ORIGINAL PAPER New polyimide-based porous crosslinked beads by suspension polymerization: physical and chemical factors affecting their morphology C. Hulubei & C. D. Vlad & I. Stoica & D. Popovici & G. Lisa & S. L. Nica & A. I. Barzic Received: 6 January 2014 /Accepted: 16 June 2014 /Published online: 21 August 2014 # Springer Science+Business Media Dordrecht 2014 Abstract 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 400ºC, having a pore volume of 1.28 mL/g, a surface area of 74.20 m2/g and enhanced swelling properties. Keywords Polyimides . Alicyclic . Suspension polymerization . Crosslinked porous beads Introduction Nowadays, the development of new polymeric materials with improved properties still represents a major objective both in synthesis and in the quest of new applications. The porous crosslinked polymer particles [1, 2], especially the ones that are spherical in shape, classified as macro- meso- and microporous, depending on the pore size (>50 nm, 50÷ 2 nm and <2 nm, respectively) have received great attention because of their various applications including catalytic reaction engineering, separation processes, consumer products (i.e., water softeners and defuming agents), biomedical devices, coating additives or controlled release reservoirs [3–5]. Techniques for the preparation of macroporous polymers were developed almost 40 years ago [6]. From these, suspension polymerization method [7, 8] has generally been used in polymer industry for the prep- aration of robust macroporous (co) polymer networks in beads form (in the micron-size range: 5÷1,000 μm), particularly used as chromatographic separation media, precursors for ion exchange resins, supports for enzyme immobilization and other technological applications [1, 9–11]. Crosslinked polymer beads, obtained by radical polymeri- zation reaction of multifunctional monomers or polymers containing polymerizable groups, are very interesting com- plex structures as a consequence of the kinetic reaction mech- anism and the spatial correlation between the resulting poly- meric chains [12]. The final (co) polymers properties can be changed by changing the composition of the reacting mix- tures, so that the monomers structure and their reactivity become key-factors in the morphologies optimization for spe- cific applications. The most studied monomers used in the polymeric microspheres synthesis are those nonpolar like styrene (ST) and divinylbenzene (DVB) or medium polar such as methyl methacrylate compounds with reactive groups (MMA) [13] the monomers number with functional surface groups being however limited [14]. Paper dedicated to the 65th anniversary of “Petru Poni” Institute of Macromolecular Chemistry of Romanian Academy, Iasi, Romania. C. Hulubei (*) : C. D. Vlad : I. Stoica : D. Popovici : S. L. Nica : A. I. Barzic “Petru Poni” Institute of Macromolecular Chemistry, 41A Grigore Ghica Voda Alley, Iasi 700487, Romania e-mail: hulubei@icmpp.ro G. Lisa “Gheorghe Asachi” Faculty of Chemical Engineering and Environmental Protection, Technical University, 73 Dimitrie Mangeron Bdv., Iasi 700050, Romania J Polym Res (2014) 21:514 DOI 10.1007/s10965-014-0514-4