The effect of the uptake of a low-molecular-weight amphiphilic diblock copolymer on the morphology of didodecyldimethylammonium bromide (DDAB) adsorbed layers on mica, the interactions between two coated surfaces, and the frictional properties of the boundary film have been studied using an atomic force microscope and a dynamic surface forces apparatus nanotribometer. When DDAB-coated surfaces in aqueous solution were compressed, hemifusion or removal of the adsorbed surfactant bilayers could not be induced, and no frictional force could be measured between the surfaces, which display superior lateral cohesion and lubricant properties. Coadsorbing octadecyl end modified poly(ethylene oxide) chains at low density facilitates hemifusion, generating significant shear stress and leading to stick-slip instabilities. The mixed films regain their lateral cohesion at higher adsorbed copolymer densities, but an extra short-range attraction brings the adsorbed layers into adhesive contact without causing bilayer hemifusion. Here, noticeable frictional forces are also measured.

The formation of adsorbed surfactant layers consisting of a mesh or network of branched cylindrical aggregates on muscovite mica by several surfactant systems is described. The curvature of the adsorbed aggregates is varied by a variety of mechanisms that all generate morphologies between adsorbed cylinders and bilayers, and the resulting lateral structure is imaged by "soft contact" atomic force microscopy. We compare the direct images and Fourier transforms of the adsorbed layer structures, and relate them to those formed in bulk solution.

The structure of adsorbed layers of several polyoxyethylene alkyl ether (C(n)E(m)) nonionic surfactants on silica and graphite surfaces has been imaged using atomic force microscopy as a function of temperature up to their cloud points. For all surfactants with a cloud point within the experimentally accessible range, the adsorbed layer morphology on silica evolved from globules at low temperatures first into rods and then a mesh with increasing temperature. This mesh structure was retained even when the solutions were heated above their cloud points into the two-phase coexistence region. Only C(12)E(3) was observed to form a laterally unstructured bilayer. On graphite, all surfactants formed straight, parallel hemicylinders at all temperatures examined.

The synthesis of a series of co-oligomer amphiphiles by RAFT and their self-assembly behavior in water is described. These novel amphiphiles, comprised of styrene, butyl acrylate, and alkyl hydrophobes together with ionic acrylic acid and nonionic hydroxyethylacrylate hydrophilic moieties and with a total degree of polymerization from 5 to 17, represent a new class of small-molecule surfactants that can be formed from the immense potential library of all polymerizable monomers. Examples of micellar solutions and discrete cubic, hexagonal, lamellar, and inverted hexagonal lyotropic phases, as well as vesicle dispersions and coexisting lamellar phases, are reported and characterized by small-angle scattering. The variation of self-assembly structure with co-oligomer composition, concentration, and solution conditions is interpreted by analogy with the surfactant packing parameter used for conventional small-molecule amphiphile ABSTRACT: The synthesis of a series of co-oligomer amphiphiles by RAFT and their self-assembly behavior in water is described. These novel amphiphiles, comprised of styrene, butyl acrylate, and alkyl hydrophobes together with ionic acrylic acid and nonionic hydroxyethylacrylate hydrophilic moieties and with a total degree of polymerization from 5 to 17, represent a new class of smallmolecule surfactants that can be formed from the immense potential library of all polymerizable monomers. Examples of micellar solutions and discrete cubic, hexagonal, lamellar, and inverted hexagonal lyotropic phases, as well as vesicle dispersions and coexisting lamellar phases, are reported and characterized by small-angle scattering. The variation of self-assembly structure with co-oligomer composition, concentration, and solution conditions is interpreted by analogy with the surfactant packing parameter used for conventional small-molecule amphiphiles.