Chemistry Reference
In-Depth Information
Fig. 6.5
DSC thermograms of siloxane-containing polyesters and their corresponding monomers.
The thermograms presented were taken from the second heating scan that was done at a rate of
10 °C/min
of ln
A
(Fig.
6.6
). An examination of this graph indicates two striking features. First
there is an inflection point that occurs at 110 °C when the higher molecular weight
diol is used. Because of this, the activation energy was determined for temperatures
below this value. From the Arrhenius equation the activation energy for the silicone
diol case was found to be 44.21 kJ/mol and the Arrhenius factor was
A
= 1.607 × 10
6
.
When the disiloxane diol was used the activation energy was 44.06 kJ/mol and the
Arrhenius factor was
A
= 2.637 × 10
6
.
6.7
Residual Activity of Novozyme-435
The residual activity of N435 was determined by recovering the enzyme containing
beads and subsequently performing an assay designed to standardize for residual
activity. The assay monitors the production of octyl palmitate from 1-octanol and
palmitic acid. Control assays consisting of N435 that had never been used as well
as an enzyme-free control reaction were included. The results of each assay were
monitored using
1
H NMR. The change in the intensity of the resonances for the
O
-methylene protons in 1-octanol and octyl palmitate was compared. In the ab-
sence of any enzyme esterification was not detected. On the contrary, virgin enzyme
