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

In this work, poly(4-methyl-2-pentyne) (PMP) with quaternary ammonium salts has been functionalized in order to increase CO₂ selectivity. Functional groups have been introduced by a two-stage method: (i) bromination of the initial polymer and (ii) addition of tertiary alkylamines, namely 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 PMP functionalization. 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 have been 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.