Reorganization of an Amphiphilic Glassy Polymer Surface in Contact with Water Probed by Contact Angle and Sum Frequency Generation Spectroscopy

We address the question of how a surface of a glassy polymer reorganizes after coming in contact with water. Because contact angle hysteresis measurements are also affected by surface roughness and chemical heterogeneity, we have used surface-sensitive sum frequency generation spectroscopy (SFG) in conjunction with water contact angles to answer this question. To increase the magnitude of the surface reorganization, we have designed an amphiphilic polymer, poly(α-hydroxymethyl-n-butyl acrylate) (PHNB), to study the changes in the structure of polar hydroxy groups and nonpolar (methyl and methylene) groups at the interface. The SFG and the water contact angles show that reorganization does occur for PHNB below Tg. However, complete reorganization requires heating the sample above the bulk Tg. These heating experiments were conducted by first heating the sample in the presence of water and then followed by cooling the sample to room temperature in the presence of water to lock the changes in the surface str...

我们探讨玻璃态聚合物表面与水接触后如何重组的问题。由于接触角滞后测量也受表面粗糙度和化学不均匀性的影响，我们结合水接触角使用了表面敏感的和频产生光谱（SFG）来回答这个问题。为了增加表面重组的程度，我们设计了一种两亲性聚合物，聚（α - 羟甲基 - 正丁基丙烯酸酯）（PHNB），以研究界面处极性羟基以及非极性（甲基和亚甲基）基团结构的变化。SFG和水接触角表明，在低于玻璃化转变温度（Tg）时，PHNB确实会发生重组。然而，完全重组需要将样品加热到本体Tg以上。这些加热实验是先在有水的情况下加热样品，然后在有水的情况下将样品冷却到室温，以锁定表面结构的变化……