PVDF-g-PNIPAAm Copolymerization Temperature Sensitive Membrane Performance Optimization

The smart membrane is developed based on biomimetic materials,which has important applications in the areas of biochemical purification,drug controlled release,water treatment and other fields.The smart membrane contains a polymer capable of sensing and responding to the external environment,then the membrane pore size,flux and permeability can be changed.This kind of membrane has both excellent performance of substrate membrane and stimulative responsibility of environment,which has aroused people's interest in recent years.In this paper,we hope to prepare a thermo-sensitive membrane with good temperature sensitivity and hydrophilicity.In this study,a temperature-sensitive copolymer of PVDF-g-PNIPAAm was synthesized by free-radical polymerization.And then PVDF and PVDF-g-PNIPAAm thermo-sensitive membranes were prepared by immerged phase-inversion process.The properties and structures of PVDF-g-PNIPAAm membranes prepared by changing solvent and coagulation bath compositionand post-treatment with ethanol were studied by water contact angle,scanning electron microscope(SEM),X-ray photoelectron specroscopy(XPS)and flux of pure water.The results show that the membrane structure and permeability can be affected by regulation of PVDF-g-PNIPAAm membrane preparation process.When the THF in the casting solution,the NIPAAm content of the membrane surface increases as the standing time increases,meanwhile the hydrophilicity of the membrane surface increases.With the increase of standing time,the membrane surface pore size and the number of finger pores increase as well,resulting the pure water flux increases,and the water flux with temperature changes.When the NaCl content in the coagulation bath increases,the activity of the water is decreases,therefore reduces the exchange rate of the solvent and non-solvent,resulting in form a more dense membrane structure.The higher content of NaCl in the coagulation bath,the higher of the breaking strength,rejection and the hydrophilicity of membrane are..After swelled in ethanol,the membrane hydrophilicity,mechanical properties,temperature sensitivity have a certain improvement.If the ethanol treatment time is longer than 3 days,the degree of swelling becomes larger,making the temrmo-sensitive membrane structure damaged,and membrane temperature sensitivity,hydrophilicity,mechanical properties decreases.