Thermo-reversible Diels-Alder polymerization of difurfurylidene diglycerol and bismaleimide

Difurfurylidene diglycerol (DFDG) was synthesized by the acetalization reaction of furfural and diglycerol, both of which can be derived from renewable resources. The H-1 and C-13 NMR analyses revealed that DFDG is a mixture of stereoisomers. Diels-Alder (DA) polymerization of equimolar amounts of DFDG and 4,4-bismaleimidodiphenylmethane (BMI) at 60 degrees C for 48 h in chloroform afforded a bio-based linear polyimide (DFDG-BMI) with M-w of 5400. Prolonged reaction time resulted in a lowering of molecular weight and an increase of exo/endo DA adduct ratio. The M-w of the polyimide obtained by the reprecipitation of DFDG-BMI (pDFDG-BMI) was 7900. The X-ray diffraction and polarized optical microscopic analyses revealed that pDFDG-BMI is a crystalline polyimide. The differential thermal analysis revealed that pDFDG-BMI had a melting temperature at 126 degrees C, and broad endothermic peaks at around 140-170 degrees C due to retro DA reaction. The retro DA depolymerization of pDFDG-BMI in N,N-dimethylformamide smoothly proceeded at around 100-120 degrees C to regenerate the corresponding monomers, as is obvious from the gel permeation chromatographic and H-1 NMR spectral analyses. (C) 2014 Elsevier Ltd. All rights reserved.