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 92.8A degrees of the PVDF membrane to 61.2A degrees 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 A degrees C was about 3 times than that at 23 A degrees C. The permeation experiments indicated the water flux recover ratio and BSA rejection ratio were improved at different temperatures.