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Effect of polymer molecular weight on the long-term process stability of crosslinked polybenzimidazole organic solvent nanofiltration (OSN) membranes.

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Title: Effect of polymer molecular weight on the long-term process stability of crosslinked polybenzimidazole organic solvent nanofiltration (OSN) membranes.
Authors: Oxley, Adam1,2 (AUTHOR), Livingston, Andrew G.1,2 (AUTHOR) a.livingston@qmul.ac.uk
Source: Journal of Membrane Science. Jan2024, Vol. 689, pN.PAG-N.PAG. 1p.
Subjects: Molecular weights, Crosslinked polymers, Polymers, Organic solvents, Nanofiltration, Compacting
Abstract: The importance of polymer molecular weight on the long-term performance of polybenzimidazole (PBI) membranes in organic solvents was investigated. PBI membranes were manufactured from two different polymer molecular weights: the standard molecular weight of PBI polymer, used almost universally across literature for organic solvent stable membranes (∼27,000 g mol-1), and an untested ∼ two-fold higher molecular weight (∼60,000 g mol-1). After crosslinking, all PBI membranes were chemically and mechanically stable. However, during continuous long-term pressurised filtration in DMF, the standard molecular weight PBI membranes suffered slow permeance decline over time. This was attributed to rearrangement of the crosslinked polymer chains. Increasing the extent of crosslinking reduced the rate of membrane permeance decline but did not provide a fully process stable membrane. Using a higher molecular weight PBI, and a similar extent of crosslinking, resulted in a membrane with constant permeance and excellent process stability, even during continuous DMF filtration at 120 °C. This was attributed to the increased interchain interactions and entanglement in the high molecular weight polymer, which reduced the rate of chain rearrangement and compaction. This work demonstrates the importance of polymer molecular weight for reducing membrane compaction and providing process stability in organic solvents. [Display omitted] • Membranes were cast from a standard molecular weight (MW) PBI and a high MW PBI. • These membranes were crosslinked with dibromo-p-xylene to different crosslinking extents. • The PBI MW was critically important to the long-term membrane stability. • Only PBI with a high MW and a high crosslinking extent gave membranes stable in DMF. • The standard MW PBI with the same crosslinking extent suffered significant permeance loss. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:The importance of polymer molecular weight on the long-term performance of polybenzimidazole (PBI) membranes in organic solvents was investigated. PBI membranes were manufactured from two different polymer molecular weights: the standard molecular weight of PBI polymer, used almost universally across literature for organic solvent stable membranes (∼27,000 g mol-1), and an untested ∼ two-fold higher molecular weight (∼60,000 g mol-1). After crosslinking, all PBI membranes were chemically and mechanically stable. However, during continuous long-term pressurised filtration in DMF, the standard molecular weight PBI membranes suffered slow permeance decline over time. This was attributed to rearrangement of the crosslinked polymer chains. Increasing the extent of crosslinking reduced the rate of membrane permeance decline but did not provide a fully process stable membrane. Using a higher molecular weight PBI, and a similar extent of crosslinking, resulted in a membrane with constant permeance and excellent process stability, even during continuous DMF filtration at 120 °C. This was attributed to the increased interchain interactions and entanglement in the high molecular weight polymer, which reduced the rate of chain rearrangement and compaction. This work demonstrates the importance of polymer molecular weight for reducing membrane compaction and providing process stability in organic solvents. [Display omitted] • Membranes were cast from a standard molecular weight (MW) PBI and a high MW PBI. • These membranes were crosslinked with dibromo-p-xylene to different crosslinking extents. • The PBI MW was critically important to the long-term membrane stability. • Only PBI with a high MW and a high crosslinking extent gave membranes stable in DMF. • The standard MW PBI with the same crosslinking extent suffered significant permeance loss. [ABSTRACT FROM AUTHOR]
ISSN:03767388
DOI:10.1016/j.memsci.2023.122149