Study on response behaviors of mixed solution of polyelectrolytes and worms under shear

Abstract

The response behaviors of a mixed solution of polyelectrolytes and wormlike micelles have seldom been noticed. This paper reports rheological synergism between wormlike micelles and hydrophobically modified polyacrylic acid (HMPAA) or polyacrylic acid (PAA). The anionic, wormlike micelle system of sodium oleate (NaOA) and a hydrotrope, benzyltrimethylammonium bromide (BTAB), was exemplified in our study. Under tuned shear conditions, the following phenomena are observed successively: rheology enhancement, shear hysteresis, shear thickening, and moduli increase upon the addition of PAA or HMPAA into wormlike micelles. There is no apparent difference at low polymer concentrations between PAA- and HMPAA-based mixed systems. Remarkable contrast on rheological responses occurs at high polymer concentrations. Combined with rheological responses, the interaction mechanism is further probed by dissipative particle dynamics simulation. Entanglement between wormlike micelles and polyelectrolytes dominantly constitutes the enrichment of the network at a low polymer concentration. Hydrophobic association originating from HMPAA plays a decisive role in its superiority over a PAA system of higher concentration. Moreover, the high salinity made an adverse impact on the stretching of the PAA backbone, which aggravates the decline of synergism.