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9.5 Biomedical Application Opportunities of Nano-Sized Polymers 229

the constituting fibrils of the 3-D network become finer, approaching the nano-
range as can be concluded from Figure 9.10b. This microphotograph, taken at
higher magnification (65 000×), demonstrates that the majority of nanofibrils have
a diameter around 70 nm and the nanopores are typically between 50 and 200 nm
in size. The same images indicate another peculiarity of the system – the really
branched character of the structure formed. Some of the branching “points” are
highlighted in Figure 9.10b for a better visualization.
The effect of concentration ratio of the blend components on the formation
of 3-D network was also studied using the same model system PVA/PETG [37].
For this purpose, again samples just after the extruder die were taken and after
extraction of PVA, they were studied using SEM. Blends of PVA/PETG in three
different ratios were prepared: 30/70, 50/50, and 70/30. The respective results of
SEM demonstrated that (i) the formation of a polymer blend with a co-continuous
structure takes place during the melt blending, that is, before drawing the extru-
date and (ii) the effect of the ratio of the two blend components for the forma-
tion of co-continuous phases. The blend with the highest amount of PVA (70%)
(Figure 9.10) is characterized by the best mutual penetrating structures with the
finest fibrils as compared with the blends with less PVA (50%) and particularly the
case with the lowest PVA content (30%) [37]. For the last case of blend composi-
tion, the lack of fibrillar structures is understandable – PETG is the dominating
component (70%) in which PVA is dispersed, and using a selective for the PETG
solvent, it would be possible to isolate a PVA fibrillar structure (as a 3-D network
in the present case).

9.5
Biomedical Application Opportunities of Nano-Sized Polymers

In addition to the technical and commodity applications [38], another important
opportunity for the application of the polymer nano-sized materials is their use
for biomedical purposes. As mentioned in the Section 9.1, organ transplantation
nowadays practically has no technical problems – the main problem is the lack of
donors, and this problem is solved by the tissue engineering. The latter uses scaf-
folds from polymer materials with specific properties formulated at the beginning
of the chapter.
Comparing the above-described basic requirements for scaffolds, on the one
hand, and the fibrillar and/or porous character of the nano-sized materials manu-
factured via the MFC approach on the other, one can conclude that these materials
could be of biomedical interest. Nano-sized biodegradable biocompatible poly-
mers with a 3-D network structure seem to be particularly attractive because of
their nanoporosity and extremely high specific surface (Figures 9.5b, 9.6, 9.7a,b,
9.10b, and 9.11). An additional advantage of these materials is the fact that they are
manufactured without the use of any organic solvents as water is the only solvent.