A recyclable polyurethane with characteristic thermal stiffening behavior via B-N coordination with reversible B-O bonds  

基于B–N配位作用与可逆B–O键协同构筑具有独特热增强行为的可回收聚氨酯

作　　者：Hui Xiong Linjun Zhang Qi Wu Jinrong Wu 熊慧;张林军;兀琪;吴锦荣(College of Polymer Science and Engineering,State Key Laboratory of Polymer Materials Engineering,Sichuan University,Chengdu 610065,China;Key Laboratory of Composite Materials on Electrical Insulation,National Energy Administration,Jiangsu Shemar Electric Co.,Ltd.,Nantong 226017,China)

机构地区：[1]College of Polymer Science and Engineering,State Key Laboratory of Polymer Materials Engineering,Sichuan University,Chengdu 610065,China [2]Key Laboratory of Composite Materials on Electrical Insulation,National Energy Administration,Jiangsu Shemar Electric Co.,Ltd.,Nantong 226017,China

出　　处：《Science China Materials》2024年第10期3339-3346,共8页中国科学（材料科学）（英文版）

基　　金：supported by the National Natural Science Foundation of China(52203064 and 52373061);the China Postdoctoral Science Foundation(2023M732415);the Fundamental Research Funds for the Central Universities(2022SCU12011);the State Key Laboratory of Polymer Materials Engineering,Sichuan University。

摘　　要：Thermal softening is an inevitable process in the physical network.Polyurethane(PU),a typical commercial material,is constructed by physical networks,which undergoes the serious thermal decay on mechanical properties at high temperature.Herein,a physically cross-linked PU with a unique thermal stiffening behavior has been developed by incorporating B–N coordination with reversible B–O bonds.The B–N coordination can significantly improve the mechanical properties of the PU.The reversible B–O bonds(temperature dependent reversible transformation between B–OH and B–O–B)are conducive to constructing more multicoordination macromolecular crosslinking points and more stable B–N coordination bonds at high temperature,endowing the PU with the special thermal stiffening behavior for the first time.Such thermal stiffening behavior compensates for the bond breakage and the network destruction caused by heat,significantly expands the rubbery plateau and delays the entire chain motion of the thermoplastic PU.As a result,the terminal flow occurs at a higher temperature up to 200°C.The modulus retention ratio of the materials is up to 87%even at 145oC,which is much higher than that of the existing PU elastomer with the physical network and even some covalent cross-link PU.Simultaneously,the physical network ensures the recyclability of the PU,and the thermal stiffening behavior is still obtained in recycled PU.This work provides a simple strategy to impart thermal stiffening behavior to the physically crosslinked PU,thereby significantly extending the operating temperature range of thermoplastic PU,which can potentially expand the scopes of PU in applications under harsh conditions.热软化在物理网络中是难以避免的,聚氨酯(PU)作为一种由物理网络构成的典型商用材料,在高温下其力学性能会发生严重的衰减.在本论文中,我们通过引入的可逆B–O键与B–N配位的相互作用,开发了一种具有独特热增强行为的物理交联PU.其中B–N配位提高了PU的力学性能.在高温下,可逆的B–O键(B–OH和B–O–B之间依赖温度的可逆转变)会构建更多的多配位大分子交联点和更稳定的B–N配位,这一机制首次赋予了PU热增强行为.当温度升高至100°C后,材料的储能模量和断裂应力都随着温度升高而增加,这种热增强行为补偿了高温下键的断裂和网络的破坏,显著地扩展了热塑性PU的橡胶平台并延迟其整链运动,使其末端松弛发生在更高的温度下.即便温度达到145°C,材料的模量保留率也高达87%,远高于现有的物理交联甚至一些共价交联的PU弹性体.同时,物理网络保证了PU的可回收性,并且在多次回收中,PU仍然具有优异的热增强行为.这项工作提供了一种简单且有效的策略来赋予物理交联PU显著的热增强行为,从而大大扩宽了热塑性PU的使用温度范围,这将扩展PU在恶劣条件下的应用.

关 键 词：RECYCLABLE POLYURETHANE B-N coordination reversible B-O bonds thermal stiffening behavior 

分 类 号：TQ334.1[化学工程—橡胶工业] O641.4[理学—物理化学]