Wang Jing, Somasundaran P
NSF Industry/University Cooperative Research Center for Advanced Studies in Novel Surfactants, Columbia University, New York, NY 10027, USA.
J Colloid Interface Sci. 2005 Nov 1;291(1):75-83. doi: 10.1016/j.jcis.2005.04.095.
Carboxymethyl cellulose (CMC) is a polysaccharide which is widely used in many industrial sectors including food, textiles, paper, adhesives, paints, pharmaceutics, cosmetics and mineral processing. It is a natural organic polymer that is non-toxic and biodegradable. These properties make it ideal for industrial applications. However, a general lack of understanding of the interaction mechanism between the polysaccharides and solid surfaces has hindered the application of this polymer. In this work, adsorption of CMC at the solid-liquid interface is investigated using adsorption and electrophoretic mobility measurements, FTIR, fluorescence spectroscopy, AFM and molecular modeling. CMC adsorption on talc was found to be affected significantly by changes in solution conditions such as pH and ionic strength, which indicates the important role of electrostatic force in adsorption. The pH effect on adsorption was further proven by AFM imaging. Electrokinetic studies showed that the adsorption of CMC on talc changed its isoelectric point. Further, molecular modeling suggests a helical structure of CMC in solution while it is found to adsorb flat on the solid surface to allow its OH groups to be in contact with the surface. Fluorescence spectroscopy studies conducted to investigate the role of hydrophobic bonding using pyrene probe showed no evidence of the formation of hydrophobic domains at talc-aqueous interface. Urea, a hydrogen bond breaker, markedly reduced the adsorption of CMC on talc, supports hydrogen bonding as an important factor. In FTIR study, the changes to the infrared bands, associated with the CO stretch coupled to the CC stretch and OH deformation, were significant and this further supports the strong hydrogen bonding of CMC to the solid surface. In addition, Langmuir modeling of the adsorption isotherm suggests hydrogen bonding to be a dominant force for polysaccharide adsorption since the adsorption free energy of this polymer was close to that for hydrogen bond formation. All of the above results suggest that the main driving forces for CMC adsorption on talc are a combination of electrostatic interaction and hydrogen bonding rather than hydrophobic force.
羧甲基纤维素（CMC）是一种多糖，广泛应用于许多工业领域，包括食品、纺织、造纸、胶粘剂、涂料、制药、化妆品和矿物加工等。它是一种天然有机聚合物，无毒且可生物降解。这些特性使其成为工业应用的理想选择。然而，人们对多糖与固体表面之间相互作用机制的普遍缺乏了解，阻碍了这种聚合物的应用。在这项工作中，通过吸附和电泳迁移率测量、傅里叶变换红外光谱（FTIR）、荧光光谱、原子力显微镜（AFM）和分子模拟等方法，研究了CMC在固液界面的吸附情况。发现CMC在滑石粉上的吸附受溶液条件（如pH值和离子强度）变化的显著影响，这表明静电力在吸附过程中起着重要作用。AFM成像进一步证明了pH值对吸附的影响。电动研究表明，CMC在滑石粉上的吸附改变了其等电点。此外，分子模拟表明，CMC在溶液中呈螺旋结构，而在固体表面呈扁平吸附，使其羟基能够与表面接触。使用芘探针进行的荧光光谱研究，旨在探究疏水键的作用，结果表明在滑石粉 - 水界面没有形成疏水区域的证据。尿素作为一种氢键破坏剂，显著降低了CMC在滑石粉上的吸附，这支持了氢键是一个重要因素的观点。在FTIR研究中，与CO伸缩振动与CC伸缩振动以及OH变形相关的红外波段变化显著，这进一步支持了CMC与固体表面之间存在强氢键作用。此外，吸附等温线的朗缪尔模型表明，氢键是多糖吸附的主导力，因为该聚合物的吸附自由能接近氢键形成的自由能。上述所有结果表明，CMC在滑石粉上吸附的主要驱动力是静电相互作用和氢键的结合，而不是疏水作用力。
