the aromatic ether linkage and the nitrile group produced frequency shifts in ATR-FT-IR spectra. These frequency shifts were used to compare relative strengths of the hydrogen bonds.