Aiming to develop soluble and colorless polyimides, two novel diamines, 2,5-bis(2-trifluoromethyl-4-aminophenoxy)-1,4:3,6-dianhydrosorbitol (2a) and 2,5-bis(2-methyl-4amino-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-Dglucidol fragments were prepared from 2a and five kinds of common dianhydrides and PI-6 was synthesized from 2b and 4,4 0 -(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 0 -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.
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