Soluble Biobased Polyimides from Diaminotruxinic Acid with Unique Bending Angles

Biobased diamines with unique bending angles, β- and δ-type truxinic acids, were prepared from functionalized 4-nitrocinnamic acid derivatives via solid-state photodimerization and further chemical modification. The obtained diamines were polymerized with tetracarboxylic acid dianhydrides to produce soluble polyimides via chemical imidization at a high efficiency. The obtained δ-type-based polyimides exhibited a high thermostability at 10% weight loss temperature of ∼415 °C and good solubility in organic solvents. Most of the polyimides were soluble in chloroform and dichloromethane, as well as polar organic solvents. Tensile test results showed that biopolyimide films from cyclobutanetetracarboxylic dianhydride exhibited ∼10.2% elongation at break, indicating high flexibility.