Preparation and Characterization of Electrospun Fluoro-Containing Poly(imide-benzoxazole) Nano-Fibrous Membranes with Low Dielectric Constants and High Thermal Stability.

Meng-Ge Huangfu,Yuan-Cheng An,Yan Zhang,Deng-Xiong Shen,Yan-Jiang Jia,Xin-Ying Wei,Jin-Gang Liu,Xin-Xin Zhi

doi:10.3390/nano11020537

Abstract

The rapid development of advanced high-frequency mobile communication techniques has advanced urgent requirements for polymer materials with high-temperature resistance and good dielectric properties, including low dielectric constants (low-Dk) and low dielectric dissipation factors (low-Df). The relatively poor dielectric properties of common polymer candidates, such as standard polyimides (PIs) greatly limited their application in high-frequency areas. In the current work, benzoxazole units were successfully incorporated into the molecular structures of the fluoro-containing PIs to afford the poly(imide-benzoxazole) (PIBO) nano-fibrous membranes (NFMs) via electrospinning fabrication. First, the PI NFMs were prepared by the electrospinning procedure from organo-soluble PI resins derived from 2,2′-bis(3,4-dicarboxy-phenyl)hexafluoropropane dianhydride (6FDA) and aromatic diamines containing ortho-hydroxy-substituted benzamide units, including 2,2-bis[3-(4-aminobenzamide)-4-hydroxylphenyl]hexafluoropropane (p6FAHP) and 2,2-bis[3-(3-aminobenzamide)-4-hydroxyphenyl]hexafluoropropane (m6FAHP). Then, the PI NFMs were thermally dehydrated at 350 °C in nitrogen to afford the PIBO NFMs. The average fiber diameters (dav) for the PIBO NFMs were 1225 nm for PIBO-1 derived from PI-1 (6FDA-p6FAHP) precursor and 816 nm for PIBO-2 derived from PI-2 (6FDA-m6FAHP). The derived PIBO NFMs showed good thermal stability with the glass transition temperatures (Tgs) over 310 °C and the 5% weight loss temperatures (T5%) higher than 500 °C in nitrogen. The PIBO NFMs showed low dielectric features with the Dk value of 1.64 for PIBO-1 and 1.82 for PIBO-2 at the frequency of 1 MHz, respectively. The Df values were in the range of 0.010~0.018 for the PIBO NFMs.

Highlights

The rapid development of telecommunication techniques has witnessed the start of fifth-generation (5G) era in recent years [1]
P6FAHP and m6FAHP were synthesized by a two-step procedure shown in Figure 2. p-Nitrobenzoyl chloride or m-nitrobenzoyl chloride were first reacted with 6FAP at low temperature in the solvent to form the dinitro compounds. pyridine was used as the absorbent of the produced hydrogen chloride (HCl) by-products
HCl was removed from the reaction in the form of pyridine hydrochloride

Summary

Introduction

The rapid development of telecommunication techniques has witnessed the start of fifth-generation (5G) era in recent years [1]. One of the most extraordinary features of 5G communication is the high-frequency transmission of signals in hardware [2]. This characteristic makes it very important to achieve low-loss and low-delay signals transmission [3]. The signal delay caused by various components in 5G hardware seems to be more serious with increasing frequency. It has been well established that the signal delay is closed with the dielectric constants of the materials that the signals penetrate [4,5,6]. The lower the dielectric constant (Dk ) and dielectric dissipation factor (Df ) of the hardware dielectric materials, the smaller the delay of the signal transmission [7].

Methods

Results

Conclusion