Synthesis of novel biobased polyimides derived from isomannide with good optical transparency, solubility and thermal stability

Abstract

Novel biobased polyimides (PIs) with good optical transparency and comprehensive properties were synthesized from isomannide-derived diamine and dianhydride monomers. Three kinds of diamines including 2,5-diamino-2,5-dideoxy-1,4:3,6-dianhydroiditol (M1), 1,4:3,6-dianhydro-2,5-di-O-(4-aminophenyl)-D-mannitol (M2), and 1,4:3,6-dianhydro-2,5-di-O-(2-trifluoromethyl-4-aminophenyl)-D-mannitol (M3), as well as 1,4:3,6-dianhydro-2,5-di-O-(3,4-dicarboxyphenyl)-D-mannitol dianhydride (M4), were prepared based on isomannide. These diamines M1–M3 were reacted with M4 and a commercial dianhydride, 4,4′-oxydiphthalic anhydride (ODPA), via a two-step polymerization method, respectively, to yield a series of biobased PI films, PI-1 to PI-6. The resultant PIs had a high content of biomass up to 48 wt%, and they can be readily soluble in various non-proton polar solvents at room temperature. Most of the biobased PIs showed good optical transparency (transmittances at 450 nm over than 80%), along with a cut-off wavelength of 343–364 nm. Furthermore, due to the existence of rigid alicyclic isomannide among the polymeric backbone, biobased PIs maintained fairly high thermal stability with a glass transition temperature of 227–264 °C, and temperature at 5% weight loss over 400 °C in nitrogen. Meanwhile, these PIs exhibited outstanding mechanical properties with tensile strengths greater than 90 MPa and elongation at break higher than 6.0%. It was also found that the biobased PI series with alicyclic M1 possessed higher thermal stability than PIs with semi-aromatic diamines M2 and M3. Thereof, the introduction of biomass building blocks into PIs can offer a great opportunity to develop new sustainable materials with high performance for microelectronic and optoelectronic applications.