Surface self-assembled zwitterionization of poly(vinylidene fluoride) microfiltration membranes via hydrophobic-driven coating for improved blood compatibility

A facile surface self-assembled zwitterionization process is presented, aiming at improving the blood compatibility of poly(vinylidene fluoride) (PVDF) membranes. Zwitterionic diblock copolymers containing hydrophobic propylene oxide and hydrophilic sulfobetaine methacrylate blocks were prepared with well controlled molecular weights via atom-transfer radical polymerization (ATRP). Poly(propylene oxide)-block-poly(sulfobetaine methacrylate) (PPO-b-PSBMA) copolymers with varying zwitterionic PSBMA lengths were coated by self-assembling process onto the surface of PVDF microfiltration membranes in order to enhance their surface hydrophilicity and protein resistance. A systematic study regarding the effect of block lengths of PPO-b-PSBMA copolymers on the hemocompatibility of zwitterionic PVDF membranes in human blood solution was then performed. Protein adsorption from single-protein solutions and 100% blood plasma solutions was measured on the PVDF surfaces covered with PPO-b-PSBMA brushes. If the increase in PPO content in copolymer increased the efficiency of coating on the membrane, resistance to human fibrinogen adsorption was enhanced when increasing the PSBMA content. The control of the anchoring structures of zwitterionic copolymer layers highly regulates the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. PVDF membranes coated with PPO-b-PSBMA containing a high amount of zwitterionic SBMA units presented a high hydration capability, believed to allow improving significantly the hemocompatible character of PVDF membranes. This work suggests that the hemocompatible nature of self-assembled zwitterionic brushes gives them a great potential in the molecular design of antithrombogenic membranes for use in human blood applications.