Novel porphyrin-containing hydrogels obtained by frontal polymerization: Synthesis, characterization and optical properties

Frontal polymerization was successfully used to prepare two series of copolymers from a tetraphenylporphyrin-containing monomer (TPP-TEG-MA) and poly(ethylene glycol) methyl ether acrylate (PEGMA) or di(ethylene glycol) methyl ether methacrylate (DEGMA). Tricaprylmethylammonium (Aliquat) persulfate (APSO) was used as radical initiator to obtain highly fluorescent hydrogels with different chromophore contents. The obtained hydrogels, PEGTPP and DEGTPP series, were characterized by FT-IR spectroscopy, and the successful incorporation of TPP-TEG-MA monomer into the polymer backbone was observed. Their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The swelling behavior of the obtained hydrogels was measured at 25 °C and pH = 7. The swelling ratio increased until equilibrium was reached after 24 h. Furthermore, the pH and temperature responses of the obtained hydrogels were measured. The optical properties of these materials were studied by absorption and fluorescence spectroscopies. They exhibited an absorption band at 418 nm (Soret band) and an emission band at 653 nm, which are typical of the porphyrin moiety.