Effect of substituting non-polar chains with polar chains on the structural dynamics of small organic molecule and polymer semiconductors.
Effect of substituting non-polar chains with polar chains on the structural dynamics of small organic molecule and polymer semiconductors.
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DOI：
10.1039/d1cp00670c
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发表时间：
2021-03
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影响因子：
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通讯作者：
Anne A. Y. Guilbert;Zachary S. Parr;T. Kreouzis;Duncan J. Woods;Reiner Sebastian Sprick;I. Abrahams;C. Nielsen;M. Zbiri
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文献类型：
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作者：
Anne A. Y. Guilbert;Zachary S. Parr;T. Kreouzis;Duncan J. Woods;Reiner Sebastian Sprick;I. Abrahams;C. Nielsen;M. Zbiri
有机半导体的可加工性和光电性能可以通过化学设计来调节和操纵。用低聚醚取代常用的烷基侧链最近已成功地用于生物电子传感器和光催化析氢等应用。除了极性的差异之外，低聚醚中的碳-氧键可能使系统更柔软，更容易发生动力学紊乱，这可能对例如电荷传输有害。在这种情况下，我们使用中子光谱作为探测的主要方法，除了表征技术，如X射线衍射，差示扫描量热法和偏光显微镜，以研究三甘醇（TEG）链取代正己基（Hex）链对两种有机半导体材料的结构动力学的影响：亚苯基-联噻吩-亚苯基（PTTP）小分子和芴-co-二苯并噻吩（FS）聚合物。与直觉相反，非弹性中子散射（INS）揭示了PTTP和FS材料与六角链的模式的一般软化，指向一个增加的动力学无序的六角为基础的系统。然而，温度依赖性的X射线和中子衍射以及INS和差示扫描量热法的证据与TEG链的PTTP接近室温的额外的可逆转变。观察到的额外的结构转变，这是不伴随着双折射的变化，也可以观察到准弹性中子散射（QENS）。在PTTP而不是FS的情况下观察到TEG链动力学的紧固。因此，我们分配这个过渡到熔化的TEG链。总的来说，TEG链在室温下促进动力学有序，但如果结晶，可能会在室温以上引入额外的可逆结构转变，导致热不稳定性。最终，对链极性和结构动力学的更深入理解可以帮助指导新材料设计，并在电子电荷传输和水溶胀之间实现复杂的平衡，这是许多新兴的有机电子和生物电子应用所寻求的。
The processability and optoelectronic properties of organic semiconductors can be tuned and manipulated via chemical design. The substitution of the popular alkyl side chains by oligoethers has recently been successful for applications such as bioelectronic sensors and photocatalytic hydrogen evolution. Beyond the differences in polarity, the carbon-oxygen bond in oligoethers is likely to render the system softer and more prone to dynamical disorder that can be detrimental to charge transport for example. In this context, we use neutron spectroscopy as a master method of probe, in addition to characterisation techniques such as X-ray diffraction, differential scanning calorimetry and polarized optical microscopy to study the effect of the substitution of n-hexyl (Hex) chains by triethylene glycol (TEG) chains on the structural dynamics of two organic semiconducting materials: a phenylene-bithiophene-phenylene (PTTP) small molecule and a fluorene-co-dibenzothiophene (FS) polymer. Counterintuitively, inelastic neutron scattering (INS) reveals a general softening of the modes of PTTP and FS materials with Hex chains, pointing towards an increased dynamical disorder in the Hex-based systems. However, temperature-dependent X-ray and neutron diffraction as well as INS and differential scanning calorimetry evidence an extra reversible transition close to room temperature for PTTP with TEG chains. The observed extra structural transition, which is not accompanied by a change in birefringence, can also be observed by quasi-elastic neutron scattering (QENS). A fastening of the TEG chains dynamics is observed in the case of PTTP and not FS. We therefore assign this transition to the melt of the TEG chains. Overall the TEG chains are promoting dynamical order at room temperature, but if crystallising, may introduce an extra reversible structural transition above room temperature leading to thermal instabilities. Ultimately, a deeper understanding of chain polarity and structural dynamics can help guide new materials design and navigate the intricate balance between electronic charge transport and aqueous swelling that is being sought for a number of emerging organic electronic and bioelectronic applications.