Synthesis and Properties of Poly(4-methyl-2-pentyne) Containing Quaternary Ammonium Salts with Methyl and Ethyl Substituents

In this work, functionalization of poly(4-methyl-2-pentyne) (PMP) with quaternary ammonium salts was carried out in order to increase CO₂ selectivity in its membrane recovery. The introduction of functional groups was carried out by a two-stage method – bromination of the initial polymer and addition of tertiary alkylamines trimethylamine (TMA) and trimethylamine (TEA). It has been established that the optimal amount of introduced functional groups, while maintaining the mechanical properties of the polymer, is up to 5 mol. %. The results of organoelemental analysis and IR spectroscopy confirm the functionalization reaction of the PMP. X-ray diffraction patterns of the samples indicate an increase in the interchain distance in the series initial PMP–brominated PMP–functionalized PMP. TGA data confirm high thermal and thermal-oxidative stability. The coefficients of permeability, solubility and diffusion of PMP samples containing TMA and TEA salts were determined for individual gases. An increased ideal selectivity for the separation of gas pairs CO₂/N₂ by 2–3 times and CO₂/CH₄ by 1.5–2 times has been achieved while maintaining the permeability at a high level.