Structure and properties of poly(4-methyl-2-pentyne) synthesized with NbBr5 and TaBr5-based catalytic systems

Abstract In this work, we used the concept of controlling the properties of poly(4-methyl-2-pentyne) [PMP] by changing the polymerization conditions. We synthesized PMP using novel NbBr5-and TaBr5-based catalytic systems. PMP obtained with TaBr5-based systems are characterized not only by greater resistance to dissolution, but also by significantly more limited swelling in organic solvents compared to PMP obtained with NbBr5-based catalysts. Solution and solid-state 13C NMR spectroscopy showed that synthesized PMP samples have a mixed ratio of cis-/trans-units. The X-ray diffraction indicated an increase in the polymer packing density with an increase in the dissolution selectivity, which can be associated not only with the ratio of cis-/trans-units in polymers, but also with the lengths of the sequences of units of the same geometry that influences the polymer conformation. According to the low-temperature argon sorption PMP demonstrates high Brunauer–Emmett–Teller (BET) surface area (up to 846 cm3/g). PMP film membranes exhibit a high level of permeability (PO2 = 1400–2100 barrer for polymers synthesized with NbBr5-based catalysts and PO2 ∼ 1100 barrer for polymers synthesized with TaBr5-based catalysts). This study provides the opportunity of obtaining PMP, combining high permeability with high resistance to organic substances.