Auxetic materials have negative Poisson’s ratios and so expand rather than contract in one or several direction(s) perpendicular to applied extensions. The auxetics community has long sought synthetic molecular auxetics – non-porous, inherently auxetic materials which are simple to fabricate and avoid porosity-related weakening. Here, we report, synthetic molecular auxeticity for a non-porous liquid crystal elastomer. For strains above ~0.8 applied perpendicular to the liquid crystal director, the liquid crystal elastomer becomes auxetic with the maximum negative Poisson’s ratio measured to date being -0.74 ± 0.03 – larger than most values seen in naturally occurring molecular auxetics. The emergence of auxeticity coincides with the liquid crystal elastomer backbone adopting a negative order parameter, QB = -0.41 ± 0.01 – further implying negative liquid crystal ordering. The reported behaviours consistently agree with theoretical predictions from Warner and Terentjev liquid crystal elastomer theory. Our results open the door for the design of synthetic molecular auxetics.
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机译：辅助材料的泊松比为负，因此在垂直于所应用延伸的一个或多个方向上扩展而不是收缩。修长学界一直在寻求合成分子修长学–无孔，固有的修身材料，这些材料易于制造并且避免了与孔隙率相关的削弱。在这里，我们报告了无孔液晶弹性体的合成分子膨胀性。对于垂直于液晶指向矢施加的高于0.8的应变，液晶弹性体会发生膨胀，迄今为止测得的最大负泊松比为-0.74±±0.03 –大于自然发生的分子膨胀中的大多数值。膨胀性的出现与采用负阶参数QB order = -0.41±0.01的液晶弹性体骨架相吻合-进一步暗示了液晶的负序。报告的行为与Warner和Terentjev液晶弹性体理论的理论预测一致。我们的结果为合成分子动力学设计打开了大门。
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