Visualizing and quantifying the nanoscale hydrophobicity and chemical distribution of surface modified polyethersulfone (PES) membranes

Abstract

Chemical modifications bring unique properties into polymeric membranes that may have enhanced filtration or separation efficiencies, antifouling, antimicrobial activity and selectivity. However, there is a lack of nanoscale characterization of the chemical additive distribution and the impacts of chemical modifiers or additives on membrane surface properties, especially those at the nanoscale. In this study, a series of industrially relevant polyethersulfone (PES) membranes modified with poly (ethylene glycol) (PEG) and polyvinylpyrrolidone (PVP) were analysed systematically. Particularly, hydrophobicity and chemical distribution were scrutinized by atomic force microscopy (AFM) and AFM coupled with infrared analysis capability (AFM-IR) for the first time that successfully resolved nanoscale structural and chemical properties of the chemically modified PES membranes. Our results indicated the heterogeneous spatial distribution of PVP and PEG based on their characteristic IR bands and the resulting hydrophobicity distribution on modified membrane surfaces at the nanoscale. Particularly, we established a linear correlation (R = 0.9449) between the measured adhesion force and water contact angles, which enabled the examination of local surface hydrophobicity. The PES membranes became more hydrophilic with the increasing blend of PVP and PEG. With AFM-IR, trace amounts (1-4%) of PVP could be identified sensitively on PES membranes based on their unique characteristic IR bands, which were not achieved by FTIR or IR mapping. Overall, these novel characterization approaches hold paramount importance for the design and quality control of polymer membrane modification and manufacturing.

Fabrication, characterization, and performance evaluation of polyethersulfone/TiO2 nanocomposite ultrafiltration membranes for produced water treatment

“…The aromatic bonds appeared at around 1486 and 1578 cm −1 . The reported peaks are in good agreement with literature . The incorporation of TiO 2 nanoparticles into the polymer matrix exhibited no noticeable shift in spectra and intensity of peaks indicating the formation of no bonds in between the functional groups of polymer and TiO 2 .…”

Improving Immunoassay Performance with Cleavable Blocking of Microarrays

“…Contact angle measurements were used for macroscopic characterization, as described in the Supporting Information. The nanoscale uniformity of the fluorous coating was studied by measuring the adhesion force of the hydrophobic AFM cantilever, as recently reported . The more hydrophobic the surface, the greater the adhesion force.…”

“…The nanoscale uniformity of the fluorous coating was studied by measuring the adhesion force of the hydrophobic AFM cantilever, as recently reported. 39 The more hydrophobic the surface, the greater the adhesion force. In the background zone of the microarray, most of the surface showed relatively strong adhesion to the hydrophobic cantilever (Figure S3A).…”

Bioinspired Edible Lubricant-Infused Surface with Liquid Residue Reduction Properties

“…Edible superhydrophobic surfaces with self-cleaning ability were brought up to provide residue reduction [9][10][11][12]. Superhydrophobic surfaces inspired by nature's lotus plant leaf have huge potentials in the fields of anti-icing [13], antifouling [14], antifogging [15,16], and antifrosting [17,18]. Traditionally perfluorinated compounds (PFCs) and their derivatives were applied for the fabrication of superhydrophobic surfaces; however, those chemicals are potentially harmful to mammals and the environment [19][20][21].…”