Polyacrylamide and its derivatives for oil recovery

Materials and methods 
Materials 
Preparation of poly (vinyl alcohol)/polyacrylamide interpenetrating network 
hydrogel was carried out with commercially available monomers, initiators, and reagents. 
The monomer used in preparing the primary network was acrylamide (AM, ≥98.0%, Alfa 
Aesar). Poly(vinyl alcohol) (PVA, molecular weight:78000 g/mol, 98.0% hydrolyzed, 
Sigma Aldrich) was used for formation of the second network; N, N′-methylene-
bisacrylamide (MBAM) (~99%, Sigma Aldrich) and glutaraldehyde (Grade II, 50 wt% in 
H
2
O, Sigma Aldrich) were employed as crosslinkers for AM and PVA respectively. 
Ammonium persulfate (APS, ACS reagent, ≥98.0%, Sigma Aldrich) was used as 
initiator. Hydrogen chloride (HCl, Technical, Fisher Chemical) and sodium hydroxide 
(NaOH, Fisher Chemical) were used to adjust pH. Sodium chloride (NaCl, Fisher 
Chemical) was used to prepare aqueous brine. Potassium bromide powder (KBr, ACS 
reagent, ≥99.0%, Fisher Chemical) was used as a window material for Fourier transform 
infrared spectroscopy. 

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Synthesis 
The PVA/PAM double network hydrogel was synthesized via chemically 
crosslinking PVA linear polymer in presence of free radical solution polymerization and 
crosslinking of acrylamide in a 100 mL glass bottle. By changing the weight ratios (0, 2, 
10, or 15 wt.-%) of PVA, a designed amount of PVA powder was fully dissolved in DI 
water under magnetic stirring, at temperature of 90±5 º
C. PVA solution was let to cool 
down to room temperature, then 30 g AM monomer and 0.17 wt.-% MBAM (based on 
AM) were added into PVA solution. After completely dissolving, the systematic pH was 
adjusted to3 using 3M HCl. The solution mixture was purged with argon for 30 min. to 
dioxide. A 0.05 wt.-% of APS (based on AM) and 0.1 wt.-% of glutaraldehyde (based on 
PVA) in water solution were added into system and stirred for 1 min to a uniform 
solution. Placing the reaction bottle at room temperature overnight, a semi-transparent 
double network PVA/PAM hydrogel was collected. Crude, semi-wet bulk gels were cut 
into designated size and dried prior to evaluation. A series of PVA/PAM interpenetrating 
hydrogels were prepared with different PVA content.