Chemistry Reference
In-Depth Information
ring-opening polymerization of ESO, 30 g of ESO was added to the reactor,
which was then sealed. N
2
was purged into the reactor for 5 min. CO
2
was
pumped in until the reactor pressure, 62.1 bar, was reached. A controller (Parr
4843) was used to control the temperature. Once the reactor was brought to
the appropriate temperature (generally 25 1C), BF
3
OEt
2
was charged into the
reactor by using a Rheodyne injector. Then CO
2
was pumped in to clear the
injection loop at a pump pressure of 65.5 bar. After reaction for 2 h, 2 mL of
ethanol/H
2
O (1 : 1) was added to the reactor to deactivate the catalyst. The
white-colored polymers (RPESO) were washed sequentially with 5% aqueous
sodium bicarbonate, and H
2
O. The RPESO polymer was dried in a vacuum at
60 1C. About 28-30 g of the RPESO sample was obtained. Soxhlet extraction
with hexane as the refluxing solvent was used to extract the soluble substance
from the RPESO samples for analysis. The details of the preparation of PSBO,
RPESO and RPEuO were reported by Liu and co-workers.
15-17
3.3.2 Analysis
3.3.2.1 Fourier-transform Infrared Spectroscopy
FT-IR spectra were recorded on a Thermo Nicolet Nexus 470 FT-IR system
(Madison, WI) coupled with a Smart ARK accessory for liquid samples in a
scanning range of 650-4000 cm
1
for 32 scans at a spectral resolution of
4cm
1
. Solid samples were recorded on this FT-IR system coupled with the
Smart Orbit accessory.
3.3.2.2 Nuclear Magnetic Resonance Spectroscopy
1
H-NMR and
13
C-NMR spectra for the extracted soluble substances from
the RPESO samples were recorded using a Bruker (Rheinstetten, Germany)
ARX-500 NMR spectrometer operating at a frequency of 500.13 and
125.77 MHz, respectively, using a 5 mm inverse Z-gradient probe in
CDCl
3
(Cambridge Isotope Laboratories, Andover, MA). Solid-state
13
C-NMR
spectra for extracted insoluble substances were recorded using a Bruker
ARX-300. NMR spectrometer operation at a frequency of 300.12 and 75.46 MHz.
3.3.2.3 Gel Permeation Chromatography
GPC profiles were obtained on a Waters HPLC system including a 1515
isocratic HPLC pump, 717 plus automated injector, column heater, and
controlled with the Breeze software obtained from Waters Corporation
(Milford, MA). The columns used for separation were a pair of PLgel 3 mm
MIXED-E, 300
7.5 mm columns and a PLgel 5 mm guard, 50
7.5 mm
column (part numbers PL1110-6300, PL1110-1520, respectively) from
Polymer Laboratories (Varian, Inc., Amherst, MA). Signals generated from
a mini-DAWN TREOS triple-angle light-scattering detector and Optilab rEX
refractive index (RI) detector obtained from Wyatt Technology Corporation
