接枝-游离态两性离子聚合物刷的制备及润滑特性研究

人工关节中常用高交联聚乙烯(HXLPE)髋臼杯和陶瓷关节头组成摩擦副. 为改善表面间润滑性能，采用紫外光诱导接枝法在HXLPE表面制备接枝态聚(2-甲基丙烯酰氧乙基磷酰胆碱)两性离子聚合物刷(PMPC)，PMPC溶液作为润滑剂，使摩擦界面存在游离态PMPC，研究接枝-游离态PMPC协同作用对摩擦副润滑特性的影响. 进一步为了模拟人体组织液中金属离子的影响，研究了Na+、Ca2+和Al3+对人工关节摩擦副表面间PMPC润滑特性的影响规律. 结果表明：在3 N载荷下，人工关节摩擦副表面间仅用接枝态PMPC进行润滑时，摩擦系数为0.158，且波动频繁，当接枝-游离态PMPC协同作用于摩擦副表面时，摩擦系数降低为0.072，且在120 min试验时长内保持稳定. 在载荷为2 N时，接枝-游离态PMPC协同作用时的摩擦系数为0.046，当润滑剂中添加低价金属离子Na+与Ca2+时，摩擦系数略微增加，而添加高价金属离子Al3+时，致PMPC各分子间吸引力增大而破坏其原有水合层均匀性，使得摩擦系数增至0.118，为无金属离子干扰接枝-游离态PMPC协同作用时的2.5倍.

Friction pairs composed of highly cross-linked polyethylene (HXLPE) acetabular cups and ceramic femoral heads are commonly used in artificial joints. To improve the lubrication performance between surfaces, ultraviolet light-induced grafting was used to prepare zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) polymer brushes (PMPC) in grafted state on the surface of HXLPE. Using PMPC solution as the lubricant allowed free PMPC to exist at the friction interface, and the effect of the synergistic action of grafted and free PMPC on the lubrication characteristics of the friction pair was investigated. To further simulate the effect of metal ions in human body fluid, the influence rules of Na+, Ca2+ and Al3+ on the PMPC-mediated lubrication characteristics between the surfaces of artificial joint friction pairs were studied. The results showed that under a load of 3 N, the friction coefficient was 0.158 with frequent fluctuations when only grafted PMPC was used for lubrication between the surfaces of the artificial joint friction pair. When the synergistic action of grafted and free PMPC was applied to the friction pair surfaces, the friction coefficient decreased to 0.072 and remained stable throughout the 120-minute test duration. Under a load of 2 N, the friction coefficient was 0.046 under the synergistic action of grafted and free PMPC. When low-valent metal ions Na+ and Ca2+ were added to the lubricant, the friction coefficient increased slightly. When high-valent metal ion Al3+ was added, the intermolecular attraction of PMPC increased, destroying the uniformity of its original hydration layer, leading to an increase in the friction coefficient to 0.118, which was 2.5 times that of the synergistic action of grafted and free PMPC without metal ion interference.