Preparation and characterization of poly(1-trimethylsilyl-1-propyne) cross-linked by aliphatic diamines

The article describes a new method for the preparation of cross-linked poly(1-trimethylsilyl-1-propyne) (PTMSP) using aliphatic diamines. The developed two-stage method includes selective functionalization of the polymer by the bromination reaction of PTMSP and the subsequent use of functional groups in the polymer for cross-linking by the reaction of bromine substitution in the polymer with a diamine. Under the conditions of a polymer solution with added diamines, the effect of the chain length of the diamine, the reaction temperature, and the bromine content in the polymer on the cross-linking efficiency was studied. It was shown that the cross-linking efficiency depends on the length of the diamine chain and on the bromine content in PTMSP. The identification of cross-linked products was carried out on the basis of elemental analysis data, the stability of the reaction product to the solvent (CCl4), in which the starting brominated PTMSP dissolves, and by IR spectroscopy. Cross-linked films of brominated PTMSP resistant to organic solvents were obtained using 1,12-diaminododecane, which showed the highest efficiency in the reaction in solution. The individual gases (H2, N2, O2, CH4, CO2, and n-C4H10) and mixed n-butane/methane permeability of the pure, brominated and cross-linked PTMSP films were measured. The obtained data demonstrated that cross-linking reduces pure gases permeability as well as mixed n-butane and methane permeability of cross-linked PTMSP films in comparison with initial PTMSP. Cross-linked PTMSP film showed that ideal selectivity calculated from pure gas measurements enhanced (for example, ideal selectivity for СO2/N2 increased from 6.2 to 10.1) or stayed nearly constant (ideal selectivity for n-С4H10/CH4 was 3.6–3.9) compared to initial PTMSP. Whereas, in contrast, the mixed n-butane/methane selectivity decreased from 22 (unmodified PTMSP) to 14 (cross-linked PTMSP). The nanoporous structure unmodified, brominated and cross-linked PTMSP films was studied by the method of low-temperature nitrogen sorption. The decrease in gas/vapor permeability correlates with changes in the specific surface area and pore volume in the series: PTMSP - brominated PTMSP – cross-linked PTMSP. The high values of the specific surface area and volume of micropores indicate a highly developed nanoporous structure of the obtained cross-linked polymer, which is promising as a membrane and highly sorbing material. [Display omitted] •PTMSP was cross-linked usi