Vyas Mukesh Kumar, Nandan Bhanu, Schneider Konrad, Stamm Manfred
Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, Dresden, Germany.
J Colloid Interface Sci. 2008 Dec 1;328(1):58-66. doi: 10.1016/j.jcis.2008.09.009. Epub 2008 Oct 1.
Wear studies were performed on polystyrene (PS)-poly(acrylic acid) (PAA) mixed polymer brushes and corresponding monobrushes in a dried state. The aim was to study the wear mechanism in polymer brush surfaces as well as to investigate the effect of switching of PS + PAA binary brush surfaces (on treatment with the selective solvents for the PS and PAA) on the wear process. Wear experiments were carried out using atomic force microscopy (AFM) under a controlled environment. The wear experiments were performed as a function of scan number using a sharp silicon nitride tip to induce the wear on the sample surfaces. The wear mechanism on different brush surfaces was influenced by molecular entanglement as well as adhesion and friction on the sample surface. The wear process on the PS monobrush surface treated with toluene took place via formation of the ripples. On the other hand, a typical wear mode observed on the PAA monobrushes was removal of the polymeric material from the surface. For the mixed brush surface treated with toluene (selective solvent for PS) where PS chains dominated the top of the sample surface, the typical wear mode observed was ripple formation similar to that observed for the PS monobrushes. However, when a mixed brush was treated with ethanol and pH 10 water so that PAA chains dominated the top layer, wear occurred via removal of material. The amount of wear on the surfaces increased with the number of scans. Furthermore, the load and scan velocity dependence of the wear process was also investigated. Wear on polymer brush surfaces increased on increasing the load and/or decreasing the scan speed. The present study shows that wear can be controlled/tuned using mixed responsive brushes.
在干燥状态下对聚苯乙烯（PS）-聚丙烯酸（PAA）混合聚合物刷及相应的单聚合物刷进行了磨损研究。目的是研究聚合物刷表面的磨损机制，以及研究PS + PAA二元刷表面切换（用PS和PAA的选择性溶剂处理）对磨损过程的影响。磨损实验在可控环境下使用原子力显微镜（AFM）进行。磨损实验是使用尖锐的氮化硅尖端在样品表面引发磨损，作为扫描次数的函数进行的。不同刷表面的磨损机制受分子缠结以及样品表面的粘附和摩擦影响。用甲苯处理的PS单聚合物刷表面的磨损过程是通过形成波纹发生的。另一方面，在PAA单聚合物刷上观察到的典型磨损模式是聚合物材料从表面去除。对于用甲苯（PS的选择性溶剂）处理的混合刷表面，其中PS链在样品表面顶部占主导，观察到的典型磨损模式是类似于PS单聚合物刷的波纹形成。然而，当混合刷用乙醇和pH 10的水处理，使PAA链在顶层占主导时，磨损通过材料去除发生。表面的磨损量随扫描次数增加。此外，还研究了磨损过程对负载和扫描速度的依赖性。聚合物刷表面的磨损随负载增加和/或扫描速度降低而增加。本研究表明，可以使用混合响应刷来控制/调节磨损。
