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Force-Induced Transition of π–π Stacking in a Single Polystyrene Chain

2019; American Chemical Society; Volume: 141; Issue: 24 Linguagem: Inglês

10.1021/jacs.9b03490

1943-2984

Wanhao Cai, Duo Xu, Lu Qian, Junhao Wei, Chen Xiao, Linmao Qian, Zhong‐Yuan Lu, Shuxun Cui,

Carbon Nanotubes in Composites

Although π–π interactions have been studied for several decades, the quantification of the strength of π–π interactions in a macromolecule remains a big challenge. Herein, we utilize single-molecule atomic force microscopy and steered molecular dynamics simulations to study the π–π interactions in polystyrene (PS). It is found that in high vacuum, the single-chain mechanics of PS differs largely from that of polyethylene (PE). Accordingly, the strength of intrachain π–π interactions in PS is estimated to be 0.7 kcal/(mol stack), which is much lower than that in a small-molecule system (benzene dimer, 2–3 kcal/(mol stack)). Further study shows that in high vacuum, there are two types of π–π stacking in the single PS chain, i.e., the every-other-moiety (E) type and the adjacent-moiety (A) type. Upon force stretching, a transition from E-type to A-type π–π stacking can be observed.