Chemistry Reference
In-Depth Information
(Santa Barbara, CA) were processed using the Astra V macromolecular
characterization software also from Wyatt Technology Corporation. THF was
used as the mobile phase at a flow rate of 1 mL min
1
and columns were
maintained at 40 1C. The liquid-phase samples were brought into solution
with THF stabilized with butylated hydroxytoluene from Fisher Scientific
(Suwanee, GA) at a known concentration near 4.00
10
3
gmL
1
. The
Waters' autosampler was used to make 100 mL injections from a 1 mL
sample vial. Linear polystyrene standards (Polymer Laboratories), M
n
¼
580-
100 K, M
w
/M
n
¼
1 were used for the calibration of the molecular weights
of all polymers of RPEO. The Astra V software was used to calculate the
molecular weights.
3.3.2.4 Differential Scanning Calorimetry
DSC thermograms of the test samples were recorded using a TA Instruments
(New Castle, DE) Q2000 model DSC with an autosampler. Typically, about
10 mg of the RPESO sample was accurately weighed in an aluminum pan
and sealed with pin-perforated lids. The DSC oven was ramped at 10 1C per
min to 110 1C per min to eliminate thermal history and possible moisture.
A refrigerated cooling system was used to equilibrate the samples at
60 1C,
from 110 1C, at a rate of 5 1C per min. Data was recorded while the oven
temperature was increased from
60 1C to 150 1C at a rate of 5 1Cpermin.
The DSC method applied an inert atmosphere by purging the oven with
nitrogen at 50 mL min
1
. Thermal Advantage and Universal Analysis soft-
ware provided by TA Instruments were used for data analysis.
3.3.2.5 Thermogravimetric Analysis
A TA Instruments Q500 thermogravimeter with an autosampler was used to
measure the weight loss of the SA-RPESO (super acid catalyst used) samples
under a flowing nitrogen atmosphere. Generally, 20 mg of an RPESO sample
was used in the TGA. The samples were heated from 30 to 600 1C at a heating
rate of 10 1C per min and the weight loss was recorded as a function of
temperature.
3.3.3 Hydrolysis of RPESO Polymers
A solution of 2.5 g of RPESO in 50 mL of 0.4 N NaOH was refluxed for 24 h.
The solution was then filtered with a filter paper and cooled to room tem-
perature. The resulting gel was precipitated with 80 mL of 1.0 N HCl, fol-
lowed by several washings with water, and finally with two more washings
with 10% (v/v) aqueous acetic acid. The resulting polymer was dried over-
night at 80 1C in an oven. The sample was further dried under vacuum at
70 1C to a constant weight. The procedure yielded around 2.1 g (about 84%
yield) of product, and is referred to as ''HPESO polyacid''.
