Low dielectric constant polyimide nanomats by electrospinning

Abstract

The proper combination of material (i.e. fluorinated polyimides) and processing technique (electrospinning) could lead to the formation of polyimides with low dielectric constant, high thermo‐oxidative stability and glass transition temperature, and high hydrophobicity. The polyimides in this work were based on 4, 4‐bis [3′‐trifluoromethyl‐4′ (4′‐amino benzoxy) benzyl] biphenyl (Q) and various fluorinated and non‐fluorinated dianhydrides namely benzene‐1,2,4,5‐tetracarboxylic dianhydride, 3,3′,4,4′‐biphenyltetracarboxylic dianhydride, benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride, and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Processing of the polyimides was carried out in poly(amic acid) stage by two different methods—electrospinning and solution casting for comparison purposes. The processing of polyimides by electrospinning led to enhancement in mechanical properties (dianhydride‐structure dependent) and hydrophobicity without sacrificing thermo‐oxidative stability and glass transition temperatures significantly. Also, low dielectric constants (as low as 1.43) could be attained by suitable combination of dianhydride (6FDA) with 4, 4‐bis [3′‐trifluoromethyl‐4′ (4′‐amino benzoxy) benzyl] biphenyl diamine. Copyright © 2011 John Wiley & Sons, Ltd.

Thermal and dielectric properties of electrospun fiber membranes from polyimides with different structural units

“…The activity of electrons attracted by the fluorine are significantly reduced causing difficulty in polarization in 6FDA‐PI by external electric field and resulting in a decreased k value . This dielectric constant is lower than that of a electrospinning membrane reported by Chen F (ε = 1.42) . In the literature, the diamine used is 4,4‐bis [3′‐trifluoromethyl‐4′(4′‐amino benzoxy) benzyl] biphenyl(TFABB) which has relatively low reactivity due to the existence of fluorine groups in the unit compared to ODA used in the present work.…”

“…But the bands at 722 cm −1 in the FTIR spectra of PMDA‐PI [Figure (a)] and 6FDA‐PI [Figure (b)] corresponding to bending of CO groups left shift to 793 cm −1 as the benzene groups connecting the imide rings in PMDA‐PI and 6FDA‐PI are substituted by aliphatic rings in HPMDA‐PI [Figure (c)]. No absorption bands are found at 1720 cm −1 corresponding to CO stretching of carboxylic acid, indicating complete conversion of PAAs to PIs during imidization …”

“…Electrospinning is an easy performing method for preparation of fiber membranes. Some works for PI membranes based on electrospinning are reported, but the focus is mainly on preparation of uniform PI fibers as supports to form organic‐inorganic composites and on preparation of carbon fibers . Actually, the random intertexture of the fibers makes the as‐prepared membranes containing large number of pores which are useful of decreasing the dielectric constant .…”

“…report the dielectric properties of PMMA, PS, PVDF and PVP membranes by electrospinning . Chen et al . prepared PI fiber membrane with dielectric constant as low as 1.4 by electrospinning fluorine‐containing PAA.…”

Synthesis and Properties of New Fluorinated Polyimides Derived from an Unsymmetrical and Noncoplanar Diamine

“…Since being first reported in 1908 and followed by the introduction of the high molecular weight polymer in the 1950s, polyimides (PIs) have found a wide range of applications in advanced technologies because of their good mechanical properties, high thermal stability, and excellent electric properties. [1][2][3][4][5][6][7][8][9][10][11][12] However, most commercial PIs exhibit very limited solubilities and high melting points, thus presenting serious processing difficulties. Therefore, the soluble precursor polymers, poly(amic acid)s, are cast onto the substrates and thermally cyclodehydrated at elevated temperature to yield the insoluble PI films or coatings.…”