Bacterial Cellulose and Its Polymeric Nanocomposites - The Nanoscience and Technology of Renewable Biomaterials - page 248

2.0

P10
P10 BC 0.15
P10 BC 0.23
P10 BC 0.31
P10 BC 0.61

1.5

1.0

0.5

0.0

0.0 0.1 0.2 0.3

Strain

0.4 0.5 0.6

Figure9.16 Tensilemoduli of 4compositeswith10%PVAandvariousBCcontents (0.15
to0.61%) for cycle6 (28). (Journal of Biomedical Materials Research, Part B: Applied Bio-
materials, 79B (2), 2006, 245-53. Copyright 2006 JohnWiley&Sons, Inc. Reprintedwith
permissionof JohnWiley&Sons, Inc.)

rate for these nanocomposites was significantly faster than that of porcine aorta. Such
BC/PVA nanocomposites therefore matched the tensile stiffness of living tissues while
allowing for a faster recovery during a cardiac cycle.

9.5 BC Nanocomposites via Biomimetic Approaches

Both Van der Waals and H-bond play a major role in glucan chain association and cel-
lulose crystallization. Cousins and Brown (42) proposed that the glucan chains exuded
from the enzymatic complex at the bacterial membrane spontaneously form minisheets
via Van der Waals forces and then associate into minicrystals via H-bond to finally con-
verge into cellulose I microfibrils. In acetobacter , the TC consists of a single row of
subunits, thus facilitating the spontaneous formation of sheets by van der Waals forces
in an aqueous medium. On the other hand, if mini-sheet formation occurs via H-bond,
then it suffers competition of water molecules and could further be manipulated with
appropriate H-bonding molecules. In fact, it has been repeatedly shown that when a
strong H-bonding polymer such as carboxymethyl cellulose (CMC) is added to the incu-
bation medium of BC, cellulose crystallization is altered (5, 43). As CMC concentration
increases, the resulting bacterial cellulose exhibits smaller diameter microfibrils and also
has higher I β crystalline allomorph content. For CMC derivative, it was empirically