The temperature-composition phase diagram in the diluted region of the cationic surfactant cetyldimethylbenzylammonium salicylate/water system was studied with a battery of techniques. The Krafft temperature (T k = 33 ± 1°C) was measured by differential scanning calorimetry, polarizing microscopy, conductimetry, viscosimetry, and rheometry. The critical vesicle concentration (cvc, *0.002 wt%) and a vesicle-micellar transition (cvm, *0.005 wt%) was detected at a temperature of 35°C. Below T k and concentrations B2 wt%, a transparent solution is formed (I). Above 2-8.5 wt%, a lamellar (L 1 ) phase forms. At higher concentrations and up to 12 wt%, a second lamellar phase (L 2 ) is detected. From 12.4 to 15.5 wt%, an emulsion phase (E) is formed. Rheological dynamic measurements for the I phase indicate that the system exhibits a predominantly viscous behavior (G 0 \ G 00 ) for concentrations lower than the overlap or entanglement concentration (C e , *0.75 wt%). At higher concentrations, wormlike micelles form and the elastic behavior predominates (G 0 [ G 00 ). The elastic (G 0 ) modulus collapses in a concentration-time master curve in the whole reduced frequencies range xs c examined, whereas the viscous modulus (G 00 ) collapses only at reduced frequencies lower than 0.1. Reduced stress plotted as a function of the reduced shear rate yields a good superposition of the curves at the different concentrations up to the onset of the non-linear behavior.

In the following article, stable nanohydrogels (NHGs) of poly (acrylamide-coacrylic acid) (PAAm-co-PAA) were synthesized by batch polymerization (BP) and semicontinuous (SP) polymerization processes. As crosslinking agents, N,N 0 -methylenebisacrylamide (NMBAM) and ethylene glycol dimethacrylate (EGDMA) were used; docusate sodium salt (AOT) was used as a surfactant. The initiators employed in this work were 2,2 0 -Azobis(2-methylpropionamidine) dihydrochloride (V-50), potassium peroxydisulfate (KPS), peroxydisulfuric acid diammonium salt (APS), and dibenzoyl peroxide (BPO). The compositions of acrylamide/acrylic acid (AAm/AA) (90/10, 70/30, 50/50, w/w), the type of a crosslinking agent, and the type of initiator on pH response of water-dispersed NHGs were investigated. The NHGs were characterized by dynamic light scattering (DLS). Latexes with average particle size (Dpz) from 53 to 125 nm were obtained using NMBAM and EGDMA by BP polymerization processes. In contrast, NHGs synthesized by SP polymerization processes showed a Dpz ranging from 73 to 125 nm using NMBAM and EGDMA. On the other hand, the Dpz of the NHGs dispersed in water was found to be from 126 to 302 nm with NMBAM and EGDMA, respectively. Furthermore, the Dpz of the NHGs depended on the pH; higher pH values produced high Dpz values. The spherical morphology was maintained at the studied pH.