Biomedical Engineering Reference
In-Depth Information
Water in large
superpores that
can be squeezed
from cryogel
mechanically
60
Water in small
superpores
30
Polymer
bound
water
Dry
Polymer
0
1
2
3
4
Figure 14.11.
Composition of pAAm-MGs. Polymer bound water was quantifi ed by the
adsorption of water vapors by the dried cryogel sample. pAAm-MGs were dried in an oven at
60 °C to constant weight. The dried sample was incubated in a closed chamber saturated with
water vapors but with no direct contact with water. The water in small pores was quantifi ed as
the difference between total water and mechanically squeezed + adsorbed water. Reproduced
from [Plieva et al., 2004a] with permission.
TABLE 14.3. Pore Volume of p AA m - MG s Prepared at
−
12 ° C from the Feedstock with
Different Monomer Concentration
Monomer
concentration in the
feed, % w/v
Porosity, %
Water vapor adsorption
Cyclohexane uptake
Swelling
6
93
93
88.4
10
86.6
85
86.5
15
81.6
79.2
80.2
18
74.7
72.5
74
22
70.1
68
65.6
Reproduced from [Plieva et al., 2005] with permission.
The amount of bulk water in MG was determined using differential scanning
calorimetric (DSC) analysis as the amount of freezable water that is not bound by
hydrogen bonding [Kim et al., 2004; Plieva et al., 2005; Shibukawa et al., 1999].
The amount of freezable water decreased and the amount of bound water
increased with increasing monomer concentration in the feed for the MGs pre-
pared from PVA (Table 14.4). Pore volume estimated from DSC studies was in a
good agreement with the values of pore volume obtained through water vapor
adsorption studies as was shown for PVA-MGs [Plieva et al., 2006b].
Due to the presence of large (capillary-sized) and highly interconnected
pores, a majority of MGs with pore volume in the range of 85-94% can be dried
with no distortion of the porous structure. Dried MGs re-swell within seconds
when contacted with water (Figure 14.12) [Plieva et al., 2007a]. This is one of the
most important properties of these hydrophilic materials as drying simplifi es
storage of the MGs.
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