Diels–Alder Reaction as a Tool to Modify the Surface of Polymeric Microspheres

The study describes the synthesis of glycidyl methacrylate microspheres cross-linked with ethylene glycol dimethacrylate. With the use of suspension–emulsion polymerization, microspheres with different degrees of cross-linking were prepared. Their chemical modification involved several steps: at the beginning, the epoxide ring was opened using sodium cyclopentadienide; in the next step, materials with grafted cyclopentadiene fragments were then subjected to Diels–Alder reaction with maleic anhydride; in the last step, the anhydride groups were turned into carboxylic groups. To confirm the attachment of cyclopentadiene to the microspheres surface, the material obtained was treated with fluorescence marker N-(1-pyrene) maleimide. The resulting material has fluorescent properties in the UV wavelength of 366 nm. Moreover, to confirm the chemical structure of modified materials, attenuated total reflection-Fourier transform infrared spectroscopy analysis was performed. Thermal stability in inert atmosphere of prepared microspheres was determined. It was found that chemical modification of the microspheres surface improves their thermal resistance. On the basis of this study, it can be assumed that the Diels–Alder reaction is an expedient tool to obtain microspheres having carboxyl and hydroxyl groups, which can be an interesting option as stationary phases in chromatography.