Fengyuan Zhang, Junliang Zhang*, Kuan Zhang, Xiao Zhong, Mukun He, Hua Qiu and Junwei Gu*. Highly Thermally Conductive Liquid Crystalline Epoxy Resin Vitrimers with Reconfigurable, Shape-Memory, Photo-Thermal, and Closed-Loop Recycling Performance. Advanced Science, 2024, 10.1002/advs.202410362. 2023IF=14.3.
https://onlinelibrary.wiley.com/doi/10.1002/advs.202410362
Abstract
The low thermal conductivity, poor toughness, and non-reprocessability of thermosetting epoxy resins severely restrict their applications and sustainable development in flexible electronics. Herein, liquid crystalline epoxy (LCE) and dynamic ester and disulfide bonds are introduced into the cured network of bisphenol A epoxy resin (E-51) to construct highly thermally conductive flexible liquid crystalline epoxy resin (LCER) vitrimers. LCER vitrimers demonstrate adjustable mechanical properties by varying the ratio of LCE to E-51, allowing it to transition from soft to strong. Typically, a 75 mol% LCE to 25 mol% E-51 ratio results in an in-plane thermal conductivity (λ) of 1.27 W m-1K-1, over double that of pure E-51 vitrimer (0.61 W m-1K-1). The tensile strength and toughness increase 2.88 folds to 14.1 MPa and 2.45 folds to 20.1 MJ m-3, respectively. Besides, liquid crystalline phase transition and dynamic covalent bonds enable triple shape memory and three-dimensional shape reconstruction. After four reprocessing cycles, λ and tensile strength remain at 94% and 72%, respectively. Integrating carbon nanotubes (CNTs) imparts photo-thermal effect and enables “on” and “off” switch under near-infrared (NIR) light to LCER vitrimer. Furthermore, the CNTs/LCER vitrimer displays light-induced actuation, self-repairing, and self-welding besides the closed-loop recycling and rapid degradation performance.
传统热固性环氧树脂的低本征导热性能、低韧性、不可再加工和回收性严重限制了其在柔性电子领域的应用和可持续发展。本研究将液晶环氧（LCE）与动态共价键（酯键和二硫键）引入到通用双酚A型环氧树脂（E-51）固化网络中，制备了具有可再加工和回收性的柔性高本征导热液晶环氧（LCER）类玻璃高分子。通过调节LCE与E-51的比例，LCER类玻璃高分子表现出可调控的机械性能，能够从软弹性体过渡到强韧体。当LCE与E-51的比例为75 mol%：25 mol%时，LCER兼具出色的导热性能和机械性能，其面内导热系数为1.27 W m-1 K-1，超过E-51（0.61 W m-1K-1）的两倍；拉伸强度和韧性分别提高到14.1 MPa和20.1 MJ m-3，是E-51的2.88和2.45倍。同时，液晶独特的相变性和动态共价键的可交换性赋予LCER三重形状记忆、3D永久形状重构等功能，经过四次重塑的导热系数和拉伸强度可分别保持在原始性能的94%和72%。此外， LCER中0.5 wt%碳纳米管（CNTs）的加入，使其具有稳定的光热转换性能，并能在808 nm的近红外光下实现可控“开”和“关”切换。同时，CNTs/LCER 类玻璃高分子在近红外光下能够实现精准光致驱动、形状记忆、局部自修复和自焊接，并可以实现闭环回收和快速降解。
论文亮点
1. 将LCE与动态共价键（酯键和二硫键）引入到通用双酚A型环氧树脂（E-51）固化网络中，制备了具有可再加工和回收性的柔性本征高导热液晶环氧树脂（LCER）类玻璃高分子。
2.当LCE与E-51的摩尔比为3：1时，LCER的面内导热系数为1.27 W m-1K-1，超过E-51（0.61 W m-1K-1）的两倍；拉伸强度和韧性分别提高到14.1 MPa和20.1 MJ m-3，是E-51的2.88和2.45倍。
3. 含0.5 wt% CNTs的LCER具有优异的光热转换功能，且能在808 nm 的近红外光源下实现可控“开”和“关”切换、精准光致驱动、形状记忆、局部自修复和自焊接，并能实现闭环回收和快速降解。
第一作者：张峰源
邮件地址：zfy0019@mail.nwpu.edu.cn
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