The cholesteric phase of cellulose only occurs at high concentrations of cellulose. During
evaporation of the cellulose nanorods in a solvent, the cellulose will remain in an isotropic
state until a cholesteric transition point is hit. At that point the cellulose nanorods will begin
to form droplets of cholesteric liquid crystal, where within the droplets the liquid crystal
is cholesteric, and outside the droplets, the liquid crystal is isotropic.[26] Over time these
droplets will merge into a larger region of colesteric phase, which will coexist in equilibrium
27
with the isotropic phase.[26] Furthermore, as these droplets merge, the pitch will shrink, going
from 20 microns for the rst tactoids, to 5-6 microns for the fully formed colesteric region.[26]
In this phase, aggregation of the gold nanorods was much more of an issue than is was in
nematic alignment. Within the cholesteric region, the gold nanorods will be aligned along the
liquid crystal in order to maximize translational entropy, which means they will not possess
any rotational degrees of freedom. Furthermore, the cellulose is denser within the cholesteric
regions which means there is a larger excluded volume in the cholesteric region. However in
the isotropic state the gold nanorods will possess three rotational degrees of freedom and a
smaller excluded volume. Thus from entropy considerations alone, the gold nanorods should
tend to accumulate within the isotropic regions.
The cholesteric phase of cellulose only occurs at high concentrations of cellulose. Duringevaporation of the cellulose nanorods in a solvent, the cellulose will remain in an isotropicstate until a cholesteric transition point is hit. At that point the cellulose nanorods will beginto form droplets of cholesteric liquid crystal, where within the droplets the liquid crystalis cholesteric, and outside the droplets, the liquid crystal is isotropic.[26] Over time thesedroplets will merge into a larger region of colesteric phase, which will coexist in equilibrium27with the isotropic phase.[26] Furthermore, as these droplets merge, the pitch will shrink, goingfrom 20 microns for the rst tactoids, to 5-6 microns for the fully formed colesteric region.[26]In this phase, aggregation of the gold nanorods was much more of an issue than is was innematic alignment. Within the cholesteric region, the gold nanorods will be aligned along theliquid crystal in order to maximize translational entropy, which means they will not possessany rotational degrees of freedom. Furthermore, the cellulose is denser within the cholestericregions which means there is a larger excluded volume in the cholesteric region. However inthe isotropic state the gold nanorods will possess three rotational degrees of freedom and asmaller excluded volume. Thus from entropy considerations alone, the gold nanorods shouldtend to accumulate within the isotropic regions.
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