Thermal Stability of π-Conjugated n-Ethylene-Glycol-Terminated Quaterthiophene Oligomers: A Computational and Experimental Study,ACS Macro Letters

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Thermal Stability of π-Conjugated n-Ethylene-Glycol-Terminated Quaterthiophene Oligomers: A Computational and Experimental Study
ACS Macro Letters ( IF 5.1 ) Pub Date : 2020-02-11 , DOI: 10.1021/acsmacrolett.9b00935
Mayank Misra , Ziwei Liu , Ban Xuan Dong ₁ , Shrayesh N Patel ₁ , Paul F Nealey ₁ , Christopher K Ober , Fernando A Escobedo

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This work represents a joint computational and experimental study on a series of n-ethylene glycol (PEOn)-terminated quaterthiophene (4T) oligomers for 1 < n < 10 to elucidate their self-assembly behavior into a smectic-like lamellar phase. This study builds on an earlier study for n = 4 that showed that our model predictions were consistent with experimental data on the melting behavior and structure of the lamellar phase, with the latter consisting of crystal-like 4T domains and liquid-like PEO4 domains. The present study aims to understand how the length of the terminal PEOn chains modulates the disordering temperature of the lamellar phase and hence the relative stability of the ordered structure. A simplified bilayer model, where the 4T domains are not explicitly described, is put forward to efficiently estimate the disordering effect of the PEO domains with increasing n; this method is first validated by correctly predicting that layers of alkyl (PE)-capped 4T oligomers (for 1 < n < 10) stay ordered at room temperature. Both 4T-domain implicit and explicit model simulations reveal that the order–disorder temperature decreases with the length of the PEO capping chains, as the associated increase in conformational entropy drives a tendency toward disorder that overtakes the cohesive energy, keeping the ordered packing of the 4T domains.

中文翻译：

π-共轭正乙二醇封端四噻吩低聚物的热稳定性：计算和实验研究

这项工作代表了对 1 < n < 10的一系列n-乙二醇 (PEO n ) 封端的四噻吩 (4T) 低聚物的联合计算和实验研究，以阐明它们的自组装行为成为近晶状层状相。这项研究建立在较早的n = 4 研究的基础上，该研究表明我们的模型预测与层状相熔化行为和结构的实验数据一致，后者由晶体状 4T 域和液体状 PEO4 域组成。本研究旨在了解终端 PEO n的长度如何链调节层状相的无序温度，从而调节有序结构的相对稳定性。提出了一种简化的双层模型，其中没有明确描述 4T 域，以有效估计 PEO 域随n增加的无序效应；该方法首先通过正确预测烷基 (PE) 封端的 4T 低聚物层（对于 1 < n < 10）在室温下保持有序来进行验证。4T 域隐式和显式模型模拟都表明，有序无序温度随着 PEO 封端链的长度而降低，因为相关的构象熵增加驱动了无序的趋势，超过了内聚能，保持了有序堆积4T 域。

更新日期：2020-02-11

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