XPS and contact angle characterization of surface modified cellulose acetate membranes by mixtures of PMHS/PDMS

A mixture of polymethylhydrosiloxane (PMHS) and polydimethylsiloxnae (PDMS) is used for modifying the surface of reverse osmosis and nanofiltration membranes. The porous substructure made of cellulose acetate (CA) was obtained by a phase separation process from acetone/formamide (2/1 wt/wt) casting solutions. Two polymer concentrations (22 and 25 wt.%) were used with a heat post-treatment temperature (80 °C) in order to produce membranes with pore sizes responding to nanofiltration and reverse osmosis needs. Overcoating the CA substructure with a PMHS–PDMS thin layer gave rise to the composite membranes.Surface characterization with X-ray Photoelectron Spectroscopy (XPS) indicates the success of modifying the CA membrane surface with PMHS–PDMS. Contact angle measurements showed an increase in hydrophilicity of the modified membrane surface. Tensile strength measurements indicate that modification by a mixture of PMHS–PDMS has an insignificant decrease in Young's modulus. The pure water flux measurements reveal that layer modification by PMHS–PDMS show an improvement in water permeability which is in agreement with contact angle results.

► In this work, we prepared CA membranes and coated them by mixtures of PMHS–PDMS. ► The introduction of PDMS enhanced hydrophilic character while PMHS has an hydrophobic character. ► This was confirmed by analysis: XPS, contact angle and pure water permeation.