Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
Department of Integrated Science and Technology, Faculty of Science and Technology, Oita University, 700 Dannoharu, Oita 870-1192, Japan.
Langmuir. 2020 Jun 16;36(23):6494-6501. doi: 10.1021/acs.langmuir.0c00854. Epub 2020 May 18.
A highly effective aqueous lubrication strategy employing electrostatic assembly of a negatively charged ultrahigh molecular weight natural polysaccharide named "sacran" and a positively charged poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMTAC) brush was investigated. The PMTAC brush was compressed through the adsorption of sacran to produce the layered structure of a PMTAC brush/sacran hybrid bottom layer and a poorly hydrated sacran top layer. The dynamic friction coefficients of the PMTAC brush were drastically reduced in salt-free sacran aqueous solutions, and the lubrication mode transition from the brush-lubrication regime to hydrodynamic lubrication was promoted. The electrostatic assembly was inhibited by the addition of NaCl into the lubricant solutions, leading to the loss of the lubrication effect. The hydrodynamic lubrication would be encouraged by the local viscosity enhancement at the friction boundary due to the poorly hydrated and highly viscous PMTAC brush/sacran hybrid film produced by the spontaneous electrostatic assembly.
采用静电组装带负电荷的超高相对分子质量天然多糖“壳聚糖”和带正电荷的聚[2-(甲基丙烯酰氧)乙基三甲基氯化铵]（PMTAC）刷的高效水润滑策略进行了研究。PMTAC 刷通过吸附壳聚糖被压缩，从而产生 PMTAC 刷/壳聚糖混合底层的层状结构和水合不良的壳聚糖顶层。在无盐壳聚糖水溶液中，PMTAC 刷的动摩擦系数急剧降低，润滑模式从刷润滑状态向流体动力润滑转变得到促进。向润滑剂溶液中添加 NaCl 会抑制静电组装，从而导致润滑效果丧失。由于自发静电组装产生的水合不良和高粘度的 PMTAC 刷/壳聚糖混合膜，在摩擦边界处局部粘度增加，会鼓励流体动力润滑。
