Synthesis and characterization of high fluorine‐containing polyimides with low‐dielectric constant

Abstract

Aromatic polyimides (PI) with low‐dielectric constant are becoming more and more important with the continuous development of high‐speed communication technology. Herein, high fluorine‐containing PI with low‐dielectric constant was prepared. First, a novel aromatic diamine monomer 4,4′‐(3,3′‐bis[trifluoromethyl]biphenyl‐4,4′‐diyl)bis(oxy)bis(3‐[trifluoromethyl]aniline) bearing multi‐trifluoromethyl groups (12FDA) was synthesized and characterized. Subsequently, a series of PI with high‐fluorine content (HFPI) were obtained by two‐step polymerization of 12FDA with three commercial dianhydrides. The polymer films cured at a maximum temperature of 310°C showed excellent thermal and mechanical properties with high‐glass transition temperatures (>250°C) and high‐storage modulus (> = 2.0 GPa). The 5% weight loss temperatures of HFPIs were all above 500°C, which indicated that HFPIs exhibited excellent thermostability. Meanwhile, HFPI exhibited low‐water absorption (<0.3%) and low‐dielectric constant (2.40–2.68 at 1 MHz). The excellent thermal, mechanical, and electrical properties make it a promising dielectric material in electronics and communication industry.

New polyimides containing methyl benzamidobenzoate or dimethyl benzamidoisophthalate as bulky pendant groups. Effects on solubility, thermal and gas transport properties

“…[6][7][8] Despite their outstanding properties, most PIs are usually insoluble in most common organic solvents, which negatively impacts the process ability of these materials. The poor solubility of polyimides is related to the charge-transfer complexes formed due to the proximity between the donor and acceptor fragments present in the imide group, 9 in addition to the π-π stacking interactions generated by the aromatic rings along the main chain of the polymer. 10 Many efforts have been made to improve the solubility of PIs, focusing on modifying the structural characteristics of the monomers to reduce the interactions between the polymer chains.…”

Composite films with low dielectric constant and dielectric loss factor at high frequency prepared from polyimide and polytetrafluoroethylene

“…It is mainly due to the fact that the trifluoromethyl group (‐CF 3 ) in the molecular structure not only increases the free volume and hinders the dipole orientation process, but also largely reduces the polarization rate due to its extremely electronegative nature. [ 14 ] The dielectric properties of the PI were greatly improved after the addition of PTFE. The D f of the PI/PTFE films was reduced by up to 20% and the PI/PTFE‐40 shows the lowest D k and D f ( D k = 2.42, D f = 0.0041) with the highest PTFE content of 40 wt%.…”

“…[8][9][10] In general, D k is mainly determined by the density of molecular polarizable components and the relationship of molecular polarization and is explained clearly by the Clausius-Mossotti equation. [11][12][13] Several PI films with low D k have been synthesized by introducing strongly electronegative groups, [14][15][16] and large side-group structures. [17,18] However, it is difficult to realize industrial production because of its expensive cost and cumbersome process.…”

Low Dielectric Properties and Transmission Loss of Polyimide/Organically Modified Hollow Silica Nanofiber Composites

“…However, the dielectric constant of normal PI is just in the range from 3.1~3.5 [ 5 ], which is apparently incapable of meeting their requirements for highly integrated electronic components and requires a lower dielectric constant of substrate materials [ 6 ]. In order to reduce the dielectric constant from normal PI, different approaches have been applied and reported by the synthesis of various chemical structures [ 5 , 7 , 8 , 9 ] and the organic–inorganic composites [ 2 , 10 , 11 , 12 , 13 ]. For example, Kuo et al [ 7 ] synthesized a series of PI with exotic functional groups including ether, fluorine, ester, amide, ketone, sulfide, sulfone, and alkane groups and proposed that the highly correlated relationship between the dielectric constant of ether and fluorine-based PIs to the fluorine content.…”