Under two-liquid conditions, the third phase formed by linear-polystyrene-based cationic ionomers and the corresponding single-network ionomer gels absorbed the soluble quaternary salts either from the oil phase or from the aqueous solution. Polystyrene-based IPN gels, in which one network contained quaternary salts and another benzyl chlorides, were compared in terms of the feasibility of esterification of the chloromethyl groups in addition to the triphase catalysis (TPC) activities. IPN gels afforded not only very poor TPC activities but also slow esterification. Single-network gels, on the other hand, showed high TPC activities and high esterification rates. When decane was used as the oil, the TPC activity was increased, while the esterification became slower.