Vesicle-to-micelle transition in aqueous solutions of amphiphilic calixarene derivatives.
Structure and conformation of spontaneous self-assembled calix[8]arenes derivatives are studied by means of static and dynamic light scattering and electrophoretic mobility. These amphiphilic molecules are in the aggregated form in aqueous solution, in a wide range of pH; they take a vesicle structure in neutral and basic pH environment, but, in relatively strong acidic conditions (below pH=4.5), a transition from vesicle to micelle occurs. The structural change is driven by the surface charge density. At neutral pH calix[8]arenes take a negative surface charge, which prevents coagulation and ensures stability; at acidic pH the surface charge tend to become positive because of the protonation of the hydrophilic head. These pH-responsive aggregates, able to release an encapsulated hydrophilic guest, are promising systems for application as nanocarriers.
Micali
Norberto
N
CNR-Istituto per i Processi Chimico-Fisici, Via La Farina 237, I-98123, Messina, Italy. micali@me.cnr.it
Villari
Valentina
V
Consoli
Grazia M L
GM
Cunsolo
Francesca
F
Geraci
Corrada
C