School of Chemical Engineering, Pusan National University, Busan 46241, Republic of Korea.
Department of Chemical Engineering and Biotechnology, Tech University of Korea, Siheung-Si, Gyeonggi-Do 15073, Republic of Korea.
ACS Macro Lett. 2023 Jul 18;12(7):968-973. doi: 10.1021/acsmacrolett.3c00112. Epub 2023 Jun 30.
Linear and nonlinear viscoelastic properties of star polystyrene (PS) melts with unentangled arms were measured by using small-amplitude and medium-amplitude oscillatory shear (SAOS and MAOS) tests. For comparison purposes, such tests were also conducted on entangled linear and star PS melts. Interestingly, the linear viscoelastic properties of unentangled star PS were quantitatively described using the Lihktman-McLeish model for entangled linear chains, indicating that unentangled stars were indistinguishable from linear chains by using relaxation spectra. By contrast, the relative intrinsic nonlinearity (), one of the MAOS material functions, exhibited a difference between unentangled star and linear PS. When the maximum value () was plotted against the entanglement number of span molecules (), unentangled star PS exhibited larger values than linear PS, which was quantitatively predicted via the multimode K-BKZ model. Therefore, in the unentangled regime, star PS was concluded to be characterized by intrinsically higher relative nonlinearity than linear PS.
采用小振幅和中振幅振荡剪切（SAOS 和 MAOS）测试测量了无缠结臂星形聚苯乙烯（PS）熔体的线性和非线性黏弹性性质。为了比较目的，还对缠结线性和星形 PS 熔体进行了此类测试。有趣的是，使用用于缠结线性链的 Lihktman-McLeish 模型对无缠结星形 PS 的线性黏弹性性质进行了定量描述，表明通过松弛谱，无缠结的星形与线性链无法区分。相比之下，相对固有非线性度（），MAOS 材料函数之一，在无缠结星形和线性 PS 之间表现出差异。当最大值（）相对于跨度分子的缠结数（）绘制时，无缠结星形 PS 表现出比线性 PS 更大的值，这通过多模 K-BKZ 模型进行了定量预测。因此，在无缠结状态下，星形 PS 被认为具有比线性 PS 更高的固有相对非线性度。
