The Bimodal Energy Landscape When Polymers Adsorb
The Bimodal Energy Landscape When Polymers Adsorb
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聚合物吸附时的双峰能量景观
作者：
Hildegard M. Schneider;P. Frantz;S. Granick
我们描述了当柔性聚合物吸附比表面结构平衡更快时产生的链构象的直方图。通过红外分析模型系统（聚甲基丙烯酸甲酯主要通过氢键吸附在氧化硅上）的构象基态，测量了该直方图，发现它是双峰的。一大群链分散成扁平的构象。第二大链群在吸附时发现可用的自由表面较少，因此变得更加脆弱。吸附的历史依赖性可以理解为对具有柔性形状的物体的不可逆吸附。这种解释与使自由能最小化的传统考虑有决定性的不同。
We describe the histogram of chain conformations that results when flexible polymers adsorb more quickly than the surface structure equilibrates. By infrared analysis of conformational substates in a model system (poly(methyl methacrylate) adsorbed primarily by hydrogen bonding onto oxidized silicon), this histogram was measured and found to be bimodal. One large population of chains spread into flattened conformations. A second large population of chains, finding less free surface available at the time of adsorption, became attached more tenuously. The history dependence of adsorption could be understood as the irreversible adsorption of objects with flexible shape. This interpretation differs decisively from the traditional considerations of minimizing the free energy.