Guo Hongye, Saed Mohand O, Terentjev Eugene M
Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, UK.
Soft Matter. 2022 Jun 29;18(25):4803-4809. doi: 10.1039/d2sm00547f.
The Michael addition 'click' chemistry was used to graft acrylate-terminated mesogenic groups onto the polysiloxane backbone polymer chain with thiol functional groups, with a constant 15% fraction of diacrylate reacting monomers as crosslinkers. Three different types of mesogens were used, and also their 50 : 50 mixtures, and in all cases we have obtained the smectic-A phase of the resulting liquid crystalline elastomer. Using X-ray diffraction, calorimetry and dynamic mechanical analysis, we investigated the relationship between the molecular structure of mesogenic side groups and the structure and properties of the elastomers. The shape-memory of smectic elastomers was verified. The unusual features were the semi-crystalline nature of elastomers with non-polar mesogens and the clear role of side-by-side rod dimerization of polar mesogens leading to a higher smectic layer spacing. We investigated the evolution of the smectic alignment on uniaxial stretching along the layer normal and identified two distinct ways in which the elastomer responds: the coarsened Helfrich-Hurault zig-zag layer texture and the large-scale stripe domains of uniform layer rotation in the systems with lower order parameter and the associated layer constraints.
采用迈克尔加成“点击”化学方法，将丙烯酸酯封端的介晶基团接枝到具有硫醇官能团的聚硅氧烷主链聚合物链上，其中二丙烯酸酯反应单体作为交联剂的比例恒定为15%。使用了三种不同类型的介晶基团，以及它们的50:50混合物，在所有情况下，我们都得到了所得液晶弹性体的近晶-A相。通过X射线衍射、量热法和动态力学分析，我们研究了介晶侧基的分子结构与弹性体结构和性能之间的关系。验证了近晶弹性体的形状记忆性能。不寻常的特征是具有非极性介晶基团的弹性体的半结晶性质，以及极性介晶基团的并排棒状二聚化导致更高近晶层间距的明显作用。我们研究了沿层法线单轴拉伸时近晶排列的演变，并确定了弹性体响应的两种不同方式：在具有较低序参数和相关层约束的系统中，粗化的赫夫里希-于拉尔特之字形层纹理和均匀层旋转的大规模条纹域。
