Title: Red-light-Controllable Liquid-Crystal Soft Actuators via Low-power Excited Upconversion Based on Triplet-Triplet Annihilation

Author: Zhen Jiang , Ming Xu , Fuyou Li*, Yanlei Yu*

Journal: J. Am. Chem. Soc., 2013, 135(44), 16446-16453

Abstract:

A red-light-controllable soft actuator has been achieved, driven by low-power excited triplet-triplet annihilation-based upconversion luminescence (TTA-UCL). First, a red-to-blue TTA-based upconversion system with a high absolute quantum yield of 9.3 ± 0.5% was prepared by utilizing platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP) as the sensitizer and 9,10-bis(diphenylphosphoryl)anthracene (BDPPA) as the annihilator. In order to be employed as a highly effective phototrigger of photodeformable cross-linked liquid-crystal polymers (CLCPs), the PtTPBP&BDPPA system was incorporated into a rubbery polyurethane film and then assembled with an azotolane-containing CLCP film. The generating assembly film bent toward the light source when irradiated with a 635 nm laser at low power density of 200 mW cm–2 because the TTA-UCL was effectively utilized by the azotolane moieties in the CLCP film, inducing their trans–cis photoisomerization and an alignment change of the mesogens via an emission–reabsorption process. It is the first example of a soft actuator in which the TTA-UCL is trapped and utilized to create photomechanical effect. Such advantages of using this novel red-light-controllable soft actuator in potential biological applications have also been demonstrated as negligible thermal effect and its excellent penetration ability into tissues. This work not only provides a novel photomanipulated soft actuation material system based on the TTA-UCL technology but also introduces a new technological application of the TTA-based upconversion system in photonic devices.

论文链接：https://pubs.acs.org/doi/abs/10.1021/ja406020r

PDF下载：Red-light-Controllable Liquid Crystal Soft Actuators via Low-power Excited Upconversion Based on Triplet-Triplet Annihilation.pdf

本研究中，我们证明了可以利用三线态-三线态湮灭上转换发光(TTA-UCL)系统作为低功率激发的长波长光触发器，进而制备光敏交联液晶聚合物(CLCP)。首先，我们实现了一种高效的红-蓝型TTA上转换系统，该系统具有低能量激发光源和9.3 ± 0.5%的高绝对量子产率。为了将其作为偶氮苯CLCP的光触发器，TTA-UCL系统被加入到橡胶聚氨酯薄膜中，然后与含偶氮苯的CLCP薄膜组装在一起。由于TTA-UCL被CLCP膜中的偶氮苯有效利用，其发散-再吸收过程会诱导顺反光致异构化并导致液晶基元的排列改变。因此制备的复合膜在低功率635 nm红光的照射下，会朝着光源方向发生弯曲变形。这种新型的红光可控软执行器于潜在生物应用中的优势还体现在其微不足道的热效应和对组织的优异渗透能力。