利用中子散射监测光照对共轭高分子凝胶结构的影响
Summary
本文提出了一种由光电共轭聚合物聚 (3-吩-25-酚) (P3HT) 组成的凝胶的分析方法, 利用小超小型角中子散射在光照的存在和缺乏的情况下进行。
Abstract
我们演示了一个协议, 以有效地监测高浓度的共轭聚合物溶液在存在和没有白光照射的凝胶过程。通过建立一个受控的温度斜坡, 这些材料的凝胶可以精确地监测, 因为它们进行这种结构演变, 有效地反映了在有机电子设备制造。利用小角中子散射 (san) 和超小型角中子散射 (USANS) 以及适当的拟合协议, 我们对整个过程中选择结构参数的演化进行了量化。透彻的分析表明, 在整个凝胶过程中持续的光暴露会显著改变最终形成的凝胶的结构。具体来说, 聚 (3-吩-25-酚) (P3HT) 纳米级集料的聚合过程受到光照的影响, 最终导致共轭高分子微结构的生长迟缓和形成小规模的宏观聚集群。
Introduction
共轭聚合物承诺功能材料, 可用于广泛的设备, 如有机发光二极管, 有机半导体, 化学传感器, 有机光伏。1,2,3,4,5,6在这些设备中, 性能的一个重要方面是在活动层中的固态共轭聚合物的有序和包装。7,8,9,10,11,12,13,14这种形态主要是由溶液中的聚合物链的构象以及随着这些溶液被浇铸到基材和溶剂被去除而演化的结构所预先确定的。通过研究在一个合适的溶剂中的模型光电聚合物的典型溶胶-凝胶过渡的结构, 这些系统可以有效地建模, 并对材料沉积过程中发生的自组装进行定量的一瞥。可以获得。15,16,17,18,19,20
具体来说, 我们研究的共轭聚合物基准 P3HT 在溶剂氘邻二氯苯 (管理局), 一个高分子溶剂系统, 已广泛使用, 因为它适合各种有机电子器件制造技术.23,24,25在给定的溶剂环境中, P3HT 链开始聚集在适当的环境刺激上, 如温度降低或溶剂质量损失。这一装配过程的确切机制正在调查中, 其中一个主要的建议路径被认为是一个渐进的过程, 其中单个 P3HT 分子π堆叠形成层状纳米聚集体称为 nanofibrils, 然后他们自己凝聚形成更大的微米级宏观集料。24了解这些通路, 形成的结构是正确预测和影响最佳器件活性层形态形成的关键。
针对这一最终目标, 更精确地指导这些主动层结构的形成, 有需要开发额外的实验和工业方法, 无损改变共轭聚合物形态原位。一个相对较新的方法中心围绕使用光曝光作为一种廉价的手段来改变聚合物链的形态, 同时计算和实验结果都指向它的可行性。25,26,27我们的实验室最近的工作表明, 在稀释溶液中存在着对光诱导的共轭聚合物-溶剂相互作用的改变, 从而导致聚合物链尺寸在光照时发生显著变化。30,31在这里, 我们提出了一个协议来继续这项工作, 通过有效地监测暴露一个更集中的共轭聚合物溶液的影响, 直接光整个凝胶过程, 是由恒温控制的指示温度斜坡我们使用中子散射, 因为它允许对聚合物-溶剂溶胶-凝胶系统的结构参数进行稳健的分析, 从埃到微米, 这种能力不可能通过其他更常见的流变或光谱学工具方法.16,17,30,31因此, 通过比较正确分析的小和超小型角中子数据, 将在光照下形成的凝胶组装成完全黑暗中收集的相同数据, 由光照驱动引起的结构差异可以全面确定和量化效果。
Protocol
Representative Results
Discussion
首先, 将 san 数据看作是温度的函数, 在椭圆柱模型的比例因子的增加表明, nanofibril 相中的 P3HT 量有明显的增加, 这与凝胶过程的进展 isconsistent.同时, 自由链 Rg的减少与 Porod 指数的增加相匹配, 表明随着温度的降低, 热力学条件的恶化导致了 P3HT 链中仍然存在的链坍塌解决.这些结果, 结合 USANS 数据显示 macroaggregate Rg在温度下降时的显著增加, 表明散射实验有效地捕获和分析了结构自…
Disclosures
The authors have nothing to disclose.
Acknowledgements
作者衷心感谢国家科学基金会 (DMR-1409034) 对该项目的支持。我们还感谢美国商务部国家标准和技术研究所的支持, 提供了这项工作所用的 USANS 设施, 其中部分由国家科学基金会根据协议予以支持。笑DMR-0944772这项研究的 san 实验是在 ORNL 的高通量同位素反应器中完成的, 该反应堆是由美国能源部的科学用户设施分部、能源科学办公室主办的。
Materials
| M(106) poly(3-hexylthiophene-2,5-diyl) (P3HT) | Ossila | 104934-50-1 | Conjugated polymer |
| deuterated 1,2 ortho-dichlorobenzene (ODCB) | Sigma Aldrich | AC321260050 | solvent |
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