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).