Rheological Properties of Transient Networks Formed from Copolymers of Sodium Acrylate and Methacrylates Substituted with Amphiphiles: Comparison with Sodium 2-(Acrylamido)-2-methylpropanesulfonate Copolymers

Rheological properties of aqueous solutions of the random copolymer of sodium acrylate (NaAA) and a methacrylate substituted with HO(CH2CH2O)mC12H25 (C12Em), where m = 2, 6, or 25 (DEmMA), were investigated in comparison with those of the random copolymer of sodium 2-(acrylamido)-2-methylpropanesulfonate (NaAMPS) and DEmMA of similar molecular weights focusing on the effect of the length of ethylene oxide (EO) spacer (i.e., the number of m in the DEmMA unit). The pendant C12Em moieties in these copolymers form micelles through intra- and interchain associations, and hence, polymer chains are cross-linked by the micelles, forming a network structure. Steady-shear and oscillatory rheological measurements were performed for the NaAA/DEmMA and NaAMPS/DEmMA copolymers with the DEmMA contents of 12 and 10 mol %, respectively, in 0.1 M NaCl aqueous solutions of pH 10 at varying polymer concentrations (Cp). For the NaAA/DEmMA copolymer, the network was formed more favorably when the EO spacer was shorter whereas ...