Synthesis and Phase Behavior of New Amphiphilic PEG-Based Triblock Copolymers as Gelling Agents for Lamellar Liquid Crystalline Phases

We report the first evidence of the potential of new amphiphilic ABA-triblock copolymers as gelling agents for lamellar liquid crystalline LR phases. Recently, we described a new type of lamellar hydrogels which are not based on a polymer network swollen in water but are obtained by the addition of small amounts of a nonionic polymer surfactant to the fluid lamellar LR phase of the dimyristoyl- phosphatidyl-choline(DMPC)/pentanol/water system. In contrast with these previously reported gelling agents which were all AB-diblock copolymers, the novel ABA-triblock copolymers consist of double chain hydrophobic moieties (A) attached to each end of a poly(ethylene glycol) chain (B). The synthesis of these new macromolecules and their gelation properties are described. The comparison of these novel lamellar hydrogels with those based on the AB-diblock copolymers provides direct evidence for the existence of cross-bridging conformations of the ABA-triblock copolymers between adjacent membranes.