Department of Chemistry, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou 310018, China.
ACS Macro Lett. 2022 Aug 16;11(8):1041-1048. doi: 10.1021/acsmacrolett.2c00263. Epub 2022 Aug 3.
Dry polymer brushes have attracted great attention because of their potential utility in regulating interface properties. However, it is still unknown whether dry polymer brushes will exhibit degrafting behavior as a result of thermal annealing. Herein, a study of the conformational entropy effect on thermal degrafting of dry polystyrene (PS) brushes is presented. For PS brushes with an initial grafting density (σ) of 0.61 nm, degrafting behavior was observed at 393 K, and the equilibrium σ was approximately 0.14 nm at 413 K. However, for brushes with σ ≤ 0.14 nm, thermal degrafting was not observed even if the temperature was increased to 453 K. Furthermore, we found that the degrafting rate was faster for PS brushes with higher σ and higher molecular weights when σ > 0.14 nm. Our findings confirmed that degrafting is a mechanochemical activation process driven by tension imposed on bonds that anchor the chains to the surface, and the process is amplified by conformational entropy.
干燥聚合物刷因其在调节界面性质方面的潜在应用而受到极大关注。然而，干燥聚合物刷在热退火下是否会表现出解缠结行为仍不得而知。在此，研究了构象熵对干燥聚苯乙烯（PS）刷热解缠结的影响。对于初始接枝密度（σ）为 0.61nm 的 PS 刷，在 393K 下观察到解缠结行为，在 413K 下平衡 σ约为 0.14nm。然而，对于 σ≤0.14nm 的刷子，即使温度升高到 453K，也没有观察到热解缠结。此外，我们发现当 σ＞0.14nm 时，具有较高 σ 和较高分子量的 PS 刷的解缠结速率更快。我们的研究结果证实，解缠结是一种由链与表面锚定的键上的张力引起的机械化学活化过程，并且该过程通过构象熵放大。
