Civil Engineering Reference
In-Depth Information
•
blend powder indicated the miscibility of blends;
•
cross-sections of the blends i lms showed part l miscibility; and
•
blend in formic acid solutions could form an anisotropic phase.
h e research indicates a good compatibility in the ethylcellulose/cellulose acetate
system, whereas the thermal stability of mixtures is improved compared to that of pure
ethyl cellulose [142]. h us, this blend met the best equilibrium conditions at the mem-
brane-solution interface of membrane separation in liquid chromatography experi-
ments. In this context, knowledge on the interaction force between solute and interface
of the membrane is necessary. It is observed that the interfacial adsorption properties
and hydrophilicity of ethylcellulose are improved when blending the solution with cel-
lulose acetate, and also that the alloys are superior to ethylcellulose in the separation
ei ciency for non-dissociable polar organic solutes. h e obtained results are useful
especially for orientational membrane fabrication.
Most work has been concentrated on the formation, structure and properties of ter-
nary systems composed of one cellulose derivative and mixed solvents or other poly-
mer blended solutions. h us, the liquid crystal properties of ethylcellulose/acrylic acid,
ethylcellulose/dichloroacetic acid and ethylcellulose/glacial acetic acid solutions were
studied, observing the mesophase behavior when their concentrations exceeded 0.6,
0.3, and 0.35 g/ml, respectively, at room temperature [143]. Also,
•
ethylcellulose/acrylic acid and ethylcellulose/glacial acetic acid form let -
handed cholesteric liquid crystals; and
•
ethylcellulose/dichloroacetic acid forms right-handed cholesteric liquid
crystals.
Of particular interest are the ternary systems of ethylcellulose dissolved in a mixed
solvent (acrylic acid - water or acrylic acid - glacial acetic acid) and ethylcellulose/
acrylic acid solution blended with a l exible polymer, polyacrylamide. h e conclusions
of these studies is that, for cellulosic liquid crystals application, the morphology and
optical properties of lyotropic liquid crystals can be adjusted by solvent mixing and
blending with other polymers.
Wa n g
et al
. summarized literature data [144] and showed that the cholesteric liquid
crystalline phase of cellulose derivatives can be i xed through:
• photo-crosslinking thermotropic mesophases of cellulose derivatives
containing unsaturated side chains;
•
radiation crosslinking; and
•
crosslinking of the solvents.
Banded texture is generally observed in relaxed polymer liquid crystal solutions or
melts at er shearing or annealing of the melts of the thermotropic polymer liquid crys-
tal. For the cholesteric liquid crystalline phase of cellulose derivatives in crosslinkable
solvents, the banded texture can be i xed by crosslinking. When polymerizable solvents
were used for the preparation of cholesteric liquid crystalline composites i lms, the
