Biomedical Engineering Reference
In-Depth Information
Figure 9.3
Schematic illustration of the hydrophobic association of hydrogels, which consists
of associated micelles and fl exible polymer chains connected by neighboring associated
micelles.
In another example, a new type of physically crosslinked hydrogel via hydropho-
bic interaction was prepared. An elastic hydrogel with self-healing property was
synthesized through micellar copolymerization of AM and a small amount of
octylphenol polyethoxyether acrylate in an aqueous solution containing sodium
dodecyl sulfate at 50 ° C. The hydrophobically modifi ed polyacrylamide was synthe-
sized by the copolymerization of AM and octylphenol polyethoxyether acrylate.
After polymerization, hydrophobic association of SDS and hydrophobic microb-
locks of hydrophobically modifi ed polyacrylamide leads to the formation of associ-
ated micelles. These micelles act as crosslinking points, so three-dimensional
polymer networks were constructed as shown in Figure 9.3 [25]. Because of the
large distance between the associated micelles, all polymer chains between the
crosslinking points in the hydrogels were suffi ciently long and fl exible.
9.3
Physical Properties of Elastic Hydrogels
Some of the most important properties of elastic hydrogels are: the gel mechanical
properties, to withstand the physiological strains
in vivo
or mechanical condition-
ing
in vitro
; gel swelling properties to maintain cell viability; and the degradation
profi les to match tissue regeneration.
9.3.1
Mechanical Property
Mechanical properties of elastic hydrogels are evaluated by the measurement of
elasticity and stress relaxation. Elasticity is estimated from the tensile strength,
