Molecular Chain Flexibility and Dielectric Loss at High-Frequency:Impact of Ester Bond Arrangement in Poly(ester imide)s  

作　　者：Ya-Dong Li Hong Li Lu-Kun Feng Feng Bao Ming-Liang Wang Cai-Zhen Zhu Zhao-Hui Zheng Xiao-Bin Ding Jian Xu 

机构地区：[1]Chengdu Institute of Organic Chemistry,Chinese Academy of Sciences,Chengdu 610041,China [2]University of Chinese Academy of Sciences,Beijing 100081,China [3]Institute of Low-Dimensional Materials Genome Initiative,College of Chemistry and Environmental Engineering,Shenzhen University,Shenzhen 518060,China

出　　处：《Chinese Journal of Polymer Science》2024年第8期1122-1133,共12页高分子科学（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(No.52303010);Key-Area Research and Development Program of Guangdong province(No.2019B010941001);Key Technology of Liquid Crystal Polymer Material for 5G/6G High Frequency Communication(No.JSGGZD20220822095201003);Songshan Lake Materials Laboratory(No.2021SLABFK01);the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110143)。

摘　　要：The evolution of high-frequency communication has accentuated the significance of controlling dielectric properties in polymer media.Traditionally,it has been theorized that rigid molecular chains lead to lower dielectric loss.However,the validity of this proposition at high frequencies remains uncertain.To scrutinize the correlation between chain flexibility and dielectric properties,we synthesized six poly(ester imide)s(PEIs)with systematically varied molecular chain flexibilities by modifying the ester's substitution on the aromatic ring.The introduction of ester bonds bestowed all PEI films with a low dielectric dissipation factor(D_(f)),ranging from 0.0021 to 0.0038 at 10 GHz in dry conditions.The dry D_(f)displayed a pattern consistent with volume polarizability(P/V).Unexpectedly,PI-mmm-T,featu ring the most flexible molecular chain,exhibited the lowest dielectric loss under both dry(0.0021@10 GHz)and hygroscopic(0.0029@10 GHz)conditions.Furthermore,the observed increase in D_(f)after humidity absorption suggests that the high dielectric loss of PEI in applications may be attributed to its hygroscopic nature.Molecular simulations and characterization of the aggregation structure revealed that the smaller cavities within flexible molecular chains,after close stacking,impede the entry of water molecules.Despite sacrificing high-temperature resistance,the precursor exhibited enhanced solubility properties and could be processed into high-quality films.Our research unveils new insights into the relationship between flexibility and highfrequency dielectric loss,offering innovative perspectives on synthesizing aromatic polymers with exceptional dielectric properties.

关 键 词：5G communications Poly(ester imide)s Molecular chain flexibility Dielectric properties Humidity absorption 

分 类 号：TQ323.7[化学工程—合成树脂塑料工业]