Densely packed polymer chains grafted to a substrate, especially polymer brushes, have been studied intensively. Of special interest are systems that react to changes in external conditions or”remember” previous conditions. With this focus, we explore the properties of PNiPAAm brushes and relate published work to own results. The co-nonsolvency effect leads to a collapse of a PNiPAAm brush for a certain mixing ratio of ethanol in water. This also influences the wetting behavior of PNiPAAm brushes. We show that through prewetting of a brush with different liquids (water and ethanol), the contact angle of subsequent water drops changes significantly. To explain this change, the swelling of the brush was investigated with spectroscopic ellipsometry and the orientation of the molecules at the surface with sum-frequency generation (SFG). Only little change in swelling was found. The SFG measurements reveal in the ethanol prewetted case a well ordered hydrophobic methyl layer at the interface, which is consistent with the contact angle measurement.

已经深入研究了接枝到基材上的密集聚合物链，尤其是聚合物刷。特别感兴趣的是对外部条件的变化做出反应或“记住”先前条件的系统。以此为重点，我们探索了 PNiPAAm 画笔的特性，并将已发表的工作与自己的结果联系起来。对于乙醇在水中的特定混合比例，共非溶解效应会导致 PNiPAAm 刷崩溃。这也会影响 PNiPAAm 刷子的润湿行为。我们表明，通过用不同的液体（水和乙醇）预润湿刷子，后续水滴的接触角会发生显着变化。为了解释这种变化，用光谱椭圆偏光法和和频生成 (SFG) 研究了刷子的膨胀和表面分子的取向。仅发现肿胀变化很小。SFG 测量显示，在乙醇预润湿的情况下，界面处有一个有序的疏水甲基层，这与接触角测量结果一致。