| 17209644 |
Albayrak C, Gulten G, Dag O: Phase separation in liquid crystalline mesophases of [Co (H2O) 6] X2:P65 Systems (X = NO3-, Cl-, or ClO4-). Langmuir. 2007 Jan 16;23(2):855-60.
Transition-metal aqua complex salts [M (H2O) 6] X2 (where M is Mn (II), Co (II), Ni (II), Zn (II), or Cd (II) and X is NO3-, Cl-, or ClO4-) can be dissolved in triblock poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) copolymers (Pluronics, such as P65) to form homogeneous liquid crystalline (LC) mesophases. However, the [Co (H2O) 6] X2:P65 LC mesophases slowly undergo phase separation into a disordered ion-free phase and an ordered ion-rich LC mesophase. The phase separation also takes place in the two-salt systems [Co (H2O) 6](NO3):[Co (H2O) 6](ClO4) 2:P65 in which the ion-free disordered domains separate out from the initially ordered homogeneous mesophase. The phase separation results in a physical mixture of a hexagonal nitrate-rich and cubic perchlorate-rich LC and disordered ion-free domains in the mixed salt systems. The driving force in the phase separation in the [Co (H2O) 6] X2:P65 system is Co (II)-catalyzed aerobic oxidation of P65 into ester and/or other oxidation products. The separation of ions in the [Co (H2O) 6](NO3) 2:[Co (H2O) 6](ClO4) 2:P65 system is related to the mesostructures of the two-salt systems that are different, hexagonal in the [Co (H2O) 6](NO3) 2:P65 system and cubic in the [Co (H2O) 6](ClO4) 2:P65 system. There is no visible phase separation in the other transition-metal salt:P65 systems. The phase separation in the [Co (H2O) 6] X2:P65 systems can also be eliminated by keeping the mesophase under a N2 atmosphere. |
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