Sliding Friction of Zwitterionic Hydrogel and Its Electrostatic Origin
Sliding Friction of Zwitterionic Hydrogel and Its Electrostatic Origin
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DOI：
10.1021/ma500382y
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发表时间：
2014-05-13
期刊：
影响因子：
5.5
通讯作者：
Gong, Jian Ping
中科院分区：
文献类型：
--
作者：
Ahmed, Jamil;Guo, Honglei;Gong, Jian Ping
聚两性离子材料在聚合物的每个重复单元中同时具有阳离子和阴离子基团，表现出优异的抗生物污损性能。在这项研究中，羧基甜菜碱型两性离子水凝胶，聚（N-（羧甲基）-N，N-二甲基-2-（甲基丙烯酰氧基）-乙铵，内盐）（PCDME），对玻璃基板在水溶液中的表面摩擦进行了研究。使用具有平行板几何形状的流变仪进行摩擦测量，并且在测量期间监测滑动界面。在水中，玻璃表面的摩擦应力很高，只要两个滑动面完全接触，摩擦应力对压力的依赖性就很弱。在具有不同离子强度的溶液中进行的结果表明，玻璃基板上的高摩擦具有静电起源。静电电位测量表明，PCDME凝胶具有在pH 8.5的等电点。由于玻璃基板在纯水中带有负电荷，因此凝胶和玻璃在水中具有静电吸引力。对pH影响的研究表明，pH低于8.5时，带正电荷的凝胶和带负电荷的玻璃之间的吸引力产生高摩擦，而pH高于8.5时，两个带负电荷的表面之间的双电层排斥力产生低摩擦。从这些结果中，它的结论是，虽然PCDME凝胶的行为像中性凝胶的本体性质，其表面性质敏感地改变与介质的pH值和离子强度。
Polyzwitterionic materials, which have both cationic and anionic groups in each repeating unit of polymer, show excellent antibiofouling properties. In this study, the surface friction of carboxybetaine type zwitterionic hydrogels, poly(N-(carboxymethyl)-N,N-dimethy1-2-(methacryloyloxy)-ethanaminium, inner salt) (PCDME), against glass substrates were investigated in aqueous solutions. The friction measurement was performed using a rheometer with parallel plate geometry and the sliding interface was monitored during the measurement. The frictional stress on glass was high in water and it showed weak dependence on pressure as long as the two sliding surfaces were in complete contact. The results performed in solutions with varied ionic strength revealed that the high friction on glass substrates has an electrostatic origin. The electrostatic potential measurement revealed that the PCDME gels have an isoelectric point at pH 8.5. Since the glass substrates carrying negative charges in pure water, the gel and the glass have electrostatic attraction in water. Study on the effect of pH has shown that below pH 8.5, attraction between the positively charged gels and negatively charged glass gives high friction, while above pH 8.5, the electrical double layer repulsion between two negatively charged surfaces gives low friction. From these results, it is concluded that although the PCDME gels behave like neutral gels in the bulk properties, their surface properties sensitively change with pH and ionic strength of the medium.