Biomedical Engineering Reference
In-Depth Information
Fig. 2
Identification of H-bond grafting mechanism.
A
ATR-FTIR spectrum highlight-
ing stretch bands of hydrogen-bonded carbonyl groups, - CO - (b), at 1700 cm
-1
,and
free carbonyl groups, - CO - (a), at 1730 cm
-1
, respectively.
B
ATR-FTIR data curves in-
dicating ratios of - CO - (b) vs - CO - (a) of each sample: SMA-MSPEO, un-modified
PEU surfaces, SPEO-modified PEU surfaces, and MSPEO-modified PEU surfaces [77].
Reproduced from [173]
of - CO - (a) and - CO - (b) was respectively measured from the parallel
samples of pure MSPEO powders, pure PEU elastomers, PEU-SPEO (5%,
w/w) elastomeric blends, and PEU-MSPEO (5%, w/w) elastomeric blends.
The quantification is demonstrated with a “- CO - (b)/- CO - (a)” profile
that is also exhibited in Fig. 2. The profile indicates that (1) in pure MSPEO
material, there are few H-bonded structures formed; (2) in pure PEU elas-
tomer, most of the PEU hard blocks are H-bonded; (3) the addition of SPEO
makes little change; however, (4) the addition of MSPEO observably enhances
the total quantity of H-bonded structures. Consequently, the conclusion is
that, compared to pure PEU, the extra H-bonded structures are generated
by the H-bond constructions between PEU hard blocks and MSPEO “C”-
blocks, namely, the SMA-MSPEO is physically grafted onto the backbone of
PEU matrix materials via H-bond conjugation. The IR spectroscopic evidence
is proven to be applicable both in the material bulk and on material sur-
faces [76, 77].
Blending Stability Evidence
The overall blending stability of SMA in the material bulk and the sur-
face “grafting” stability on material surfaces were examined by leaching
tests and evaluated respectively with proton nuclear magnetic resonance
spectroscopy [
1
H-NMR] and quantitative ATR-FT-IR. Firstly, SMA-MSPEO
and SPEO with equivalent amounts of PEG components were respectively
blended into PEU matrix materials. The initial quantity of PEG was meas-
ured and recorded by integrating the PEG-specific
1
H-NMR peak areas at
δ
= 3.52 ppm (- O - C
H
2
- C
H
2
- O -). The integral values were normalized
