Functionalizing a Polyelectrolyte Complex with Chitosan Derivatives to Tailor Membrane Surface Properties

Abstract

Polyelectrolyte complex (PEC) materials show promise in the development of tunable membranes for aqueous and organic solvent separations, as well as in the creation of surface layers for fouling control. In this study, we developed a polyelectrolyte complex (PEC) functionalized by negatively charged carboxymethyl chitosan (CMC−) and positively charged quaternized chitosan (QC+) to tailor its surface properties and antibacterial efficacy. CMC− and QC+ were prepared and characterized using FT-IR and 1 H NMR, which confirmed the presence of the carboxymethyl group and trimethylammonium group in CMC− and QC+ with 65.6% and 83.9% substitution, respectively. The CMC− functionalized PEC (CMC−/PEC) and QC+ functionalized PEC materials (QC+/PEC) were evaluated for their stability in water, resistance to organic and inorganic adsorption, and antibacterial action against a model microorganism, Pseudomonas putida. The results showed no release of chitosan derivatives after adsorption, and CMC−/PEC and QC+/PEC exhibited charge-based, selective repulsion of model organic and inorganic substances. Moreover, the functionalized PEC surfaces displayed lower bacterial attachment due to their smoother surfaces as compared to the bare ceramic membrane and their antimicrobial properties. Among the PEC samples, CMC−/PEC had the lowest cell attachment, while QC+/PEC showed the highest attachment due to electrostatic attraction. The ceramic and bare PEC surfaces were negligibly bactericidal, while cell viability decreased to 34.4 ± 10.2% and 30.6 ± 8.2% with the CMC−/PEC and QC+/PEC surfaces, respectively. In the filtration experiments, the unmodified PEC and CMC−/PEC showed lower rates of flux decline due to organic fouling than did the bare ceramic or QC+/PEC due to electrostatic repulsion. Furthermore, PECs as protective layers promoted much higher flux recoveries than simply backwashing the uncoated membranes. This surface tunability, then, enhances the potential of PECs either as fouling resistant materials or as a method to create a sacrificial, protective layer on surfaces that once fouled can be dissolved and reestablished.

Influence of divalent ions on composition and viscoelasticity of polyelectrolyte complexes

“…Polyelectrolyte complexes (PECs) are electrostatically selfassembled soft materials that are finding increasing utility in diverse domains as underwater adhesives, [1][2][3][4][5][6] encapsulants and drug delivery agents, [7][8][9][10][11] membrane-less protocell models, 12,13 water purification agents, 14 membranes for separation processes, [15][16][17] and barrier films for packaging. 18,19 In many of these applications, PECs are exposed to monovalent (e.g., K + , Na + , Cl À ) and multivalent ions (e.g., Ca 2+ , SO 4 2À , Fe 3+ in biological systems, Mg 2+ in wastewater, PO 4 3À in buffers).…”

Self-Assembled CMC/UiO-66-NH2 Membrane with Anti-Crude Oil Adhesion Property for Highly Efficient Oil–Water Separation

“…24 Therefore, CMC is considered to be a candidate to design membrane materials with outstanding anti-fouling performance. 25 Combined with previous studies, achieving outstanding surface wettability not only depends on the hydrophilic components on the membrane surface but also depends on the rough structures of the membrane surface. As a metal−organic framework (MOF) material with hydrophilic Zr 6 O 4 (OH) 4 (zirconium metal cluster subunit) as a node and 2-aminoterephthalic acid as a linker, UiO-66-NH 2 possesses the strong hydration ability to further form the robust hydration layer, which is applicable for enhancing the anti-fouling property of the membrane.…”

“…Zhang et al fabricated a composite membrane by coating cellulose–starch–silica (CSS) on a nylon membrane; the prepared membrane showed superior selective wetting characteristics for oil and water because of the plentiful hydrophilic component and micro-nanoconstruction . Therefore, CMC is considered to be a candidate to design membrane materials with outstanding anti-fouling performance . Combined with previous studies, achieving outstanding surface wettability not only depends on the hydrophilic components on the membrane surface but also depends on the rough structures of the membrane surface.…”

The key to maximizing the benefits of antimicrobial and self-cleaning coatings is to fully determine their risks

“… Contact killing : After direct contact, inhibition of microbes is achieved via cell membrane damage, DNA damage, enzyme deactivation and other genotoxicities. Examples include chitosan and other polymeric coatings [ 34 ], nano-silver, nano-TiO 2 [ 35 ] and nano-copper/copper oxide. Anti-adhesion : The surface topography and wettability are modified to repel microbe attachments and further inhibit the formation of biofilms.…”

“…Contact killing : After direct contact, inhibition of microbes is achieved via cell membrane damage, DNA damage, enzyme deactivation and other genotoxicities. Examples include chitosan and other polymeric coatings [ 34 ], nano-silver, nano-TiO 2 [ 35 ] and nano-copper/copper oxide.…”