Porous polymaleimide networks

Porous network structures were prepared by in situ polymerisation of a mixture of N-phenylmaleimide and 1, 1'-(methylenedi-4,1-plienylene)bismaleimide (95:5 w/w) in poly(vinylidene difluoride-co-hexafluoropropylene) (PVDH). The mixture of the maleimide monomers was found to form thermoreversible gels with PVDH. Thermodynamic analysis of the gelation process using calorimetry data indicated the formation of complexes of N-phenylmaleimide and vinylidene difluoride repeat units with a molar ratio of 1:2, respectively. PVDH formed optically clear solutions in the mixture above the gelation temperature, observed at 80-120 degreesC depending on composition. Polymerisation of the maleimides was induced by increasing the temperature to 250 degreesC. During polymerisation, the resulting polymaleimide phase separated from the PVDH melt. A morphological study by microscopy revealed that blends with 80 wt% PVDH contained continuous networks of crosslinked polymaleimide. The porous networks were collected after removing the PVDH by solvent extraction. Thermogravimetrical analysis of the polymaleimide networks under N-2 atmosphere showed that the onset of weight loss occurred at 380 degreesC. These networks may thus be used to prepare thermally stable membranes.