Schoustra Sybren K, Dijksman Joshua A, Zuilhof Han, Smulders Maarten M J
Laboratory of Organic Chemistry, Wageningen University Stippeneng 4 6708 WE Wageningen The Netherlands
Physical Chemistry and Soft Matter, Wageningen University Stippeneng 4 6708 WE Wageningen The Netherlands.
Chem Sci. 2020 Nov 3;12(1):293-302. doi: 10.1039/d0sc05458e.
In this work, we demonstrate that fine-grained, quantitative control over macroscopic dynamic material properties can be achieved using the Hammett equation in tuneable dynamic covalent polyimine materials. this established physical-organic principle, operating on the molecular level, one can fine-tune and control the dynamic material properties on the macroscopic level, by systematic variation of dynamic covalent bond dynamics through selection of the appropriate substituent of the aromatic imine building blocks. Five tuneable, crosslinked polyimine network materials, derived from dianiline monomers with varying Hammett parameter () were studied by rheology, revealing a distinct correlation between the value and a range of corresponding dynamic material properties. Firstly, the linear correlation of the kinetic activation energy ( ) for the imine exchange to the value, enabled us to tune the from 16 to 85 kJ mol. Furthermore, the creep behaviour (), glass transition ( ) and the topology freezing transition temperature ( ), all showed a strong, often linear, dependence on the value of the dianiline monomer. These combined results demonstrate for the first time how dynamic material properties can be directly tuned and designed in a quantitative - and therefore predictable - manner through correlations based on the Hammett equation. Moreover, the polyimine materials were found to be strong elastic rubbers (' > 1 MPa at room temperature) that were stable up to 300 °C, as confirmed by TGA. Lastly, the dynamic nature of the imine bond enabled not only recycling, but also intrinsic self-healing of the materials over multiple cycles without the need for solvent, catalysts or addition of external chemicals.
在这项工作中，我们证明了使用哈米特方程在可调动态共价聚亚胺材料中可以实现对宏观动态材料特性的细粒度定量控制。基于这一在分子水平上起作用的既定物理有机原理，通过选择芳族亚胺结构单元的合适取代基来系统改变动态共价键动力学，人们可以在宏观水平上微调并控制动态材料特性。通过流变学研究了五种由具有不同哈米特参数（）的二苯胺单体衍生的可调交联聚亚胺网络材料，揭示了值与一系列相应动态材料特性之间的明显相关性。首先，亚胺交换的动力学活化能（）与值的线性相关性使我们能够将从16 kJ mol调节到85 kJ mol。此外，蠕变行为（）、玻璃化转变（）和拓扑冻结转变温度（），都显示出对二苯胺单体的值有很强的、通常是线性的依赖性。这些综合结果首次证明了如何通过基于哈米特方程的相关性以定量且因此可预测的方式直接调整和设计动态材料特性。此外，如热重分析所证实的，发现聚亚胺材料是强弹性橡胶（室温下'> 1 MPa），在高达300°C时稳定。最后，亚胺键的动态性质不仅使材料能够循环利用，而且能够在多个循环中实现材料的固有自修复，而无需溶剂、催化剂或添加外部化学物质。
