Polyacrylamide and its derivatives for oil recovery

RESULTS AND DISCUSSION
 
Inverse Suspension Polymerization without Water
 
A water-free, inverse suspension polymerization for synthesis polyacrylamide 
microgel was attempted. The detailed procedure is described in the experimental section.
Crosslinked, dry polymer spheres were produced directly, with minimal need for post 
treatment of the products, e.g., dehydration, crushing or grinding. The reaction consumed 
little surfactant, ~2 wt.-% of the system, compared to normal inverse 
emulsion/suspension polymerizations with water, which can require more than a 10 wt.-
% concentration in aqueous systems.
27,32-34
Solvents were recycled by distillation and 
reuse.
During initial polymerizations, it was observed that the polarity of the reaction 
(glass) flask inner surface affected the polymerization result. Product was observed to 
adhere and nucleate on the glass reactor wall when a clean glass inner surface was used.
The adhering products were aggregated, dry, and firm polymer. As reaction continued, 
the aggregated particles would continue to grow on the aggregation with few free 
particles observed in the liquid suspension. However, the issue was preventable by 
treating the inner surface of the reaction flask with a long aliphatic chain (C-18) silane 
coating. Wall adsorption by polymer particles was then effectively prevented and normal 
suspension polymerization resulted. 
Two crosslinking comonomers, MBAM and PEGDA, were employed in the 
reaction. Swelling expansions of the hydrogels were expected to have time-temperature 
dependency due to the combination of the dual crosslinkers with different thermal 
stability. MBAM was utilized as a thermally stable crosslinker, while the PEGDA was 

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thermally labile.
15
MBAM was previously found to be stable to at least 90~100 º
C.
35,36
Owing to ether and ester linkages in the molecule, aqueous PEGDA was prone to degrade 
quickly when temperature reached 70~80 º
C.
15
A two stage expansion was desired, 
having a fixed, swollen particle diameter in aqueous dispersion at ambient temperature 
and then a second, larger diameter upon exposure to an elevated temperature.