Shear forces between tethered polymer chains as a function of compression, sliding velocity, and solvent quality
Shear forces between tethered polymer chains as a function of compression, sliding velocity, and solvent quality
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DOI：
10.1021/ma011207v
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发表时间：
2003-01-28
期刊：
影响因子：
5.5
通讯作者：
Tirrell, M
中科院分区：
文献类型：
--
作者：
Schorr, PA;Kwan, TCB;Tirrell, M
用表面力仪(SFA)测量了在良好和接近Theta的溶剂中，端系在相对表面上的聚苯乙烯链间的剪切力。当剪切速度变化时，聚合物/溶剂复合体系以类牛顿方式响应，剪切力随剪切速度线性增加。在这种类牛顿体系中，末端系留体系的有效粘度比等分子量自由链的半稀溶液的粘度大一个数量级。在较大的剪切速度或较高的压缩程度下，布朗动力学模拟表明，界面宽度将变薄，导致剪切力随滑动速度的次线性增加。实验的局限性阻碍了用布朗动力学方法模拟的较高剪切速度的探索，但增加的限制最终导致了次线性行为，与模拟预测一致。
The shear forces between polystyrene chains end-tethered to opposing surfaces have been measured with the surface forces apparatus (SFA) in both good and near-Theta solvents. When the shearing velocity was varied, the complex polymer/solvent system responded in a Newtonian-like fashion with the shear force increasing linearly with the shear velocity. The effective viscosity of the end-tethered systems in this Newtonian-like regime was found to be an order of magnitude greater than the viscosity of semidilute solutions of equivalent molecular weight free chains. At larger shear velocities or higher extents of compression, Brownian dynamics simulations suggest the interfacial width will thin, leading to a sublinear increase in the shear force with sliding velocity. Experimental limitations prevented exploration of the higher shear velocities simulated with the Brownian dynamics approach, but increasing confinement eventually did lead to sublinear behavior, in agreement with the simulation prediction.