Implications for Auxetic Response in Liquid Crystalline Polymers: X‐Ray Scattering and Space‐Filling Molecular Modeling,Physica Status Solidi (B) - Basic Solid State Physics

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Implications for Auxetic Response in Liquid Crystalline Polymers: X‐Ray Scattering and Space‐Filling Molecular Modeling
Physica Status Solidi (B) - Basic Solid State Physics ( IF 1.5 ) Pub Date : 2020-08-23 , DOI: 10.1002/pssb.202000261
Prateek Verma ₁ , Chaobin He ₂ , Anselm C. Griffin ₁

Affiliation

Five transverse rod (TR)‐containing main‐chain liquid crystalline polymers (LCPs) are examined in both the powder and fiber forms by wide angle X‐ray diffraction. Data from the diffraction experiments are consistent with the site‐connectivity‐driven TR‐reorientation mechanism for intrinsic auxetic character in these macromolecules. Shifts in peak maxima, intensity distributions in the interchain interaction region, and calculated volume increase accompanying fiber formation are all in line with expectations from considerations of this mechanism. The narrow window for experimental conditions necessary for fiber preparation and subsequent X‐ray observation of this phenomenon is detailed. A close examination of space‐filling Corey–Pauling–Koltun (CPK) molecular models reveals the details of local packing of rods and connected polymer chains in the quiescent nematic polymer melt prior to fiber drawing. It is found that two rod‐reorientation possibilities exist each of which leads to increased interchain separation as required for auxetic response. Suggestions for future experiments and materials design for new LCPs are described.

中文翻译：

液晶聚合物中助燃响应的含义：X射线散射和空间填充分子模型

通过广角X射线衍射检查了五种含横向棒（TR）的粉末状和纤维状主链液晶聚合物（LCP）。衍射实验的数据与这些大分子的固有膨胀特性的位点连接性驱动的TR重取向机制一致。峰最大值的变化，链间相互作用区域的强度分布以及伴随纤维形成的计算出的体积增加都符合从该机理考虑的预期。详细介绍了准备纤维和随后对该现象进行X射线观察所需的实验条件的狭窄窗口。对充满空间的Corey-Pauling-Koltun（CPK）分子模型的仔细检查揭示了在拉丝之前静态向列型聚合物熔体中棒和连接的聚合物链的局部堆积的细节。发现存在两种杆重新定向的可能性，每种可能性都会导致拉长响应所需的链间分离增加。描述了有关未来LCP的实验和材料设计的建议。

更新日期：2020-10-11

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