Polyacrylamide and its derivatives for oil recovery

Fourier Transform Infrared (FTIR) Spectroscopy
 
FTIR spectra of the powder samples were recorded on a Nexus 470 FT-IR 
(Thermo Electron Corp.). Sample was diluted by mixing dry polyacrylamide 
microspheres with KBr at a 1:100 (w/w) ratio. Spectra were collected at 2 cm
-1
resolution 
in mid-IR region (4000–400 cm
−1
).
Thermogravimetric Analysis (TGA)
 
TGA of crosslinked micro spheres was performed (Q50, TA Instrument, U.S.A).
About 10 mg dry polyacrylamide microspheres were characterized by mass loss 
measurement under a nitrogen atmosphere. The samples were heated from 25 º
C to 105 
º
C at a heating rate of 20 º
C-min
-1
, and held isothermally at 105 º
C for 30 min to 
volatilize the free water from the samples. The samples were then scanned from 105 to 
800 º
C to record mass loss at a heating rate of 10 º
C-min
-1
.
Optical Microscope Study on the Microgel Swelling and Size 
 
Swelling kinetics of microspheres was visualized using an Olympus IX-51 optical 
microscope (Olympus America, Center Valley, Pennsylvania
).
Samples were prepared 
by dispersing dry polyacrylamide particles into DI water at a concentration of 0.5 wt.-%.
Dispersions were heated at 40 º
C for two months and visualized. The fully swollen (40 
º
C) microgel dispersions were then heated to 80 º
C for one and half months till no 

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145 
obviously additional size change was observed. Within this period, an aliquot of the 
swollen microsphere samples was collected and placed onto a clean cover glass. The 
samples were imaged under the optical microscope and pictures taken. In order to 
improve particle surface contrast against the aqueous background, brilliant blue dye (Blue 
#1) was used to stain water swollen microgel surfaces. Particle sizes were analyzed and 
collected by the software Image-J. The swelling ratio (
S
) was calculated by the following 
equation:
S = V
s
/V
d
Equation 1 
where 
V
s
and 
V
d
are respectively the measured volumes in the swollen and in the dried 
state, respectively.