Wang Yimin, Ma Ruibin, Li Haoxiang, Hu Shikai, Gao Yangyang, Liu Li, Zhao Xiuying, Zhang Liqun
State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, 100029 Beijing, P. R. China.
Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, 100029 Beijing, P. R. China.
Soft Matter. 2022 Jun 1;18(21):4090-4101. doi: 10.1039/d2sm00463a.
Due to the wide application, it is very crucial to understand the viscoelasticity of the polyurethane elastomer (PU, denoted by soft-hard block copolymer), which contains the soft segments (SS) and hard segments (HS). Thus, in this work, the effect of the content and strength of HS on the viscoelasticity of PU is explored in detail by adopting a coarse-grained model. First, the phase morphology of PU is characterized where both the single continuous phase and the bicontinuous phase are observed by varying the content of HS. Then, the viscoelasticity of PU is calculated by analyzing the storage modulus, the loss modulus, and the loss factor, which depends on the content and strength of HS. To further elucidate the mechanism for the storage modulus, the normalized interaction energy, the order parameter, and the formation probability of the HS or SS phase are characterized with the shear strain amplitude, which reflects the deformation of the phase structure. Then, the energy dissipation is quantified, which can rationalize the loss modulus well. A parameter is introduced, which considers the relative slippage and the content of HS or SS. It can explain the change in the loss factor with the content and strength of HS. In summary, this work can help to further understand how the content and strength of hard segments affect the viscoelasticity of the soft-hard block PU and structure evolution at the molecular level.
由于聚氨酯弹性体（PU，由软硬嵌段共聚物表示）的广泛应用，了解其粘弹性非常关键，该弹性体包含软段（SS）和硬段（HS）。因此，在本工作中，采用粗粒化模型详细探究了硬段的含量和强度对PU粘弹性的影响。首先，通过改变硬段含量来表征PU的相形态，观察到了单连续相和双连续相。然后，通过分析储能模量、损耗模量和损耗因子来计算PU的粘弹性，这些模量取决于硬段的含量和强度。为了进一步阐明储能模量的机制，用反映相结构变形的剪切应变幅值来表征归一化相互作用能、序参数以及硬段或软段相的形成概率。然后，对能量耗散进行量化，这可以很好地解释损耗模量。引入了一个参数，该参数考虑了相对滑移以及硬段或软段的含量。它可以解释损耗因子随硬段含量和强度的变化。总之，这项工作有助于进一步理解硬段的含量和强度如何在分子水平上影响软硬嵌段PU的粘弹性和结构演变。
