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Cellulose nanocrystals (CNCs) are unique, lightweight materials that possess high elastic modulus and tensile strength, making them of great interest in the formation of nanocomposite materials. However, efficient design of the composite material is essential in translating the mechanical properties of the individual CNCs into the nanocomposite film. In this work, we demonstrate the formation of structured CNC/acrylic dispersions by physical blending of the anionic CNCs with charged acrylic latex particles. By blending with large cationic latex particles, the CNCs adsorbed onto the acrylic latex surface while blending with small latex particles led to the inverse structure. Films were cast from these dispersions and the physical properties were compared with the aim of understanding the influence of the initial structure of the hybrid dispersion on the structure of the final film. A significant difference in the mechanical properties was observed based on the position of the CNCs in the initial dispersion. Adsorption of latex particles onto the CNC surface led to a random distribution of nonconnected CNCs, which contributed little to improving the Young's modulus, while adsorption of CNC onto the latex led to a honeycomb CNC network and a large increase in the Young's modulus. This work underlines the importance of particle structure on the structure and mechanical properties of nanostructured films.

Polyurethane (PU)/acrylic waterborne hybrids are an attractive class of materials with wide application possibilities, but their synthesis typically requires significant quantities of solvent which has negative economic and environmental consequences. In this work, solvent-free and surfactant-free polyurethane (PU)/acrylic waterborne hybrids were obtained by synthesizing the PU prepolymer containing carboxylic groups directly in (meth)acrylic monomers that act as solvent. Then, the mixture is dispersed in water; the PU is chain-extended with diamines, and the (meth)acrylic monomers are polymerized. It was found that, against expectations, colloidal stability did not improve with the concentration of carboxylic groups that acted as stabilizing moieties. A combination of MALDI-TOF MS analysis and Monte Carlo simulations revealed that the highly heterogeneous compositions of the short chains of the PU prepolymer and their reaction with the chain-extender in the aqueous phase were responsible for lack of control of the colloidal properties. This problem was overcome by using more hydrophobic chain-extenders that decrease the fraction of PU chains in the water phase. In this way high-solid-content stable dispersions with controlled particle size were obtained. Finally, the properties of the PU/(meth)acrylic films were studied in terms of mechanical properties and water resistance.

Surfactants are vital components of almost all heterogeneous polymerizations for maintaining colloidal stability, but they also play an important role in the kinetics and mechanism of particle nucleation. Despite many decades of research, the knowledge of adsorption-desorption surfactant kinetics and their application in (mini)emulsion polymerization is largely based on qualitative arguments. In this paper we show that the use of a quartz crystal microbalance with dissipation monitoring can provide quantitative information on both the adsorption equilibrium of ionic and nonionic surfactants, and also the kinetics of adsorption/desorption, that can be applied to the understanding of nucleation processes in (mini)emulsion polymerization. We show that surfactant dynamics and nucleation phenomena in (mini)emulsion polymerization are not dominated by diffusion phenomena linked to molecular size of surfactant as previously thought but rather are driven by the large differences in the rate of surfactant adsorption and desorption at the polymer-water interface. Finally, we show the application of this knowledge to explain the differences between nucleation processes for ionic and nonionic surfactants in emulsion polymerization.

We describe a versatile and facile route for the preparation of Janus microbeads using single emulsion droplet-based microfluidics, in which water droplets that contain a mixture of branched poly(N-isopropylacrylamide)-co-(poly(ethylene glycol)diacrylate)-co-(methacrylic acid) and colloidal particles form the basis of our approach. The colloidal particles, poly(methyl methacrylate) microspheres or titanium dioxide particles, and iron oxide nanoparticles are spatially positioned within the water droplets through gravity and an externally applied magnetic force, respectively. Evaporation of water leads to gel formation of the branched copolymer matrix as a result of physical cross-linking through hydrogen bond interactions, fixing the spatial position of the colloidal particles. The thermo- and pH-responsive nature of the branched poly(N-isopropylacrylamide) (PNIPAm)-based copolymer allows for the disintegration of the polymer network of the Janus microbeads and a triggered release of the colloidal content at temperatures below the lower critical solution temperature (LCST) and at increased pH values.

We investigate the self-assembly behavior of Janus particles with different geometries at a liquid-liquid interface. The Janus particles we focus on are characterized by a phase separation along their major axis into two hemicylinders of different wettability. We present a combination of experimental and simulation data together with detailed studies elucidating the mechanisms governing the adsorption process of Janus spheres, Janus cylinders, and Janus discs. Using the pendant drop technique, we monitor the assembly kinetics following changes in the interfacial tension of nanoparticle adsorption. According to the evolution of the interfacial tension and simulation data, we will specify the characteristics of early to late stages of the Janus particle adsorption and discuss the effect of Janus particle shape and geometry. The adsorption is characterized by three adsorption stages which are based on the different assembly kinetics and different adsorption mechanisms depending on the particle shape.