University of Bremen, Institute for Physical and Theoretical Chemistry, Leobener Straße NW2, D-28359, Bremen, Germany.
Current address: University of Bremen, UFT, Leobener Str. 6, D-28359, Bremen, Germany.
Chemphyschem. 2020 Nov 3;21(21):2402-2406. doi: 10.1002/cphc.202000739. Epub 2020 Oct 7.
Flex-activated mechanophores can be used for small-molecule release in polymers under tension by rupture of covalent bonds that are orthogonal to the polymer main chain. Using static and dynamic quantum chemical methods, we here juxtapose three different mechanical deformation modes in flex-activated mechanophores (end-to-end stretching, direct pulling of the scissile bonds, bond angle bendings) with the aim of proposing ways to optimize the efficiency of flex-activation in experiments. It is found that end-to-end stretching, which is a traditional approach to activate mechanophores in polymers, does not trigger flex-activation, whereas direct pulling of the scissile bonds or displacement of adjacent bond angles are efficient methods to achieve this goal. Based on the structural, energetic and electronic effects responsible for these observations, we propose ways of weakening the scissile bonds experimentally to increase the efficiency of flex-activation.
在张力下，通过切断与聚合物主链正交的共价键，可利用柔性机械增感剂将小分子从聚合物中释放出来。本研究采用静态和动态量子化学方法，将柔性机械增感剂中的三种不同机械变形模式（末端拉伸、末端单键直接拉伸、键角弯曲）并列在一起，旨在提出优化实验中柔性激活效率的方法。研究发现，传统的在聚合物中激活机械增感剂的末端拉伸方法不能触发柔性激活，而末端单键的直接拉伸或相邻键角的位移则是实现这一目标的有效方法。基于导致这些观察结果的结构、能量和电子效应，我们提出了在实验中削弱单键的方法，以提高柔性激活的效率。
