Glassy states in adsorbing surfactant-microgel soft nanocomposites.

Mixtures of polymer-colloid hybrids such as star polymers and microgels with non-adsorbing polymeric additives have received a lot of attention. In these materials, the interplay between entropic forces and softness is responsible for a wealth of phenomena. By contrast, binary mixtures where one component can adsorb onto the other one have been far less studied. Yet real formulations in applications often contain low molecular weight additives that can adsorb onto soft colloids. Here we study the microstructure and rheology of soft nanocomposites made of surfactants and microgels using linear and nonlinear rheology, SAXS experiments, and cryo-TEM techniques. The results are used to build a dynamical state diagram encompassing various liquid, glassy, jammed, metastable, and reentrant liquid states, which results from a subtle interplay between enthalpic, entropic, and kinetic effects. We rationalize the rheological properties of the nanocomposites in each domain of the state diagram, thus providing exquisite solutions for designing new rheology modifiers at will.

Versatile Encapsulation Technology Based on Tailored pH-Responsive Amphiphilic Polymers: Emulsion Gels and Capsules.

We present a multipurpose technology to encapsulate hydrophobic substances in micron-sized emulsion droplets and capsules. The encapsulating agent is a comblike stimuli-responsive copolymer comprising side-chain surfactants attached to a methacrylic acid/ethyl acrylate polyelectrolyte backbone. The composition and structure of the hydrophobic moieties of the side chains are customized to tune the particle morphology and the processing conditions. The technology exploits the synergy of properties provided by the copolymer: interfacial activity, pH responsiveness, and viscoelasticity. A one-pot process produces emulsion gels or capsule dispersions consisting of a hydrophobic liquid core surrounded by a polymer shell. The dispersions resist high ionic strengths and exhibit long-term stability. The versatility of the method is demonstrated by encapsulating various hydrophobic substances covering a broad range of viscosities and polarities-conventional and technical oils, perfumes, and alkyd paints-with a high degree of morphological and rheological control.