Abstract
A series of surfactive amphiphilic polymer PAADs were prepared from the copolymerization of sodium acrylate, dodecyl polyoxyethylene acrylate (DPA, a surfmer), and acrylamide under the action of a mixed initiating agent consisting of ammonium persulfate-sodium bisulfite/2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride. The aggregative behaviors of PAADs were explored by 13C nuclear magnetic resonance, a viscometer, and a surface tension instrument. It was found that the apparent viscosity and surface activity of PAADs were significantly improved by the increase of average sequence length of hydrophobic micro blocks, strong intermolecular hydrophobic association, or the formation of mixed micelles between hydrophobic micro blocks and micromolecular surface-active agent. The introduction of long-chain alkyls on molecular chains prolonged the average sequence length of hydrophobic micro blocks in molecular chains and enhanced the hydrophobic association between molecular chains and the tight arrangement of molecular chains on water surfaces, thereby increasing the surface activity. Moreover, the anionic monomer sodium acrylate on molecular chains, via electrostatic repulsion, promoted the conversion from intrachain association to intermolecular association and thereby facilitated the formation of dense interfacial films, enhancing the surface activity of water solutions. Then, the anion surfmer sodium dodecylbenzenesulfonate interacted with the hydrophobic micro blocks on the molecular chains to form mixed micelles, which accelerated the interchain association and enhanced the polymer surface activity. The novel polymeric micelle with higher viscosifying ability and surface activity was expected to be a promising oil drive agent for tertiary oil recovery.
Highlights
Amphiphilic water-soluble polymer molecules contain incompatible hydrophilic chain segments and hydrophobic chain segments
The higher viscosifying ability [1] and lower molecular surface activity [2] of polymers are mainly induced by the intramolecular association and intermolecular association generated by weak intermolecular forces, such as hydrophobic interaction of hydrophobic groups in aqueous solutions [3]
The hydrophobic association polymers containing long-chain hydrophobic alkyls are prone to generating intermolecular association and significant surface activity under low concentrations [4]
Summary
Amphiphilic water-soluble polymer molecules contain incompatible hydrophilic chain segments and hydrophobic chain segments. The hydrophobic association polymers containing long-chain hydrophobic alkyls are prone to generating intermolecular association and significant surface activity under low concentrations [4]. It was indicated that the hydrophobic association ability of hydrophobic components was enhanced with the prolonging of chain length, but at the cost of polymer insolubility. This problem was not overcome until the appearance of polymerizable surface-active monomers, which provided a new route for preparation of polymers with hydrophobic micro block structures. Dodecyl polyoxyethylene acrylate (DPA) is a nonionic polymerizable surfmer monomer, and its water solution even has high dissolving ability and low surface tension under high mineralization condition. We studied how the dose of the surfmer monomer, the dose of the ionic monomer, and the dose of sodium dodecyl sulfonate (SDS) would affect the aggregation in the polymer solutions, as well as the relationship between polymer structures and solution performances
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