Layer-by-layer formation of oligoelectrolyte multilayers: a combined experimental and computational study

For the first time, the combination of experimental preparation and results of fully atomistic simulations of an oligoelectrolyte multilayer (OEM) made of poly(diallyl dimethyl ammonium chloride)/poly(styrene sulfonate sodium salt) (PDADMAC/PSS) is presented. The layer-by-layer growth was carried out by dipping silica substrates in oligoelectrolyte solutions and was modeled by means of atomistic molecular dynamics simulations with a protocol that mimics the experimental procedure up to the assembly of four layers. Measurements of OEM thickness, surface roughness and amount of adsorbed oligoelectrolyte chains obtained from both approaches are compared. A good agreement between simulated and experimental results was found, with some deviations due to intrinsic limitations of both methods. However, the combination of information extracted from simulations to support the analysis of experimental data can overcome such restrictions and improve the interpretation of experimental results. On the other hand, processes dominated by slower kinetics, like the destabilization of adsorbed layers upon equilibration with the surrounding environment, are out of reach for the simulation modeling approach, but they can be investigated by monitoring in situ the oligoelectrolyte adsorption during the assembly process. This demonstrates how the synergistic use of simulation and experiments improves the knowledge of OEM properties down to the molecular scale

Aggregation number distributions and mesoglobules in dilute solutions of diblock and triblock copolymers

We investigate the aggregation number and size distributions for inter-molecular clusters of amphiphilic diblock and triblock copolymers in poor solvent at very low concentrations. Diblocks and triblocks with hydrophilic ends are shown to possess narrow distributions corresponding to formation of monodispersed mesoglobules. Diblocks with hydrophobic ends are found to produce inter-cluster multimers due to bridging by the hydrophilic middle blocks, resulting in polydisperse distributions. Implications of these observations for preparation of monodispersed nanoparticles and, potentially, understanding of the quaternary structure of proteins are discussed.Comment: 4 pages, 4 PS figures. Accepted for publication in EP

Structures and synthesis of zwitterionic polymers. Review

The structures and synthesis of polyzwitterions (polybetaines) are reviewed, emphasizing the literature of the past decade. Particular attention is given to the general challenges faced, and to successful strategies to obtain polymers with a true balance of permanent cationic and anionic groups, thus resulting in an overall zero charge. Also, the progress due to applying new methodologies from general polymer synthesis, such as controlled polymerization methods or the use of click chemical reactions is presented. Furthermore, the emerging topic of responsive (smart) polyzwitterions is addressed. The considerations and critical discussions are illustrated by typical examples

Molecular concepts, self-organisation and properties of polysoaps

The article reviews water-soluble polymers characterized by surfactant side chains, and related amphiphilic polymers. Various synthetic approaches are presented, and rules for useful molecular architectures are given. Models for the self-organization of such polymers in water are presented comparing them with the micellization of low molecular weight surfactants. Highlighting key properties of aqueous polysoap solutions such as viscosity, surface tension and solubilization power, some structure-property relationships are established. Further, the formation of mesophases and of superstructures in bulk is addressed. Finally, the functionalization of polysoaps, and potential applications are discussed

Solubilization By Polysoaps

The aqueous solubilization power of several series of micellar homopolymers and copolymers (''polysoaps'') is investigated. Using five insoluble or poorly water-soluble dyes, comparisons of the capacities are made with respect to the influence of structural variables such as the polymer backbone, the polymer geometry, the comonomer content, and the charge of the hydrophilic group. Some guidelines for polysoap structures suited for efficient solubilization are established. Noteworthy is that the solubilization capacities of the polysoaps are neither linked to the ability to reduce the surface tension of water, nor to the polarity of the solubilization sites deduced from spectroscopic probes

Novel nonionic surfactants based on sulfoxides. 2. Homo- and copolymers

The synthesis of new nonionic amphiphilic polymers of the polysoap type is described, as well as their general behaviour in aqueous solution. The polymers were prepared by homopolymerisation of acrylate polymerisable surfactants (or "surfmers"), which bear the nonionic sulfoxide moiety. Alternatively, small hydrophilic acrylate and acrylamide monomers bearing the nonionic sulfoxide moiety were copolymerised with dodecylacrylate and N-dodecyl-N-methylacrylamide. Compared to many other nonionic hydrophilic fragments, a single sulfoxide group behaves as a strongly hydrophilic fragment of small volume. However, its relative hydrophilicity depends sensitively on its precise positioning in the polymers. Properly placed, three sulfoxide groups can balance up to two dodecyl chains to obtain still water-soluble polymers that exhibit typical polysoap properties. Some of the new nonionic polymers show lyotropic liquid-crystalline behaviour at ambient temperature