Effects of the Substrate on Interfacial Polymerization: Tuning the Hydrophobicity via Polyelectrolyte Deposition

Abstract

Interfacial polymerization (IP) has been the key method for the fabrication of the thin film composite (TFC) membranes that are extensively employed in reverse osmosis (RO) and forward osmosis (FO). However, the role of the substrate surface hydrophilicity in the formation of the IP-film remains a controversial issue to be further addressed. This study characterized the IP films formed on a series of polyacrylonitrile (PAN) substrates whose hydrophilicities (from ~38 to ~93 degrees) were varied via different approaches, including the alkaline treatment and the deposition of various polycations. It was revealed that delamination could occur when the IP film was formed on a relatively hydrophilic surface; the integrity of the TFC membranes was substantially improved, owing to the modification of the polyelectrolyte deposition. On the other hand, the characterization indicated that the TFC membrane could have an enhanced efficiency (with a factor of ~2) when the substrate was relatively hydrophilic. It was established that the polyelectrolyte deposition could be exploited to effectively tune the substrate surface hydrophobicity, thereby providing more degrees of freedom for the optimization of the TFC membranes fabrication.

Enhancing the Performance of Reversible Zn Deposition by Ultrathin Polyelectrolyte Coatings

“…This improved kinetics implies that the nucleation and growth processes of Zn metal on the bare-Cu substrate require overcoming a larger activation energy barrier than the Cu-PDDA and the Cu-PEI substrates. 27 The enhanced electrodeposition reversibility of Cu-PDDA remains consistent throughout all successive deposition and stripping cycles as at the 100th cycle (Figure 2b).…”

“…For all the samples, the voltage hysteresis decreased to some extent during the cycling due to stabilization of the electrode–electrolyte interface due to passivation and deactivation of reactive sites on the electrode surface. This improved kinetics implies that the nucleation and growth processes of Zn metal on the bare-Cu substrate require overcoming a larger activation energy barrier than the Cu-PDDA and the Cu-PEI substrates . The enhanced electrodeposition reversibility of Cu-PDDA remains consistent throughout all successive deposition and stripping cycles as at the 100th cycle (Figure b).…”

“…Similar to the bare-Cu foils, stable CE was obtained after 40 cycles showing high values of 98.3%° ± 0.6% (PEI) and 99.5%° ± 5 (PDDA). It is important to emphasize that especially for reversible electrodeposition processes, the averaging of a large number of cells is highly important to avoid misinterpretation and inconsistent analysis due to the variation between different cells . Therefore, each point and its corresponding error bar represent the average of a minimum of four separate measurements conducted with the same coating.…”

Polyelectrolyte complex nanofiltration membranes by surface deposition of polyethylenimine on polyanion supports

“…The results were constant with the findings in Liu et al work, in which three polyelectrolytes (PEI, poly(allyl amine hydrochloride, and poly(dimethyl diallyl ammonium chloride) were applied to treat the alkaline hydrolyzed PAN support. The PEI alkaline hydrolyzed PAN support had much higher contact angle (72°) than the alkaline hydrolyzed PAN support (38°) 36 …”

“…The PEI alkaline hydrolyzed PAN support had much higher contact angle (72 ) than the alkaline hydrolyzed PAN support (38 ). 36 2.2 | Membrane performance…”