Soluble polyimides containing 1,4:3,6-dianhydro-d-glucidol and fluorinated units: Preparation, characterization, optical, and dielectric properties

摘要

Aiming to develop soluble and colorless polyimides, two novel diamines, 2,5-bis(2-trifluoromethyl-4-amino-phenoxy)-1,4:3,6-dianhydrosorbitol (2a) and 2,5-bis(2-methyl-4-amino-phenoxy)-1,4:3,6-dianhydrosorbitol (2b), were designed and synthesized by the reduction of corresponding dinitro monomer which was obtained via solvent-free melt heating method. Polyimides (PI-(1-5)) containing 1,4:3,6-dianhydro-d-glucidol fragments were prepared from 2a and five kinds of common dianhydrides and PI-6 was synthesized from 2b and 4,4-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) via a two-step thermal imidization. All the polyimides were readily soluble in common polar solvents and could afford flexible, tough, and transparent films with transparency as high as 87% at 450 nm. Meanwhile, PI-(1-6) exhibited unexpectedly low dielectric constants of 2.02-2.52 at 1 MHz. In addition, analogs PI-7 derived from 2,5-bis(4-amino-phenoxy)-1,4:3,6-dianhydrosorbitol (2c) and 6FDA and PI-8 derived from 4,4-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (2d) and 6FDA were also obtained via a two-step thermal imidization for comparision with PI-(1-6) on aspects of thermal, mechnical, optical, electrical, and morphological properties. The structure-property relationships of PI-(1-8) were discussed in detail. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3253-3265