scattered beads and coalescent segments.
The simultaneous presence of beading and coalescence
processes, although limited, is due to the high polydispersity
of gelatin molecular weights. In fact, the average molecular
mass of gelatin with a low bloom number of 100 is around
25,000, but its solutions may contain significant fractions of
chains with molecular weights up to several times higher
and lower than the average. On the other hand, it is known
that the molecular weight of polymers greatly affects the
optimum concentration range for spinning processes in an
inverse proportional way [23]. As a consequence, the optimum
concentration range for a highly polydisperse solution is
difficult to estimate and supposes the coexistence of beads
given by the lowest molecular weight fractions with coalescent
segments determined by the highest ones. Moreover, as can
be observed by comparing the SEM images from Figures
4(b) and (d), the decrease in gelatin concentration from 40 %
to 30 % conducts to an important reduction of fiber
diameters from micrometer (~1-5 μm) to predominant submicrometer
domain (~0.2-1.4 μm), without changing the
overall pattern of resulting matrices (Figure 4(c)). In all
instances, the resulting fiber surfaces are very smooth and
only limited or no stickiness may be observed when