Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.
Institute for Soldier Nanotechnologies , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.
J Am Chem Soc. 2018 May 23;140(20):6501-6508. doi: 10.1021/jacs.8b03777. Epub 2018 May 15.
Materials with magneto-optic (MO) properties have enabled critical fiber-optic applications and highly sensitive magnetic field sensors. While traditional MO materials are inorganic in nature, new generations of MO materials based on organic semiconducting polymers could allow increased versatility for device architectures, manufacturing options, and flexible mechanics. However, the origin of MO activity in semiconducting polymers is far from understood. In this paper, we report high MO activity observed in a chiral helical poly-3-(alkylsulfone)thiophene (P3AST), which confirms a new design for the creation of a giant Faraday effect with Verdet constants up to (7.63 ± 0.78) × 10 deg T m at 532 nm. We have determined that the sign of the Verdet constant and its magnitude are related to the helicity of the polymer at the measured wavelength. The Faraday rotation and the helical conformation of P3AST are modulated by thermal annealing, which is further supported by DFT calculations and MD simulations. Our results demonstrate that helical polymers exhibit enhanced Verdet constants and expand the previous design space for polythiophene MO materials that was thought to be limited to highly regular lamellar structures. The structure-property studies herein provide insights for the design of next-generation MO materials based upon semiconducting organic polymers.
具有磁光（MO）性质的材料已经实现了关键的光纤应用和高灵敏度磁场传感器。虽然传统的 MO 材料是无机的，但基于有机半导体聚合物的新一代 MO 材料可以为器件结构、制造选项和灵活的机械结构提供更高的多功能性。然而，半导体聚合物中 MO 活性的起源远未得到理解。在本文中，我们报告了在手性螺旋聚 3-(烷基亚砜)噻吩（P3AST）中观察到的高 MO 活性，这证实了通过Verdet 常数高达（7.63±0.78）×10 deg T m 在 532nm 处创建巨大 Faraday 效应的新设计。我们已经确定Verdet 常数的符号和大小与在测量波长下聚合物的螺旋性有关。P3AST 的 Faraday 旋转和螺旋构象通过热退火进行调制，这进一步得到了 DFT 计算和 MD 模拟的支持。我们的结果表明，螺旋聚合物表现出增强的Verdet 常数，并扩展了先前被认为仅限于高度规则层状结构的聚噻吩 MO 材料的设计空间。本文的结构-性能研究为基于有机半导体聚合物的下一代 MO 材料的设计提供了见解。
