Interaction forces and molecular adhesion between pre-adsorbed poly(ethylene imine) layers
Interaction forces and molecular adhesion between pre-adsorbed poly(ethylene imine) layers
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DOI：
10.1016/j.jcis.2005.09.033
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发表时间：
2006-04-15
影响因子：
9.9
通讯作者：
Borkovec, M
中科院分区：
文献类型：
--
作者：
Pericet-Camara, R;Papastavrou, G;Borkovec, M
采用基于原子力显微镜（AFM）的胶体探针技术研究了不同分子量的支化聚乙烯亚胺（PEI）预吸附层之间的相互作用力。在接近过程中，由于扩散层的重叠，表面之间的长程力是排斥的，下降到几纳米的距离，从而观察到表面电荷的调节。所观察到的扩散层电位的离子强度依赖性可以用2.3 mC/m（2）的表面电荷来合理化。力保持排斥直到接触，这可能是由于PEI层之间的电空间相互作用。这些电空间力具有几纳米的范围，并且似乎与源自扩散层重叠的力叠加。在表面收缩期间，由于分子粘附事件（即，桥接粘附）。分子粘附事件的频率随着离子强度的增加而增加。PEI段的力响应由橡胶状延伸轮廓主导。对于低分子量PEI，在分离后立即在短距离处观察到强粘附力，而对于高分子量PEI，在较大距离处较弱的粘附力更常见。粘附功估计通过整合的回缩力的配置文件，并发现它与离子强度增加。(c)2005年爱思唯尔公司All rights reserved.
Interaction forces between pre-adsorbed layers of branched poly(ethylene imine) (PEI) of different molecular mass were studied with the colloidal probe technique, which is based on atomic force microscopy (AFM). During approach, the long-ranged forces between the surfaces are repulsive due to overlap of diffuse layers down to distances of a few nanometers, whereby regulation of the surface charge is observed. The ionic strength dependence of the observed diffuse layer potentials can be rationalized with a surface charge of 2.3 mC/m(2). The forces remain repulsive down to contact, likely due to electro-steric interactions between the PEI layers. These electro-steric forces have a range of a few nanometers and appear to be superposed to the force originating from the overlap of diffuse layers. During retraction of the surfaces, erratic attractive forces are observed due to molecular adhesion events (i.e., bridging adhesion). The frequency of the molecular adhesion events increases with increasing the ionic strength. The force response of the PEI segments is dominated by rubber-like extension profiles. Strong adhesion forces are observed for low molecular mass PEI at short distances directly after separation, while for high molecular mass weaker adhesion forces at larger distances are more common. The work of adhesion was estimated by integrating the retraction force profiles, and it was found to increase with the ionic strength. (c) 2005 Elsevier Inc. All rights reserved.