The highly crosslinked dimethacrylic/divinylbenzene copolymers Characterization and thermal studies

The series of highly crosslinked, hydrophilic stable spherical microspheres based on the new aromatic tetrafunctional methacrylate monomers and divinylbenzene (DVB) were prepared by emulsion-suspension polymerization in the presence of pore-forming diluents (toluene/decan-1-ol). The new monomers were generated by treatment of epoxides derived from various diphenols: naphthalene-2,7-diol (NAF-2,7) naphthalene-2,3-diol (NAF-2,3), bis(4-hydroxyphenyl)methanone (BEP) or 4,4'-thiodiphenol (BES), and epichlorohydrin with methacrylic acid. The copolymerization process of new methacrylate monomers with DVB was carried out at constant mole ratio of methacrylate monomers: DVB (1:1) and constant volume ratio of pore-forming diluents to monomers (1:1) using alpha,alpha'-azoisobisbutyronitrile (AIBN) as initiator. The effect of the structure of new methacrylate monomers on the surface appearance, porous structure, swelling behavior in polar, and non-polar diluents as well as thermal properties of obtained copolymer beads was evaluated. The obtained results confirmed that the monomer's structure considerably influenced on the microspheres characteristic. In general, higher swelling properties of dimethacrylic/divinylbenzene copolymers were observed in polar diluents due to the presence of polar groups: hydroxyl and ester groups in copolymer's structure. Moreover, both the swelling properties of dimethacrylic/divinylbenzene copolymers as well as thermal properties studied by DSC and TG analysis confirmed that diacrylic/divinylbenzene copolymers described in previous article were more crosslinked compared to those actually studied. It was attributed to the presence of additional groups (methyl groups) in dimethacrylic/divinylbenzene copolymer's structure and thus producing of more flexible polymeric networks due to the steric hindrance.