Abstract. This work illustrates that macrocycles can be used as crosslinking agents for curing epoxy resins, provided that they have appropriate organic functionalities. As macrocycles can complex metal ions in their structure, this curing reaction allows for the introduction of that metal ion into the resin network. As a result, some characteristic physical properties of the metallomacrocycle could be transferred to the new material. The bisphenol A diglycidyl ether (BADGE, n = 0) and hemin (a protoporphyrin IX containing the Fe(III) ion, and an additional chloride ligand) have been chosen. The new material has been characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), Transmission Electron Microscopy (TEM), and magnetic susceptibility measurements). Fe(III) remains in the high-spin state during the curing process and, consequently, the final material exhibits the magnetic characteristics of hemin. The loss of the chlorine atom ligand during the cure of the resin allows that Fe(III) can act as Lewis acid, catalyzing the crosslinking reactions. At high BADGE n = 0/hemin ratios, the formation of ether and ester bonds occurs simultaneously during the process.

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Different crown ethers (4-aminobenzo-15-crown-5 (4-aminobenzo-15-C5), 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (diaza-18-crown-6), tetraazacyclododecane-1,4,7,10-tetraacetic acid (H 4 DOTA) and tetraazacyclododecane-1,4,7,10tetraacetamide (H 2 ODDA)) were used as curing agent for bisphenol A diglycidyl ether (BADGE, n = 0). The maximum enthalpy change for all systems except that formed by the epoxy resin with H 4 DOTA corresponds to a stoichiometric ratio, since from this value the reaction enthalpies decrease when the proportion of epoxy increases. Heteropolymerization reaction occurs in all the crown ethers. Etherification reactions occur at temperatures much lower (30 ∘ C less) than for the porphyrin systems studied in which a second signal appears at 300 ∘ C. The etherification is evidenced by a slight shoulder in the thermograms for H 4 DOTA and H 2 ODDA. The systems BADGE (n = 0)/4-aminobenzo-15-C5 and BADGE (n = 0)/diaza-18-crown-6 improve the thermal stability of the epoxy resin by 30 ∘ C approximately while the improvement for BADGE (n = 0)/H 4 DOTA and BADGE (n = 0)/H 2 ODDA is about 60 ∘ C. RESULTS AND DISCUSSIONExamples of the dynamic experiments of the polymer (BADGE, n = 0)/crown ether are shown in Fig. 2.

xTwo similar macrocycles protoporphyrin IX and zinc protoporphyrin IX (ZPP) have been used as cross-linking agents for curing the epoxy resin of bisphenol A diglycidyl ether (BADGE, n = 0). The enthalpies and the activation energies of the esterification reaction of the 2 systems are very close to each other. However, the temperature of the minimum in the differential scanning calorimetry thermogram is 38°C lower for BADGE (n = 0)/ZPP, thus requiring a less energy expenditure for curing the system. By the contrary, the enthalpy and activation energies for the etherification reaction are lower and higher, respectively, for BADGE (n = 0)/ZPP suggesting that the zinc ion affects it, although the involved mechanism is unknown. KEYWORDSepoxy resin, protoporphyrin IX, zinc protoporphyrin IX, Zn ion

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