Micromechanical Characterization of Zwitterionic Polymer Brushes Based on the Atomic Force Microscopy

Clinical applications of interventional catheters suffer from poor lubricity and nonspecific protein adhesion, which can cause severe damage to soft tissues and even life-threatening injuries. With the proposed strategy in the grafting of sulfobetaine methacrylate (SBMA) zwitterionic polymer brushes using dopamine (DA) and sodium alginate (SA) as an intermediate layer, the pDASA-SBMA brush coatings with a controlled increase in density and thickness were prepared by tuning the grafting time. Based on the atomic force microscopy (AFM) technique, we systematically investigate the effect of variations in structural parameters on the swelling and nanomechanical properties of brushes. In particular, the dependence of the lateral deformability of brush chains on structural parameters and the viscoelastic relaxation behavior of the brush chains to recover their equilibrium conformation after deformation are elucidated, both of which have an impact on friction measurements. The experimental results show that the coating adhesion and friction coefficient in pure water decrease with the increase in grafting time, which is caused by the increase in hydration lubrication capacity of dense and thick brushes, as well as the weakening of lateral deformability. With the grafting of 24 h, the adhesion and friction coefficient of the coating can be reduced by 80 % and 91 %, respectively, compared to the unmodified surfaces. With the significant friction reduction and anti-adhesion effects, the proposed surface coating technique can find versatile applications in high-performance interventional catheters.