Liquid Crystalline Vitrimers with Full or Partial Boronic‐Ester Bond Exchange,Advanced Functional Materials

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Liquid Crystalline Vitrimers with Full or Partial Boronic‐Ester Bond Exchange
Advanced Functional Materials ( IF 18.5 ) Pub Date : 2019-10-15 , DOI: 10.1002/adfm.201906458
Mohand O. Saed ₁ , Alexandra Gablier ₁ , Eugene M. Terentejv ₁

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In this manuscript, a new vitrimer chemistry strategy (boronic transesterification) is introduced into liquid crystal elastomers (LCEs) to allow catalyst‐free bond exchange to enable processing (director alignment, remolding, and welding) in the liquid crystalline (nematic) phase. Additionally, the concept of partial vitrimer network is explored, where a percolating fraction of the network remains permanently cross‐linked, hence preserving the integrity of the materials and preventing large creep. This combined strategy allows one to avoid the shortcomings of current methods of aligning LCE, especially in complex shapes. Thiol‐acrylate Michael addition reaction is used to produce uniform polymer networks with controllable thermomechanical response and local plasticity. Control of the plasticity is achieved by varying the fractions of permanent and exchangeable network, where a material “sweet spot” with an optimum elastic/plastic balance is identified. Such exchangeable LCE (xLCE) allows postpolymerization processing, while also minimizing unwanted creep during actuation. Moreover, conjoining multiple materials (isotropic and liquid‐crystalline) in a single covalently bonded composite structure results in a variety of smart morphing systems that adopt shapes with complex curvature. Remolding and welding xLCEs may enable the applications of these materials as mechanical actuators in reversibly folding origami, in vivo artificial muscles, and in soft robotics.

中文翻译：

具有全部或部分硼酸酯键交换的液晶晶振

在本手稿中，液晶弹性体（LCE）中引入了一种新的vitrimer化学策略（硼酸酯基转移反应），以允许无催化剂的键交换，从而能够在液晶（向列）相中进行处理（方向对准，重塑和焊接）。此外，还探索了部分微晶陶瓷网络的概念，其中网络的渗透部分保持永久交联，从而保留了材料的完整性并防止了大的蠕变。这种组合策略可以避免当前对齐LCE的方法的缺点，尤其是在复杂形状中。巯基丙烯酸酯迈克尔加成反应用于产生均匀的聚合物网络，该网络具有可控的热机械响应和局部可塑性。可塑性的控制是通过改变永久性和可交换网络的比例来实现的，其中可确定具有最佳弹性/塑性平衡的材料“最佳点”。这种可交换的LCE（xLCE）可以进行后聚合处理，同时还可以最大程度地减少驱动过程中不必要的蠕变。此外，在单个共价键合的复合结构中将多种材料（各向同性和液晶）结合在一起会导致形成各种智能变形系统，这些系统采用具有复杂曲率的形状。xLCE的重塑和焊接可以使这些材料作为机械致动器在可逆折纸，体内人造肌肉和软机器人中的应用。这种可交换的LCE（xLCE）可以进行后聚合处理，同时还可以最大程度地减少驱动过程中不必要的蠕变。此外，在单个共价键合的复合结构中将多种材料（各向同性和液晶）结合在一起会导致形成各种智能变形系统，这些系统采用具有复杂曲率的形状。xLCE的重塑和焊接可以使这些材料作为机械致动器在可逆折纸，体内人造肌肉和软机器人中的应用。这种可交换的LCE（xLCE）可以进行后聚合处理，同时还可以最大程度地减少驱动过程中不必要的蠕变。此外，在单个共价键合的复合结构中将多种材料（各向同性和液晶）结合在一起会导致形成各种智能变形系统，这些系统采用具有复杂曲率的形状。xLCE的重塑和焊接可以使这些材料作为机械致动器在可逆折纸，体内人造肌肉和软机器人中的应用。

更新日期：2020-01-17

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