Tian Houkuan, Luo Jintian, Tang Qiyun, Zha Hao, Priestley Rodney D, Hu Wenbing, Zuo Biao
School of Chemistry and Chemical Engineering, Key Laboratory of Surface & Interface Science of Polymer Materials of Zhejiang Province, Zhejiang Sci-Tech University, Hangzhou, 310018, China.
Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University, Nanjing, 211189, China.
Nat Commun. 2024 Jul 19;15(1):6082. doi: 10.1038/s41467-024-50398-7.
Over the past three decades, studies have indicated a mobile surface layer with steep gradients on glass surfaces. Among various glasses, polymers are unique because intramolecular interactions - combined with chain connectivity - can alter surface dynamics, but their fundamental role has remained elusive. By devising polymer surfaces occupied by chain loops of various penetration depths, combined with surface dissipation experiments and Monte Carlo simulations, we demonstrate that the intramolecular dynamic coupling along surface chains causes the sluggish bulk polymers to suppress the fast surface dynamics. Such effect leads to that accelerated segmental relaxation on polymer glass surfaces markedly slows when the surface polymers extend chain loops deeper into the film interior. The surface mobility suppression due to the intramolecular coupling reduces the magnitude of the reduction in glass transition temperature commonly observed in thin films, enabling new opportunities for tailoring polymer properties at interfaces and under confinement and producing glasses with enhanced thermal stability.
在过去三十年中，研究表明玻璃表面存在具有陡峭梯度的移动表面层。在各种玻璃中，聚合物是独特的，因为分子内相互作用与链连接性相结合可以改变表面动力学，但其基本作用仍然难以捉摸。通过设计由不同穿透深度的链环占据的聚合物表面，结合表面耗散实验和蒙特卡罗模拟，我们证明沿表面链的分子内动态耦合导致迟缓的本体聚合物抑制快速的表面动力学。这种效应导致当表面聚合物将链环更深地延伸到薄膜内部时，聚合物玻璃表面上加速的链段弛豫明显减慢。由于分子内耦合导致的表面迁移率抑制降低了薄膜中通常观察到的玻璃化转变温度降低的幅度，为在界面处和受限条件下定制聚合物性能以及生产具有增强热稳定性的玻璃提供了新的机会。
