Equilibrium between Poly(N,N-dimethylacrylamide) and the Lamellar Phase of Aerosol OT/Water

Abstract

A mixed amphiphilic system composed of the anionic surfactant Aerosol OT (AOT), in water forming a lamellar phase, to which is added a neutral noninteracting polymer, poly(N,N-dimethylacrylamide), is studied experimentally by SAXS, 2 H NMR, and microscopy, in a range of surfactant and polymer compositions. Addition of the polymer produces a decrease in the lamellar spacing, the decrease by the polymer being almost twice that produced by an equal volume of AOT. Microscopy reveals heterogeneity, but no macroscopic phase separation occurs. 2 H NMR detects that on increasing the polymer concentration some water is in an isotropic environment. It is inferred that the presence of the polymer induces a microscopic phase separation into a polymer-rich isotropic phase and a surfactant-rich lamellar phase, and this is tested theoretically by calculating the osmotic pressures in these two phases. In the lamellar phase, the effect of electrostatic, undulation, van der Waals, and hydration forces on the AOT bilayer is considered; in the isotropic phase, the osmotic contribution of the polymer is considered. These two pressures correlate well, supporting theoretically the hypothesis of the two phases in equilibrium.

Nonstoichiometric polymer-surfactant complexes obtained in a lamellar lyotropic medium

“…The lyotropic system Aerosol OT (AOT)/water forms lamellar mesophases in a wide range of compositions, and the incorporation of noninteracting polymers in this system has been intensively studied in our group [41,42]. Here, the effect of the incorporation of PD in the lamellar lyotropic system Aerosol OT/water is studied.…”

Effect of water soluble molecules on the stability and flexibility of lyotropic lamellar structures. Polymer molecular weight influence

“…4 as an example). The macroscopic phase separation is hindered because of the high viscosity of these systems, which makes phase separation kinetic to be too slow [43]. Fig.…”

Hidrogeles microestructurados de acrilamida y determinación de su capacidad de absorber agua y etanol

“…con agitación continua) permitiendo que el agua difunda hacia las partículas, las cuales alcanzan el hinchamiento de equilibrio cuando se forma la red; 13 lo que incrementa la cantidad de agua que pueden absorber las partículas y por lo tanto la red polimérica.…”

“…Así mismo se determino la influencia del AOT adicionado a los hidrogeles, tanto por la adición del látex como de la mezcla seca, se puede observar en la tabla 3, que la cantidad de agua que absorbe el hidrogel de AM que se preparo con AOT, es ligeramente mayor que el hidrogel de AM pura, en trabajos previos se observo que el contacto entre soluciones acuosas de AOT con polidimetilacrilamida provoca la aparición de dos fases dentro de una solución lamellar, 13 provocando que cuando se forme la red polimérica, se obtenga un gel mas heterogéneo, con mayores huecos que en la poliaAM, incrementando su capacidad de absorber agua, por lo que ambos factores, (la adición del AOT y las partículas de poliNIPA) contribuyen a incrementar la capacidad de absorber agua de los hidrogeles microestructurados.…”