Elter Maximilian, Brosz Matthias, Sucerquia Daniel, Kuzhelev Andrei, Kiesewetter Denis C, Kurth Markus, Dreuw Andreas, Prisner Thomas F, Freudenberg Jan, Bunz Uwe H F, Gräter Frauke
Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
Heidelberg Institute for Theoretical Studies, Schloß-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany.
J Am Chem Soc. 2024 Oct 9;146(40):27594-27599. doi: 10.1021/jacs.4c08765. Epub 2024 Sep 27.
Stronger chemical bonds withstand higher mechanical forces; thus, the rupture of single bonds is preferred over the rupture of double or triple bonds or aromatic rings. We investigated bond scission in poly(dialkyl--phenylene ethynylene)s (PPEs), a fully conjugated polymer. In a scale-bridging approach using electron-paramagnetic resonance spectroscopy and gel permeation chromatography of cryomilled samples, in combination with density functional theory calculations and coarse-grained simulations, we conclude that mechanical force cleaves the sp-sp bond of PPEs (bond dissociation energy as high as 600 kJ mol). Bond scission primarily occurs in shear bands with locally increased shear stresses. The scission occurs in the middle of the PPE chains. Breaking sp-sp bonds into free radicals thus is feasible but requires significant mechanical force and an efficient stress concentration.
更强的化学键能承受更高的机械力；因此，单键断裂比双键、三键或芳香环的断裂更易发生。我们研究了聚（二烷基 - 亚苯基乙炔）（PPEs）（一种完全共轭聚合物）中的键断裂情况。通过一种跨尺度方法，利用电子顺磁共振光谱和低温研磨样品的凝胶渗透色谱，结合密度泛函理论计算和粗粒度模拟，我们得出结论：机械力会切断PPEs的sp-sp键（键解离能高达600 kJ/mol）。键断裂主要发生在剪切应力局部增加的剪切带中。断裂发生在PPE链的中间。因此，将sp-sp键断裂成自由基是可行的，但需要巨大的机械力和有效的应力集中。
