Phase separation in liquid crystalline mesophases of [Co(H2O)6]X2:P65 systems (X = NO3-, Cl-, or ClO4-)

被引:16
作者
Albayrak, Cemal [1 ]
Gulten, Gulcin [1 ]
Dag, Omer [1 ]
机构
[1] Bilkent Univ, Lab Adv Funct Mat, Dept Chem, TR-06800 Ankara, Turkey
关键词
D O I
10.1021/la0622119
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Transition-metal aqua complex salts [M(H2O)(6)]X-2 (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)]X-2: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)]X-2: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)]X-2:P65 systems can also be eliminated by keeping the mesophase under a N-2 atmosphere.
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收藏
页码:855 / 860
页数:6
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