Cross-linking of brominated poly(1-trimethylsilyl-1-propyne) using polyethylenimine as a cross-linking agent

In this work cross-linked polymer membranes were obtained by heat treatment of films prepared from a solution containing a mixture of brominated poly(1-trimethylsilyl-1-propyne) [PTMSP] and polyfunctional amine polyethylenimine [PEI] as a cross-linking agent. The cross-linked products were identified on the basis of IR spectra, elemental analysis data, and the stability of the reaction products to the solvent (CCl4) in which the original brominated PTMSP is soluble. According to the IR spectra, the crosslinking reaction occurs via the reactive C-Br bond in bromine-containing PTMSP with the participation of PEI amino groups at temperatures above 90°C. Cross-linking of bromine-containing PTMSP makes it resistant to organic solvents. An increase of PEI-content in the mixture correlates with an increase in the proportion of bromine atoms that have reacted. The cross-linked polymer transport parameters were studied for individual gases and in a methane/n-butane mixture (98.4 mol.% methane and 1.6 mol.% n-butane). In the series PTMSP – brominated PTMSP-Br – PTMSP-Br/PEI (before cross-linking) – PTMSP-Br/PEI (after cross-linking) the permeability to individual gases decreases. Cross-linked PTMSP in a methane/n-butane mixture demonstrates high permeability coefficients of n-butane (P n-C4H10 = 12000 Barrer) and selectivity for the release of n-butane from a mixture with methane (α n-C4H10/CH4 = 13).