PH-DEPENDENT INTERACTIONS BETWEEN ADSORBED CHITOSAN LAYERS
PH-DEPENDENT INTERACTIONS BETWEEN ADSORBED CHITOSAN LAYERS
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DOI：
10.1021/la00041a027
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发表时间：
1992-05-01
期刊：
影响因子：
3.9
通讯作者：
NINHAM, BW
中科院分区：
文献类型：
--
作者：
CLAESSON, PM;NINHAM, BW
壳聚糖是甲壳素经碱处理N-脱乙酰基后得到的阳离子交联剂。利用表面力技术研究了壳聚糖在水溶液中的吸附及壳聚糖层间的相互作用。将带负电荷的云母表面浸入含有0.01重量%壳聚糖的0.01重量%乙酸溶液中。壳聚糖的吸附导致平坦的吸附层和表面电荷的符号反转。对于随后的稀释，吸附基本上是不可逆的。稀释后，吸附壳聚糖层之间的作用力的pH依赖性进行了研究。壳聚糖-云母系统在pH 6.2左右不带电荷（壳聚糖的pK（a）约为6.5）。在此pH值下，壳聚糖涂覆的表面之间存在弱的吸引相互作用。力与距离曲线的最小值位于约20-25埃的间隔处。在较小的分离处观察到空间排斥。在较低和较高的pH值的长程相互作用是由一个排斥的双层力，分别来自壳聚糖和云母表面上的电荷占主导地位。从表面力测量获得的信息使我们能够建议在不同pH值的不可逆吸附层的结构。层结构的pH依赖性是合理的，在段-段和段-表面相互作用的变化。
Chitosan is a cationic polyelectrolyte obtained after N-deacetylation of chitin by alkaline treatment. The adsorption of chitosan and the interaction between chitosan layers have been investigated using a surface force technique. Negatively charged mica surfaces were immersed in a 0.01 wt % acetic acid solution containing 0.01 wt % chitosan. The adsorption of chitosan results in a flat adsorbed layer and a reversal of the sign of the surface charge. The adsorption is essentially irreversible with respect to subsequent dilution. After dilution, the pH dependence of the forces acting between the adsorbed chitosan layers was investigated. The chitosan-mica system is uncharged around pH 6.2 (the pK(a) of chitosan is around 6.5). At this pH there is a weak attractive interaction between the chitosan-coated surfaces. The minimum in the force vs distance curve is located at a separation of about 20-25 angstrom. A steric repulsion is observed at smaller separations. At lower and higher pH values the long-range interaction is dominated by a repulsive double-layer force originating from charges on chitosan and on the mica surface, respectively. The information obtained from surface force measurements allows us to suggest a structure of the irreversibly adsorbed layer at various pH values. The pH dependence of the layer structure is rationalized in terms of changes in segment-segment and segment-surface interactions.