Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, People's Republic of China.
Department of Polymer Science and Engineering, Jiaxing University, Jiaxing 314001, P. R. China.
Soft Matter. 2018 Mar 28;14(12):2379-2390. doi: 10.1039/c7sm02282d. Epub 2018 Mar 5.
Designing a multiple-network structure at the molecular level to tailor the mechanical properties of polymeric materials is of great scientific and technological importance. Through the coarse-grained molecular dynamics simulation, we successfully construct an interpenetrating polymer network (IPN) composed of a flexible polymer network and a stiff polymer network. First, we find that there is an optimal chain stiffness for a single network (SN) to achieve the best stress-strain behavior. Then we turn to study the mechanical behaviors of IPNs. The result shows that the stress-strain behaviors of the IPNs appreciably exceed the sum of that of the corresponding single flexible and stiff network, which highlights the advantage of the IPN structure. By systematically varying the stiffness of the stiff polymer network of the IPNs, optimal stiffness also exists to achieve the best performance. We attribute this to a much larger contribution of the non-bonded interaction energy. Last, the effect of the component concentration ratio is probed. With the increase of the concentration of the flexible network, the stress-strain behavior of the IPNs is gradually enhanced, while an optimized concentration (around 60% molar ration) of the stiff network occurs, which could result from the dominant role of the enthalpy rather than the entropy. In general, our work is expected to provide some guidelines to better tailor the mechanical properties of the IPNs made of a flexible network and a stiff network, by manipulating the stiffness of the stiff polymer network and the component concentration ratio.
在分子水平上设计多网络结构以调整聚合物材料的机械性能具有重要的科学和技术意义。通过粗粒化分子动力学模拟，我们成功构建了由柔性聚合物网络和刚性聚合物网络组成的互穿聚合物网络（IPN）。首先，我们发现对于单个网络（SN），存在一个最佳的链刚性，以实现最佳的应力-应变行为。然后，我们转向研究 IPN 的力学行为。结果表明，IPN 的应力-应变行为明显超过相应的单个柔性和刚性网络的总和，这突出了 IPN 结构的优势。通过系统地改变 IPN 中刚性聚合物网络的刚性，也存在最佳的刚性以实现最佳性能。我们将其归因于非键相互作用能的更大贡献。最后，研究了组分浓度比的影响。随着柔性网络浓度的增加，IPN 的应力-应变行为逐渐增强，而刚性网络的优化浓度（约 60%摩尔比）出现，这可能是由于焓而不是熵起主导作用。总的来说，我们的工作有望通过操纵刚性聚合物网络的刚性和组分浓度比，为更好地调整由柔性网络和刚性网络组成的 IPN 的机械性能提供一些指导。
