Salt-induced reinforcement of anionic bio-polyureas with high transparency

Abstract

Bio-based polyureas (PUs) are prepared by the polyaddition of a multifunctional bio-photodimer 4,4'-diamino-α-truxillic acid having two amines and two carboxyls with an aromatic isocyanate comonomer. Weight average molecular weights of the PUs range from 2.4 × 105 to 2.5 × 105g mol−1 with a narrow distribution around 1.3. The 10% weight-loss temperature of the PUs ranges from 270 to 280 °C, whereas the softening temperature ranges between 180 and 210 °C. The PUs are well dissolved in polar organic solvents such as dimethylformamide and the cast film is prepared from these solutions. The films show high transparency and swell in the alkaline solution when the PU carboxyls are anionized. If metal nitrate salts are added to the films, mechanical properties are increased by the double interaction of the metal cation with carboxylate and nitrate with urea, which causes the films to change the color. Bio-based polyureas (PUs) are prepared by the polyaddition of a multifunctional bio-photodimer 4,4'-diamino-α-truxillic acid having two amines and two carboxyls with an aromatic isocyanate comonomer. The films of PUs show high transparency and swell in the alkaline solution when the PU carboxyls are anionized. If metal nitrate salts are added to the films, mechanical properties are increased by the double interaction of the metal cation with carboxylate and nitrate with urea, which causes the films to change the color.