Partial crosslinking method for poly(2,6-dimethyl-1,4-phenylene oxide)-poly(vinyl alcohol) membranes to obtain optimized stability and permeability

A partial crosslinking method was developed to modify hydrophilic membranes. The membrane was sandwiched between two porous plates to protect part of the areas, then immersed into a crosslinking solution such as glutaraldehyde, and finally, set free from the plates. The protected and unprotected areas were alternatively distributed to form a heterogeneous membrane. The unprotected areas were crosslinked to enhance the membrane stability, whereas the protected areas retained their original permeability. Three types of hydrophilic base membranes were selected and prepared from poly(2,6-dimethyl-1,4-phenylene oxide) and poly(vinyl alcohol). The base membranes were partially crosslinked (5.56% of the direct area with enlarged areas) to investigate their stability and diffusion dialysis (DD) performances. The partially crosslinked membranes had remarkably reduced water uptake and swelling degrees compared with the base membranes (72.4%-250.4% vs. 178.2%-544.4% and 94.0%-408.0% vs. 163.8%-814.8%). Meanwhile, the membranes still retained high DD performances for separating HCl-FeCl2 or NaOH-NaAlO2 solutions. The dialysis coefficients of HCl and NaOH were much higher than those of the fully crosslinked membranes (0.0209 vs. 0.0109 m/h and 0.0059-0.0085 vs. 0.0017-0.0022 m/h). Hence, partial crosslinking was effective in optimizing the membrane hydrophilicity and permeability. (C) 2017 Wiley Periodicals, Inc.