لخّصلي

1. Surface Morphological Patterns
The surface morphology of a single filament which is typical for
PLA/PHB/DPD blend nanofibers (9/1 þ 1% DPD) and the
surface pattern of the PHB/PLA/DPD blend film are shown in
Figure 1 (A and C, respectively) for the comparison. Additionally,
the AFM image of the same single fiber is presented in
Figure 1B. Both micrographs (A,C) obtained by different
techniques indicate that the melt-electrospun nanofibers with
the PHB/PLA blend ratio 1:9 have a uniform structure without
any features of cylindrical form deformation. Additionally, the
surface of filaments is quite perfect and has not visible cracks
and pores. Almost at the same SEM magnification the surface of
the molded films with the analogues PHB/PLA proportion looks
lightly structured with uneven Pt-shading density that corresponds to the alternation of petty bulges and notches.
In our previous paper[9] it was reported, that the PHB loading
to PLA matrix decreases the mean fiber diameter from
20.0 2.5 μm at the 9:1 ratio to 18.8 2.5 μm at the 7:3 ratio
and finally to 10.6 2.5 μm at the PLA/PHB ratio equals to 6:4.
The drug embedding in the polymer system decreases the mean
fiber diameter up to 10.7 2.5 μm for 7:3 þ1% DPD system and
simultaneously leads to narrower diameter distribution. As it
can show in Figure 1A,B the averaged diameters of the fibers
coincide well with the newly obtained results on the diameter
dimensions which are equal to 10 μm and 12.2 μm respectively
obtained by SEM and AFM techniques.[16]
The variance in structure-morphology characteristics of
polymer fibers obtained via classical solvent electrospinning
and corresponding films obtained via solution casting could be
explained by the discrepancy in the formation conditions and
primarily by the difference of solvent evaporation conditions. In
framework of diffusion model, the rate of solvent desorption
from an ultrathin cylindrical filament with diameter about
100 nm (107 m) and from the surface of a plane macroscopic
film with the thickness equals to about 100 μm (104 m) should
differ by as much as six order. For instance, in the work[17] it was
stated that for the nanofibers under electrospinning conditions
the time of desorption should take several millisecond, while
solvent evaporation from the films with analogous content is
gradually performed for essentially longer time, namely dozens
of hours and even more.
In event of melt electrospinning and subsequent comparison
of the spun fibers with the macroscopic molded films, the
differences in the conditions of their production are not so
obvious and related to heat dissipation more likely, that is, by
cooling specification of fibers and films. It is quite difficult to
describe the differences in temperature gradients for the
formation of fibers and films from a melt and such description