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9.2 MFC Concept and its Potential for Biomedical Applications 219

As a matter of fact, none of the existing techniques is free of disadvantages.
Except for gas foaming, most of the above-listed methods produce highly porous
scaffolds, which exhibit good biocompatibility and facilitate cell seeding and
migration. However, many of them involve the use of harmful, expensive, and
partly flammable organic solvents. These solvents have to be recycled owing to
cost and environmental concerns. What is more, the solvents may be trapped in
scaffolds. They are harmful to cells and reduce their ability to form new tissues
if not completely removed. As a result, long vacuum processing is necessary
to fully eliminate these solvents. As indicated by Mikos and Temenoff [11], the
use of solvents is the major factor that precludes fabrication of scaffolds during
surgery. Therefore, creation and implementation of an organic solvent-free
paradigm to enable in situ fabrication during surgery are challenges in tissue
engineering.
The main target of this chapter is to describe a new technique that uses
polymer blends for converting bulk polymers into nano-sized materials with
controlled nano-morphology, which does not suffer from the disadvantages of
other approaches (e.g., electrospinning). The second target is to demonstrate
that the final nano-morphology – individual noninterconnected nanofibrils or
three-dimensional (3-D) nanoporous nanofibrillar network – can be reliably
governed via presence or absence of H-bonding between the partners of the
starting polymer blend. Finally, it will be shown that the technology offered for
preparation of nano-sized polymers is environmentally friendly because the
only solvent used is water, allowing recycling and reuse of the second blend
component for the same purpose.

9.2
MFC Concept and its Potential for Biomedical Applications

Taking into account some of the basic requirements for the scaffolds, for example,
the high specific surface, which can be achieved using fibrillar and/or porous
materials, it seemed challenging to apply for their manufacturing, the concept of
microfibrils-reinforced composites (MFCs), [12–21].
There are three key requirements that must be satisfied when manufacturing an
MFC, namely, (i) the involved polymers must have sufficient drawability to allow
the formation of reinforcing fibrils to occur, (ii) both polymers must be able to be
processed at a single temperature without the onset of degradation in either poly-
mer, and (iii) the melting temperature of the reinforcing polymer must exceed
∘
that of the matrix polymer by at least 40 C to allow fibril retention during matrix
consolidation. It has to be stressed that once these requirements have been sat-
isfied, MFCs can be manufactured using standard industrial polymer processing
equipment as shown in Figure 9.3.
The process can be divided into three distinct steps, each vital to the successful
creation of a microfibril-reinforced composite: