Coloration of Ethyleneamine-Diacrylate-Based Porous Polymer-Toluene Systems Induced by the Christiansen Effect: Color Control by the Molecular Design of the Polymer Networks

The aza-Michael addition reaction of ethyleneamine, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), or pentaethylenehexamine (PEHA) with poly-(ethylene glycol) diacrylate (PEGDA) in ethanol at 20 °C yielded the corresponding porous polymers. The surface morphology of the porous polymers was composed of connected particles or cocontinuous monolithic structure, which were induced by phase separation. The TETA- and TEPA-PEGDA porous polymers turned half transparent and colored in toluene through the Christiansen effect. The transmission peak top (λ_max) of the porous polymer-toluene system showed a blue shift with an increase in the observation temperature, and the complementary colors of the transmission peak were observed as the scattered light. The porous polymers based on TEPA/PEGDA/mono- or diacrylate with ethylene glycol or propylene glycol linkage and TEPA/diacrylate systems in toluene also showed the coloration. These polymers showed blue- or red-shifts of λ_max depending on the molecular structure of mono- or diacrylate monomers. Effects of the molecular structure of the polymer networks on the coloration behavior were discussed.