Sundaram Vivek, Lyulin Alexey V, Baumeier Björn
Department of Mathematics and Computer Science, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
J Phys Chem B. 2020 Dec 3;124(48):11030-11039. doi: 10.1021/acs.jpcb.0c06787. Epub 2020 Nov 19.
We develop an all-atom force field for a series of diketopyrrolopyrrole polymers with two aromatic pyridine substituents and a variable number of π-conjugated thiophene units in the backbone (DPP2PyT), used as donor materials in organic photovoltaic devices. Available intrafragment parameterizations of the individual fragment building blocks are combined with interfragment bonded and nonbonded parameters explicitly derived from density functional theory calculations. To validate the force field, we perform classical molecular dynamics simulations of single polymer chains with = 1, 2, 3 in good and bad solvents and of melts. We observe the expected dependence of the chain conformation on the solvent quality, with the chain collapsing in water, and swelling in chloroform. The glass-transition temperature for the polymer melts is found to be in the range of 340-370 K. Analysis of the mobility of the conjugated segments in the polymer backbone reveals two relaxation processes: a fast one with a characteristic time at room temperature on the order of 10 ps associated with nearly harmonic vibrations and a slow one on the order of 100 ns associated with temperature-activated cis-trans transitions.
我们为一系列具有两个芳香吡啶取代基且主链中噻吩π共轭单元数量可变的二酮吡咯并吡咯聚合物（DPP2PyT）开发了一种全原子力场，该聚合物用作有机光伏器件中的供体材料。将各个片段构建块的可用片段内参数化与明确从密度泛函理论计算得出的片段间键合和非键合参数相结合。为了验证该力场，我们对在良溶剂和不良溶剂中以及熔体中具有(n = 1)、(2)、(3)的单聚合物链进行了经典分子动力学模拟。我们观察到链构象对溶剂质量的预期依赖性，链在水中收缩，在氯仿中膨胀。发现聚合物熔体的玻璃化转变温度在(340 - 370)K范围内。对聚合物主链中共轭链段迁移率的分析揭示了两个弛豫过程：一个快速过程，其在室温下的特征时间约为(10)皮秒，与近乎简谐振动相关；另一个缓慢过程，约为(100)纳秒，与温度激活的顺反转变相关。
