Lyotropic Lamellar Structures of a Long-Chain Imidazolium and Their Application as Nanoreactors for X-ray-Initiated Polymerization.

The lyotropic behavior of the ternary system formed by 1-tetradecyl-3-methylimidazolium chloride, 1-decanol, and water is investigated. A lamellar mesophase is formed for a wide range of compositions and is characterized by polarized optical microscopy, low-temperature scanning electron microscopy, small- and wide-angle X-ray scattering with synchrotron radiation, and differential scanning calorimetry. This phase presents onionlike structures.

In situ X-ray polymerization: from swollen lamellae to polymer-surfactant complexes.

The influence of the monomer diallyldimethylammonium chloride (D) on the lamellar liquid crystal formed by the anionic surfactant aerosol OT (AOT) and water is investigated, determining the lamellar spacings by SAXS and the quadrupolar splittings by deuterium NMR, as a function of the D or AOT concentrations. The cationic monomer D induces a destabilization of the AOT lamellar structure such that, at a critical concentration higher than 5 wt %, macroscopic phase separation takes place. When the monomer, which is dissolved in the AOT lamellae, is polymerized in situ by X-ray initiation, a new collapsed lamellar phase appears, corresponding to the complexation of the surfactant with the resulting polymer.

Copolymer-surfactant complexes obtained in a lamellar lyotropic medium.

Polymer-surfactant complexes formed between charged copolymers and oppositely charged surfactants are analyzed as a function of the charge density in the macromolecule. Copolymers of ionizable diallyldimethylammonium chloride (DADMAC) and neutral acrylamide are obtained at different comonomer ratios. When mixed with the lamellar medium formed by the anionic surfactant 1,4-bis(2-ethylhexyl)sodium sulfosuccinate (AOT) in water, they give rise to highly condensed lamellar phases in equilibrium with another lyotropic phase.

Fluorescence study on the structure of ionic liquid aggregates in aqueous solutions.

Although ionic liquids are a relatively novel class of materials, it is well documented that they form micelles through aggregation of cation aliphatic tails. However, anion self-assembly has not yet been reported. In this study, we analyzed the intrinsic fluorescence of p-toluenesulfonate groups (tosylate) as part of the ionic liquid 1-ethyl-3-methylimidazolium tosylate ([emim][TOS]) and p-toluenesulfonic acid (pTSA), in aqueous solution.

Polyelectrolyte-surfactant complexes with long range order.

Mixtures of carboxymethyl cellulose (CMC) or hydrophobically modified CMC with an oppositely charged surfactant (benzyldimethyltetradecylammonium chloride) in water were prepared. When the global polymer concentration is 0.18% by weight and the surfactant content is high enough, a precipitate with hexagonal order is formed.

Incorporation of substituted acrylamides to the lamellar mesophase of Aerosol OT.

The structure and stability of the lamellar liquid crystal formed by the surfactant sodium bis-2ethylhexyl sulfosuccinate (AOT) in water is perturbed by small amounts of the substituted acrylamides N-isopropyl, N,N-diethyl, N-acryloylmorpholine, and N,N-dimethyl methacrylamide, as revealed by small angle X-ray scattering (SAXS), deuterium NMR, and microscopy. These molecules are water soluble and stay mostly in the water layers between lamellae, but a small fraction of them (5-19%) are incorporated into the AOT bilayers, thereby producing dramatic changes. Both, the degree of anisotropy in the water molecules hydrating AOT (quadrupolar splitting in (2)H NMR) and the long period spacing between lamellae (SAXS), decrease with addition of this molecules at low concentrations, which is attributed to the lower average headgroup density at the AOT/water interface when the acrylamide is incorporated.

Fragmentation of the lamellae and fractionation of polymer coils upon mixing poly(dimethylacrylamide) with the lamellar phase of aerosol OT in water.

The lamellar mesophase formed by surfactant 1,4-bis(2-ethylhexyl) sodium sulfosuccinate (AOT) in deuterated water is mixed with poly(dimethylacrylamide) (PDMAA) polymers of low molecular weight (Mn= (2-20) x 10(3)). The mixtures separate into microphases (lamellar plus isotropic polymer solution). Their microstructures are studied by microscopy, small-angle X-ray scattering (SAXS), and deuterium NMR (2H NMR).