- Sulfonate group avoids excessive alkaline hydrolysis of amide groupsConventional HPAM readily undergoes rapid alkaline hydrolysis in strong alkali, generating excessive carboxylate, causing chain breakage and viscosity loss. The chemically stable sulfonate side group of SMAS is resistant to alkali hydrolysis and reduces the overall hydrolysis rate of polymer backbone.
- Branched steric structure shields main chain from OH⁻ attackMethyl branched chains from SMAS build steric hindrance around the polymer backbone, blocking hydroxide ions from approaching and breaking carbon-carbon main chains to suppress oxidative and alkaline degradation.
- Strong hydration buffering against local high alkalinityHighly hydrophilic sulfonate groups form thick hydration shells surrounding molecular chains, weakening direct contact between alkali molecules and polymer skeleton and lowering local alkali concentration near macromolecules.
- Reduced sensitivity to alkali-triggered precipitationExcess alkali plus multivalent cations easily precipitate common HPAM. SMAS improves salt/alkali compatibility, inhibits aggregation precipitation induced by alkaline environment and keeps intact molecular structure.
- Suppression of free radical oxidative degradationAlkali activates formation oxygen/impurity ions to produce free radicals which fracture polymer chains. SMAS structure improves antioxidant capacity and slows radical-initiated chain degradation under ASP alkaline conditions.
Concise academic abstract
Sodium Methallyl Sulfonate (SMAS) resists alkaline hydrolysis via stable sulfonate and steric shielding, effectively mitigating alkali degradation of polymer in ASP flooding.
