Abstract: TX-100/n-hexanol/water/cyclohexane inverse microemulsions have been used to entrap tetrakis(4-sulfonatophenyl)porphyrin (TPPS). The aggregation behaviors of TPPS in the inner phase of nonionic W/O inverse have been investigated on changing pH, size of the microemulsions water pool and the concentration of porphyrin. The apparent pKa of TPPS in microemulsions have been found to be much lower than that in open aqueous solution, and exhibit a decrease on decreasing the water pool dimension. Deprotonized TPPS was prevalently presented when pH > pKa. While J-aggregates and protonized TPPS are the main species existed when pH < pKa, and more protonized TPPS self-assemble into J-aggregates on increasing the concentration of TPPS. At fixed pH, the deprotonized TPPS tend to become protonized and self-assemble into J-aggregates on increasing the inner water pool dimension.

Key words: TPPS, soft microconfinement, nonionic surfactant, inverse microemulsions