Factors controlling the growth of polyelectrolyte multilayers
Factors controlling the growth of polyelectrolyte multilayers
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DOI：
10.1021/ma981927a
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发表时间：
1999-11-30
期刊：
影响因子：
5.5
通讯作者：
Schlenoff, JB
中科院分区：
文献类型：
--
作者：
Dubas, ST;Schlenoff, JB
评价了聚电解质多层厚度与盐浓度、盐种类、溶剂质量、沉积时间和聚合物浓度的关系。聚合物沉积在旋转硅片上。对于所研究的强聚阳离子/聚阴离子对，膜厚度与层数和盐浓度近似成正比。整体分子吸附的不可逆性表现为溶液聚合物的表面（放射性标记）缺乏交换。聚合物吸附驱动力的疏水性通过选择盐反离子或溶剂来说明。在离子交换的框架内分析，离子对形成的净能量不高，最多只有几kT。盐与聚合物片段竞争表面，允许局部重排，在提出的机制中，多余的聚合物被容纳在几层中，而不是在一层环和尾部中。空间位阻与缓慢的构象变化是聚合物长期吸附的原因。考虑到其无序性和互渗性，多层沉积与固相或共沉淀的多电解质复合物有许多共同之处。使用含氟表面活性剂作为反离子可增强表面疏水性。
The dependence of polyelectrolyte multilayer thickness on salt concentration, salt type, solvent quality, deposition time, and polymer concentration is evaluated. Polymers are deposited on spinning silicon wafers. For the strong polycation/polyanion pair studied, film thickness is approximately proportional to the number of layers and the salt concentration. The irreversibility of overall molecule adsorption is indicated by the lack of exchange of surface (radiolabeled) for solution polymer. The hydrophobic nature of the driving force for polymer sorption is illustrated by the choice of salt counterion or solvent. Analyzed within the framework of ion exchange, the net energy of ion pair formation is not high, at most a few kT. Salt, competing with polymer segments for the surface, permits localized rearrangements, in the mechanism proposed, excess polymer is accommodated within several layers, rather than in one layer of loops and tails. Steric barriers coupled with slow conformational changes are responsible for long-term polymer adsorption. Considering the disorder and interpenetration, multilayer buildup has much in common with solution phase or coprecipitated polyelectrolyte complexes. Surface hydrophobicity can be enhanced using fluorinated surfactants as counterions.