Bull David S, Nelson Nathaniel, Konetski Danielle, Bowman Christopher N, Schwartz Daniel K, Goodwin Andrew P
Department of Chemical and Biological Engineering , University of Colorado , Boulder , Colorado 80309 , United States.
J Phys Chem Lett. 2018 Aug 2;9(15):4239-4244. doi: 10.1021/acs.jpclett.8b01723. Epub 2018 Jul 16.
Whereas nanobubble stability on solid surfaces is thought to be based on local surface structure, in this work, we show that nanobubble stability on polymer brushes does not appear to require contact-line pinning. Glass surfaces were functionalized with copolymer brushes containing mixtures of hydrophobic and hydrophilic segments, exhibiting water contact angles ranging from 10 to 75°. On unmodified glass, dissolution and redeposition of nanobubbles resulted in reformation in mostly the same locations, consistent with the contact line pinning hypothesis. However, on polymer brushes, the nucleation sites were random, and nanobubbles formed in new locations upon redeposition. Moreover, the presence of stable nanobubbles was correlated with global surface wettability, as opposed to local structure, when the surface exceeded a critical water contact angle of 50 or 60° for polymers containing carboxyl or sulfobetaine groups, respectively, as hydrophilic side chains. The critical contact angles were insensitive to the identity of the hydrophobic segments.
虽然人们认为纳米气泡在固体表面的稳定性基于局部表面结构，但在这项工作中，我们表明纳米气泡在聚合物刷上的稳定性似乎并不需要接触线钉扎。用含有疏水和亲水链段混合物的共聚物刷对玻璃表面进行功能化处理，其水接触角范围为10°至75°。在未改性的玻璃上，纳米气泡的溶解和再沉积导致其大多在相同位置重新形成，这与接触线钉扎假说一致。然而，在聚合物刷上，成核位点是随机的，纳米气泡在再沉积时会在新的位置形成。此外，当表面分别超过含有羧基或磺基甜菜碱基团作为亲水侧链的聚合物的临界水接触角50°或60°时，稳定纳米气泡的存在与整体表面润湿性相关，而不是与局部结构相关。临界接触角对疏水链段的种类不敏感。
