Demonstrating the Interfacial Polymer Thermal Transition from Coil-to-Globule to Coil-to-Stretch under Shear Flow Using SFG and MD Simulation
writer：Yongsheng Luo, Ai-Ping Pang, Peizhi Zhu, Dayang Wang, Xiaolin Lu*
keywords：Polymer Brushes,Coil-to-globule, Coil-to-stretch, SFG, Microfuidics, MD simulation,
source：期刊
specific source：J. Phys. Chem. Lett. 2022, 13, 1617–1627.
Issue time：2022年
Revealing interfacial shear-induced structural responsiveness has long been an important topic in that most fluids in nature and human life are in motion and cause interesting boundary phenomena. An amazing one is how the polymer chain conformation or local structural feature at a boundary changes under the effective shear condition. In this study, microfluidic-assisted sum frequency generation (SFG) vibrational spectroscopy and all-atom molecular dynamics (MD) simulation are combined to reveal that the shear flow can effectively block the so-called thermal coil-to-globule transition of the poly(N-isopropylacrylamide) (PNIPAM) brushes on the solid substrate; while the normal coil-to-globule transition transfers to a coil-to-stretch one under the shear flow with increasing the ambient temperature. Such findings are attributed to the balance between the shear flow and the molecular interaction with respect to the polymer chains and adjacent water molecules, thus demonstrating the significant effect of the shear flow on the structural and dynamic behaviors of the polymer chains at the boundaries from the molecular level.
https://pubs.acs.org/doi/10.1021/acs.jpclett.1c03866