Polyacrylamide and its derivatives for oil recovery

particle suspension was obtained, without aggregation, in brine. 
The suspension contained particles within a 0.5 to 1 micron size range, which 
easily pass through the reservoir channel. When the micro-gel particles reached the 
desired location, decomposition of the labile cross-linker in the kernel particles lead to 
particle absorption of water and volume expansion. Furthermore, the particles were 
observed to interact with each other on a larger scale that was from 10 to 30 times larger 
than the original single particle size.[297] In high permeability, porous media, the micro-
gel could be enhanced by increasing micro-gel concentration.[298] 
Ensuing after the successful application of Bright Water, many similar swellable 
polymers or DDG[207-209, 299-301] were developed. For example, Moradi-Araghi et 
al.[302] invented stable, cross-linked water-soluble swollen polymers comprising 
expandable micro polymer particles using labile, water soluble diacrylates, such as 
PEG200 diacrylate, crosslinking agents, stable crosslinking agent monomers, e.g., 
methylene bisacrylamide, and a tertiary cross-linker such as formaldehyde or 
hexamethylenetetramine that can become activated once the labile cross-linker degrades 
under pH or temperature. The micro-gel system could be capable of being further cross-
linked to form an expanded and stable gel. The polymer particles were prepared from 
AM and AMPS through inverse-emulsion polymerization where the particles were co-
cross-linked with methylene bis-acrylamide as the stable cross-linker and either PEG-200 
or PEG-400 diacrylate as the labile cross-linker. 

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54 
There are several advantages to conducting acrylamide polymerizations by the 
inverse emulsion process. However, with these advantages there are also several 
disadvantages, including the presence of oil and the eventual phase separation of the oil 
for inherently unstable emulsions. The oil is also an undesirable field contaminant in 
most applications. Therefore, the oil is typically removed post-polymerization, replaced 
by an alternative oil phase, or simply emulsified with the micro-gel dispersion during the 
field application. 
Potential problems associated with the oil phase may be bypassed by carrying out 
the reaction in supercritical gas fluids, from which powdered products can be obtained 
directly. Supercritical fluids offer advantages in that they exhibit “liquid-like” densities 
and solvency power while having “gas-like” viscosities.[303] Currently, many polar or 
hydrophilic molecules, such as water, proteins, amides, ionic species, sugars, etc., exhibit 
very poor solubility in supercritical carbon dioxide (ScCO
2
)and only limited research 
efforts have been made towards polymerization of water-soluble vinylic monomers 
containing amides in ScCO
2
, including inverse emulsion polymerization of 
acrylamide,[304] polymerization of N-ethylacrylamide, and dispersion copolymerization 
of N,N-dimethylacrylamide.[305]
Inverse-emulsion polymerization in ScCO
2
requires that the monomer be 
relatively insoluble in ScCO
2
. Adamsky et al.[304] reported the inverse-emulsion 
polymerization of AM monomer in ScCO
2
. The key point for the emulsion 
polymerization was to choose the proper emulsifying agent. Adamsky et al. synthesized 
an emulsifier with a carbon dioxide compatible, fluorine and also amido groups. (see 

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55 
Figure 15) By virtue of the CO
2
-soluble amphiphiles, acrylamide was successfully 
polymerized using inverse-emulsion polymerization in ScCO
2
. 
F
CF CF
2
O
CF
NH
2
CF
3
CF
3
O
14