Thermo-responsive and antifouling PVDF nanocomposited membranes based on PNIPAAm modified TiO2 nanoparticles

A novel hydrophilic nanocomposite additive (TiO₂-g-PNIPAAm) was synthesized by the surface modification of titanium dioxide (TiO₂) with N-isopropylacrylamide (NIPAAm) via “graft-from” technique. And the nanocomposite membrane of poly(vinylidene fluoride) (PVDF)/TiO₂-g-PNIPAAm was fabricated by wet phase inversion. The graft degree was obtained by thermo-gravimetric analysis (TGA). Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) characterization results suggested that TiO₂-g-PNIPAAm nanoparticles segregated on membrane surface during the phase separation process. Scanning electron microscopy (SEM) was conducted to investigate the surface and cross-section of the modified membranes. The water contact angle measurements confirmed that TiO₂-g-PNIPAAm nanoparticles endowed PVDF membranes better hydrophlilicity and thermo-responsive properties compared with those of the pristine PVDF membrane. The water contact angle decreased from 92.8° of the PVDF membrane to 61.2° of the nanocompostie membrane. Bovine serum albumin (BSA) static and dynamic adsorption experiments suggested that excellent antifouling properties of membranes was acquired after adding TiO₂-g-PNIPAAm. The maximum BSA adsorption at 40 °C was about 3 times than that at 23 °C. The permeation experiments indicated the water flux recover ratio and BSA rejection ratio were improved at different temperatures.