Surface dilatational elasticity of poly(oxy ethylene)-based Surfactants by oscillation and relaxation measurements of sessile bubbles
Surface dilatational elasticity of poly(oxy ethylene)-based Surfactants by oscillation and relaxation measurements of sessile bubbles
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DOI：
10.1021/la7024582
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发表时间：
2008-01-01
期刊：
影响因子：
3.9
通讯作者：
Hansen, Finn Knut
中科院分区：
文献类型：
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作者：
Hansen, Finn Knut
用轴对称气泡形状法测量了表面的粘弹性和粘性。两种不同的技术，使用正弦振荡和步骤松弛已被使用，并通过体/表面扩散交换模型的结果进行处理。三种不同的非离子表面活性剂的基础上聚（氧乙烯）作为亲水基团已被使用：一个简单的表面活性剂，Brij 35，和两个嵌段共聚物，普朗尼克F68和P9400。阶跃松弛法和振荡法给出的极限面解析弹性基本相同，但阶跃松弛法是一种更依赖于模型的方法。在体/表面扩散模型正确的情况下，这两种方法给出相同的结果，但在其他情况下，阶跃松弛给出极限弹性E-0和典型松弛频率ω（0）的平均值。极限弹性高达约。已发现这些物质的浓度为25 mN m（-1）。表面/体扩散模型很好地描述了两种相对亲水的物质Brij 35和F68，特别是在低浓度下，但对于更疏水的P9400则不那么好。作为表面活性聚合物的表面压力的函数的表面构象弹性由于表面构象变化而经历至少一个最大值。
Surface dilatational elasticities and viscosities have been measured by means of the axisymmetric bubble shape method. Two different techniques using sinusoidal oscillations and step relaxations have been used, and the results are treated by means of the bulk/surface diffusional exchange model. Three different nonionic surfactants based on poly(oxy ethylene) as the hydrophilic group have been used: one simple surfactant, Brij 35, and two block copolymers, Pluronic F68 and P9400. Step relaxation and oscillation give mostly the same limiting surface dilatational elasticities, but step relaxation is a more model-dependent method. In the cases where the bulk/surface diffusion model is correct, the two methods give the same results, but otherwise step relaxation gives average values of the limiting elasticity E-0 and the typical relaxation frequency omega(0). Limiting elasticities up to ca. 25 mN m(-1) have been found for these substances. The surface/bulk diffusion model describes quite well the two relatively hydrophilic substances Brij 35 and F68, especially at low concentrations, but less so for the more hydrophobic P9400. The surface dilatational elasticity as a function of the surface pressure of the surface-active polymers goes, through at least one maximum as a result of surface conformational changes.