Synthesis and properties of two surfactants containing polyoxypropylene block and short branched alkyl chain

Short branched alkyl polyoxypropylene sulfates, sodium isohexyl polyoxypropylene sulfate (i-HPS) and sodium isooctyl polyoxypropylene sulfate (i-OPS) were synthetized via propoxylation, sulfation, and neutralization three-step reactions, and characterized by FT-IR and H-1 NMR. Their Krafft points were measured and the results were all below freezing point. Their critical micelle concentrations (cmc) and minimum surface tension (gamma(cmc)) determined by equilibrium surface tension were 54.74 mmol L-1 and 32.12 mN m(-1) for i-HPS, 15.57 mmol L-1 and 33.33 mN m(-1) for i-OPS, respectively. The measurement of dynamic surface tension indicated that both the equilibrium values of surface tension and the time required for reaching the equilibrium decreased with the increasing concentration of surfactant solutions. The spreading ability on paraffin film researched through dynamic contact angle revealed that the droplet of i-HPS solution presented a minimum contact angle of 58.9 degrees at a concentration of 150 mmol L-1, while the equilibrium contact angle of i-OPS droplet was 52.8 under the same condition. Their salt tolerance measurement showed that 1.0 wt% i-HPS solution and 1.0 wt% i-OPS solution could endure 183.1 g L-1, 143.9 g L-1 NaCl, 206.3 g L-1, 198.4 g L-1 MgCl2, and 229.7 g L-1, 217.9 g L-1 CaCl2, respectively. (C) 2016 Elsevier B.V. All rights reserved.