1 research outputs found
Mesogenic Structures, Lyotropic and Thermotropic Phase Transitions in Demethyl-Ionene Alkyl Sulfonate Complexes
Linear
[<i>B</i>,10]-polyamines [(CH<sub>2</sub>)<sub><i>B</i></sub>NÂ(CH<sub>3</sub>)Â(CH<sub>2</sub>)<sub>10</sub>NÂ(CH<sub>3</sub>)] were prepared (<i>B</i> = 3 or 6). Protonated
by stoichiometric amounts of <i>n</i>-alkylsulfonic acids,
they form demethyl-ionene sulfonate complexes, which proved thermally
stable up to 220 °C. Salt free complexes were investigated by
polarized microscopy, thermogravimetry, and X-ray diffraction. Except
the heptyl sulfonate, which crystallized, all complexes bearing longer
alkyl chains formed mesogenic phases. Being isotropic in dry state,
they became optically anisotropic when exposed to humidity due to
a lyotropic transition (mediated by the gas phase) to a hexagonal
phase, mostly. A cubic phase containing less water was also observed.
Anisotropic complexes again were converted to an isotropic state upon
heating under controlled humidity. The clearing temperatures distinctly
depend on humidity and rise with increasing length of the alkyl sulfonate.
This may allow the use of the complexes as humidity sensors. Oriented
liquid crystalline samples are formed upon fast cooling in flat capillaries