Biomedical Engineering Reference
In-Depth Information
of the polyester macromer to enable HIPE formation. Polymeriza-
tion of the continuous phase of HIPEs resulted in low-density foams
with pore diameters ranging from 5 to 100
μ
m. The effect of the
diluent type on foam morphology was investigated with scanning
electron microscopy (SEM). In particular, the effect of the diluent
type (reactive: styrene or MMA; unreactive: toluene) and the ratio
of polyester to diluents was examined. Although styrene and MMA
yieldedstableHIPEsupto60wt%polyestercontent,theadditionof
toluene resulted in soft foams that collapsed upon drying. Regard-
less of the diluent type, only low levels of vinyl-terminated polester
yielded microcellular foams. PolyHIPEs with polyester concentra-
tions higher than 40 wt% displayed characteristics of phase separa-
tion.Ingeneral,20wt%polyesterpolyHIPEshadporesizessuitable
fortissueengineeringscaffolds(Fig.33.6).Cytocompatibilitystudies
on the polester-based foams using whole chicken embryo explants,
ratskinexplants,orindividualhumanskincellsindicatedpromising
cell adhesion, spreading, and proliferation up to six days.
Lumelsky
et al
. utilized two approaches for incorporating PCL
into polyHIPEs.
50
Similar to Busby
et al
., the first approach copoly-
merizedvinyl-terminatedPCLwithstyrene.
23
Thisapproachyielded
a typical polyHIPE structure with voids on the order of tens of
microns. The second approach generated semi-interpenetrating
polymer networks (semi-IPN) of a PCL diol and styrene. The rel-
atively hydrophilic PCL diol destabilized the HIPE, which resulted
in voids on the order of hundreds of microns. In contrast to the
vinyl-terminated PCL, which was covalently immobilized in the
Figure 33.6.
SEM of polyester-based polyHIPEs using styrene (S) and
methyl methacrylate (MMA) as diluents. (a) 20:80 PLA:styrene, (b) 20:80
PCL:styrene, (c) 20:80 PLA:MMA, and (d) 20:80 PCL:MMA. Scale bars
10
microns.ReprintedwithpermissionfromRef.23;copyright2001American
Chemical Society; and Ref. 46; copyright 2002 Society of Chemical Industry.
=
Search WWH ::
Custom Search