New polyimide-based porous crosslinked beads by suspension polymerization: physical and chemical factors affecting their morphology

Synthesis of a new partial-alicyclic copolyimide based on bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BOCA) is presented. This polymer was used to obtain porous microspheres by suspension polymerization method. It is copolymerized with N, N’- 4, 4′- diphenylmethanebismaleimide in the presence of two pairs of porogens: 1-methyl-2-pyrrolidone/benzyl alcohol, and 1,4 Dioxane/benzyl alcohol. Influence of different factors, such as diluents composition or crosslinker concentration, on the resulting polymer beads morphology is studied. Various characteristcis including the specific and apparent densities, porosity, pore volume, surface area and mean pore diameter are analyzed. Thermal behavior and tendency to swell in different organic diluents for some chosen samples are also determined. The best polymer beads, obtained in a reaction system with a solubility parameter value of 23.45 MPa ½ and a crosslinker concentration of 40 %, are thermally stable above 400 ºC, having a pore volume of 1.28 mL/g, a surface area of 74.20 m2/g and enhanced swelling properties.