Browsing by Subject "C12EO10"

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    ItemOpen Access
    Investigation of two new lyotropic liquid crystalline systems : [Zn (formula) and [Zn (formula)
    (2008) Albayrak, Cemal
    The transition metal aqua complex salts (TMS) can be dissolved in oligo (ethylene oxide) type non-ionic surfactants (CnH2n+1(CH2CH2O)mOH, denoted as CnEOm) with very high salt/surfactant ratios to form lyotropic liquid crystalline (LLC) mesophases. In this study we show that addition of charged surfactants, such as cethyltrimethylammoniumbromide (CTAB) or sodiumdodecylsulfate (SDS) results a new type of LLC in which the solubility of the salts in the LC mesophase of TMS: C12EO10 is enhanced. The LC phase of a [Zn(H2O)6](NO3)2:C12EO10 is hexagonal between 1.2 and 3.2 and cubic (liquid like) above 3.2 salt/ C12EO10 mole ratios. Addition of CTAB or SDS increases the same salt/surfactant mole ratio to 8.0-9.0, which is a record salt amount for a lyotropic liquid crystalline system. The mixed surfactant mesophases have birefringent hexagonal mesophase between 2.0 and 8.0 salt/C12EO10 mole ratios The new mixed surfactant systems can also accomodate high TMSs in the presence of excessive amounts of water (35.0 water:C12EO10 mole ratio). Both systems have similar thermal properties. Izotropisation Temperature (IT) values of the new systems go down with increasing salt and charged surfactant concentrations. The mesophases are stable at high salt concentrations in the presence of high CTAB or SDS concentration in the expense of the stability of the LLC mesophase. The IT values changes from around 80o C down to 32o C with increasing composition of the LLC mesophase. The new mesophase have 2D or 3D hexagonal structure that responds to water content of the phase. A 3D hexagonal phase transforms to 2D hexagonal phase with the evaporation of excess water in both [Zn(H2O)6](NO3)2:C12EO10-CTAB-H2O and [Zn(H2O)6](NO3)2:C12EO10-SDS-H2O systems. The new mesophases were investigated using POM (Polarised optical microscope), and a hot stage under the POM, XRD (X-ray Diffraction), FT-IR (Fourier Transform Infrared Spectroscopy) and Raman techniques. These new LLC systems are good candidates for metal containing mesostructured material synthesis due to their high salt content.
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    ItemOpen Access
    The role of charged surfactants in the thermal and structural properties of lyotropic liquid crystalline mesophases of [Zn(H2O)6](NO3)2-CnEOm-H2O
    (2010) Albayrak, C.; Soylu, A. M.; Dag, Ö.
    The mixtures of [Zn(H2O)6](NO3)2 salt, 10-lauryl ether (C12H25(OCH2CH2)10OH, represented as C12EO10), a charged surfactant (cetyltrimethylammonium bromide, C16H33N(CH3)3Br, represented as CTAB or sodium dodecylsulfate, C12H25OSO3Na, SDS) and water form lyotropic liquid crystalline mesophases (LLCM). This assembly accommodates up to 8.0 Zn(II) ions (corresponds to about 80% w/w salt/(salt + C12EO10)) for each C12EO10 in the presence of a 1.0 CTAB (or 0.5 SDS) and 3.5 H2O in its LC phase. The salt concentration can be increased by increasing charged surfactant concentration of the media. Addition of charged surfactant to the [Zn(H2O)6](NO3)2–C12EO10 mesophase not only increases the salt content, it can also increase the water content of the media. The charged surfactant-C12EO10 (hydrophobic tail groups) and the surfactant (head groups)-salt ion (ion-pair, hydrogen-bonding) interactions stabilize the mesophases at such salt high and water concentrations. The presence of both Br and NO 3 ions influences the thermal and structural properties of the [Zn(H2O)6](NO3)2–C12EO10–CTAB(or SDS)–H2O LLCM, which have been investigated using XRD, POM (with a hot stage), FT-IR and Raman techniques.