Polyquaternium-7

Zhan, Zi-Ming, et al. Industrial & Engineering Chemistry Research 60.39 (2021): 14297-14306.

Polyquaternium-7 (PQ7), a cationic copolymer of dimethyl diallyl ammonium chloride and acrylamide, was applied as a surface modifier to fabricate high-performance polyamide nanofiltration (NF) membranes. The membranes were prepared via interfacial polymerization (IP) on polyethersulfone (PES) substrates. Initially, PES substrates were soaked in deionized water for 12 h and fixed in Teflon molds. The aqueous phase containing 1 wt% piperazine (PIP) was poured onto the substrate for 3 min. Excess solution was removed, and the residual water was eliminated using an air knife. Subsequently, 0.15 wt% trimesoyl chloride (TMC) in hexane was applied for 15 s to form the nascent polyamide layer.

For PQ7-modified membranes, the nascent polyamide layer was immediately heat-cured in 0.5 wt% PQ7 solution at 50 °C for 5 min, facilitating surface grafting of quaternary ammonium groups. Control membranes were cured in water under the same conditions. Following curing, all membranes were washed and stored in deionized water at 4 °C before characterization.

The grafting process enhanced membrane hydrophilicity, surface roughness, and positive charge without altering thickness. Functional evaluation showed increased water flux from 47.8 to 79.6 L m⁻² h⁻¹ under 5 bar and improved divalent ion rejection. Antifouling tests using sodium alginate and bovine serum albumin demonstrated superior flux recovery for PQ7-grafted membranes.

This procedure illustrates a simple and cost-effective method to prepare high-performance NF membranes via surface modification using polyquaternium-7, combining improved permeability, ion selectivity, and fouling resistance.

Samsudin, Asep Muhamad, et al. Journal of Membrane Science and Research 10.3 (2024): e713961.

Polyquaternium-7 (PQ7), a water-soluble cationic polymer, was utilized as a functional additive in the fabrication of quaternary ammonium poly(vinyl alcohol) (QPVA)-based anion exchange membranes (AEMs) for application in anion exchange membrane fuel cells (AEMFCs). The study aimed to optimize AEM performance by modulating the QPVA/PQ7 mass ratio and evaluating the resulting structural and electrochemical properties.

For membrane preparation, a 10 wt% QPVA solution was first dissolved in distilled water at 80 °C with continuous stirring overnight to achieve homogeneity. Separately, PQ7 was diluted to 5 wt% using distilled water. The two solutions were blended at ambient temperature for 4 h in varying mass ratios (QPVA:PQ7 from 1:0.1 to 1:0.5). The resulting polymer blends were cast and crosslinked to form freestanding AEMs.

Comprehensive characterization demonstrated that incorporation of PQ7 enhanced membrane performance. The optimal QPVA/PQ7 ratio of 1:0.5 (denoted QPPQ0.5) exhibited the highest hydroxide conductivity of 45.63 mS cm⁻¹ at 80 °C, alongside high tensile strength ranging from 33.29 to 48.55 MPa. PQ7 contributed to increased water uptake and controlled swelling, while maintaining mechanical integrity and enabling efficient ion transport.

These results underscore the critical role of polyquaternium-7 in improving the structural, thermal, and electrochemical properties of AEMs. PQ7 serves as a cost-effective, facile, and functional polymer additive for the preparation of high-performance AEMs, demonstrating significant potential for next-generation fuel cell technologies.

Samsudin, A. M., Abdullah, A., Nasher, K., & Kamal, M. T. (2024). In E3S Web of Conferences (Vol. 503, p. 08006). EDP Sciences.

Polyquaternium-7 (PQ7), a cationic water-soluble polymer, was employed as a functional copolymer to enhance hydroxide conduction in poly(vinyl alcohol) (PVA)-based anion exchange membranes (AEMs) for alkaline polymer electrolyte fuel cells. PQ7 provides quaternary ammonium groups that serve as hydroxide-conducting sites, while thermal and chemical crosslinking mitigates excessive swelling and maintains membrane integrity.

For membrane fabrication, a 10 wt% PVA solution was prepared by dissolving PVA in distilled water at 80 °C with continuous overnight stirring. Separately, a 5 wt% PQ7 solution was obtained by diluting a 10 wt% stock solution. The PVA and PQ7 solutions were blended at ambient temperature for 4 h in varying mass ratios. The resulting mixtures were cast and crosslinked to yield freestanding membranes.

Characterization by FTIR confirmed the presence of functional groups corresponding to PVA, PQ7, and crosslinking linkages, while SEM images indicated smooth, uniform membrane morphologies. Increasing PQ7 content enhanced water uptake and swelling degree, reflecting improved hydrophilicity. Ion exchange capacity (IEC) analysis revealed a direct correlation between PQ7 content and hydroxide-conducting functionality, reaching a maximum IEC of 1.52 mmol g⁻¹ at a PQ7/PVA ratio of 0.5. Correspondingly, hydroxide conductivity attained 9.26 mS cm⁻¹ at room temperature, demonstrating effective facilitation of hydroxide ion transport.

These results highlight the critical role of polyquaternium-7 in the preparation of high-performance AEMs, providing a facile and cost-effective strategy to engineer membranes with enhanced ionic conductivity, controlled swelling, and structural stability for fuel cell applications.