Study On The Improvement Of Adsorption Performance Of PAN Membrane And PVDF Membrane By Swelling Method

The adsorption property of polymers are widely used in chemical and pharmaceutical fields.Some polymers have unsatisfactory adsorption performance(e.g.,difficulty in adsorption,low adsorption capacity,and unstable adsorption)because of their structure.A solvent-induced swelling modification method was proposed in this paper to solve these problems.The polymers were immersed in the mixed solution of the good solvent and the nonsolvent to enhance the adsorption for small molecules or macromolecule on polymer in the swollen state,respectively.The adsorption of methylene blue(MB)on polyacrylonitrile(PAN)was investigated in the process of adsorption of small molecules.Major parameters involved in the modification process(including swelling temperature and concentration of good solvent)on the adsorption performance were analyzed.The results showed that the swelling could reduce the crystallinity and Tg of the polymer,indicating that the mobility of polymer chain segments and free volume increased,which could provide more adsorption sites and facilitate adsorption.The adsorption experiments showed that the swelling modification could increase the adsorption capacity of MB on PAN by 640%under the same temperature conditions and the adsorption capacity of polymers increased with an increase in the good solvent concentration and temperature.However,the solvent concentration and temperature will have a critical value.The swelling degree of the polymer will be too large if the critical value is exceeded,which will damage the polymer matrix and reduce the tensile strength.For this reason,it is important to grasp the degree of swelling.The adsorption of PEO-PPO-PEO block copolymer(F-127)on polyvinylidene fluoride(PVDF)was investigated in the process of adsorption of macromolecules.The influence of the concentration of the good solvent on the adsorption was investigated.The experiments showed that the more F-127 were adsorbed under swelling conditions and the adsorption capacity of polymers increased with an increase in the good solvent concentration.Macromolecules adsorbed under non-swelling conditions were easily desorbed,while macromolecules adsorbed under swelling conditions were relatively stable planted on the polymer surface.Hemocompatibility experiments showed that PVDF membrane had better anti-protein pollution and lower platelet and red blood cell adhesion rate after adsorption under swelling conditions,and the hemolysis rate was only 0.28%.