Civil Engineering Reference
In-Depth Information
systems the polymer concentration needed to obtain a liquid crystalline phase is nor-
mally higher than 40 wt% [17, 92]. However in literature many reports of cellulose
[93-97] and cellulose derivative [98-102] i bers electrospun from the isotropic state can
be found.
h e i rst published work involving cellulosic i bers electrospun from a liquid crystal
phase [88] described the production of acetoxypropylcellulose (APC) i bers from an
anisotropic solution that used dimethylacetamide as solvent, with a concentration of
60 wt% in polymer.
Observation of the electrospun i bers by means of scanning electron and atomic
force microscopies showed that the electrospun i bers exhibited a spontaneous twist
along the i ber axis that is not present in i bers electrospun from the isotropic phase.
Fibers with a twist are shown in Figures 8.13 and 8.14.
Figure 8.13
Scanning electron microscopy (SEM) pictures of acetoxypropilcellulose i bers electrospun
from the liquid crystal phase. h e twist can be observed along the i ber axis (a) and its pitch is smaller for
thinner i bers. In (b) two i bers with opposite handedness are showed [88]. Copyright © 2008, WILEY-
VCH Verlag GmbH & Co. KGaA, Weinheim.
Figure 8.14
3D image, obtained by atomic force microscopy (AFM), of an electrospun i ber collected on
a l at surface. h e twisting present on the i ber is clearly visible.
