Millisecond photorefractivity with novel dicyanomethylenedihydrofuran-containing polymers
作者:Francisco Gallego-Gómez、Julio C. Álvarez-Santos、José L. Rodríguez-Redondo、Enrique Font-Sanchis、José M. Villalvilla、Ángela Sastre-Santos、María A. Díaz-García、Fernando Fernández-Lázaro
DOI:10.1039/c2jm31320k
日期:——
New multifunctional copolymers containing carbazole units and high loads of dicyanomethylenedihydrofuran (DCDHF) were synthesized and used to prepare blends for photorefractive (PR) purposes. The materials response, which is strongly dependent on the glass-transition temperature (Tg), was thoroughly analyzed by holography, conductivity and ellipsometry measurements in order to both determine the limiting factors and optimize the performance. Materials that have a Tg around room temperature show strongly hindered chromophore orientation, which is avoided by lowering the Tg down to 6 °C, without compromising the PR effect or the material stability. A further DCDHF-containing homopolymer without carbazole was synthesized and characterized, showing an inferior PR response, which is attributed to a beneficial role for charge generation and transport of the attached carbazole in the copolymers. The new blends strongly improve the structural properties of previous DCDHF-based materials, allowing application of fields well above 100 V μm−1 and preventing beam fanning. Outstanding PR performance was achieved, with fast buildup and erasure times of a few tens of milliseconds (even at low recording intensities), large refractive index modulation (over 10−2) and two-beam coupling gain (above 350 cm−1). Such performance is among the best reported for PR materials based on multifunctional and nonlinear polymers and comparable to standard PR composites.
我们合成了含有咔唑单元和高含量二氰基甲酰二氢呋喃(DCDHF)的新型多功能共聚物,并将其用于制备光折射(PR)用途的混合物。材料的响应与玻璃转化温度(Tg)密切相关,我们通过全息、电导和椭偏仪测量对材料的响应进行了深入分析,以确定限制因素并优化性能。Tg 约为室温的材料显示出强烈的发色团取向受阻现象,通过将 Tg 降低到 6 °C,可以避免这种现象,而不会影响 PR 效果或材料的稳定性。我们还合成了另一种不含咔唑的含 DCDHF 均聚物,并对其进行了表征,结果显示 PR 反应较差,这是因为共聚物中附着的咔唑有利于电荷的产生和传输。新的共混物极大地改善了以前基于 DCDHF 的材料的结构特性,使电场的应用远高于 100 V μm-1,并防止了光束扇形。这种材料具有出色的 PR 性能,即使在记录强度较低的情况下,也能实现几十毫秒的快速建立和擦除时间、较大的折射率调制(超过 10-2)和双光束耦合增益(超过 350 cm-1)。据报道,这种性能是基于多功能和非线性聚合物的 PR 材料中最好的,可与标准 PR 复合材料相媲美。