Dry–wet spinning of temperature-sensitive PVDF hollow-fiber membranes at different bore fluid flow rates

In this work, dry–wet spinning was conducted to fabricate poly(vinylidene fluoride)-g-poly(N-isopropylacrylamide) (PVDF-g-PNIPAAm) copolymer hollow-fiber membranes. The effect of the bore fluid flow rate (BFFR) on the structure and performance of each hollow-fiber membrane was investigated by X-ray photoelectron spectroscopy (XPS), field emission scan electronic microscopy (FESEM), pore-size measurements, mechanical property evaluations, and a filtration experiment. It was found that the grafted PNIPAAm chains aggregated on the inner surface of the fiber membrane due to the effect of the bore fluid. When the permeation temperature was increased from 20 to 45 °C, a drastic reduction in the pure-water flux and a remarkable increase in the retention of bovine serum albumin (BSA) were observed at around 32 °C, indicating that the as-prepared fiber membranes exhibit excellent temperature sensitivity. Pore-size measurements confirmed that both the mean pore size and the porosity increase with increasing BFFR, endowing the fiber membranes with high pure-water fluxes and low retentions of BSA.