Mangalara Jayachandra Hari, Simmons David S
Department of Polymer Engineering, The University of Akron, 250 South Forge Street, Akron, Ohio 44325-0301, United States.
ACS Macro Lett. 2015 Oct 20;4(10):1134-1138. doi: 10.1021/acsmacrolett.5b00635. Epub 2015 Sep 23.
Small-molecule diluents are important tools in the control of polymers' glass formation, transport, and mechanical properties. While recent work has indicated that these diluents can impose a more diverse range of effects than previously appreciated, use of these additives to rationally control polymer properties requires a predictive understanding of their effects. Here we employ molecular dynamics simulations to show that diluent-induced changes in a polymer's glass transition temperature can be predicted based on the diluent's Debye-Waller factor ⟨⟩, a measure of picosecond time scale rattle-space, via a functional form previously found to predict nanoconfinement-induced shifts in polymer . Moreover, we show that diluent-induced alterations in polymer segmental relaxation time are related to changes in modulus and ⟨⟩ via the Generalized Localization Model of relaxation. These results provide new design principles for the use of oligomeric diluents in achieving independent, targeted control of structural relaxation and glassy moduli.
小分子稀释剂是控制聚合物玻璃化形成、传输和机械性能的重要工具。虽然最近的研究表明，这些稀释剂所产生的影响范围比之前所认识到的更为多样，但要通过使用这些添加剂来合理控制聚合物性能，就需要对其效果有预测性的理解。在此，我们采用分子动力学模拟来表明，基于稀释剂的德拜-瓦勒因子⟨⟩（一种皮秒时间尺度下的晃动空间度量），可以通过先前发现的用于预测聚合物中纳米限域诱导位移的函数形式，预测稀释剂引起的聚合物玻璃化转变温度变化。此外，我们表明，稀释剂引起的聚合物链段弛豫时间变化，通过弛豫的广义局域化模型与模量变化和⟨⟩相关。这些结果为使用低聚稀释剂实现对结构弛豫和玻璃态模量的独立、靶向控制提供了新的设计原则。
