Poly(methyl methacrylate-co-ethyl acrylate) latex particles with poly(ethylene glycol) grafts: structure and film formation

Latex barrier thin film formation on porous substrates

Here we present the formation of thin layers of barrier polymers onto mesoporous and macroporous substrates via dip coating of latex solutions. We investigated four commercially available latex solutions: polytetrafluoroethylene (PTFE), perfluoroalkoxy fluorothermoplastic (PFA), polyvinylidene chloride (PVDC), and polyolefin-based latex (Hypod). We examined the latex film formation on porous polymeric and ceramic substrates with a broad range of pore sizes from 10 to 200 nm. Our results show that both characteristics of the latex solution [glass transition temperature (Tg), particle size, and crystallinity] and the characteristics of the porous substrate (pore size and hydrophobicity) impact the film formation. We confirmed the defect-free, barrier nature of our latex thin films through scanning electron microscopy (SEM), atomic force microscopy (AFM), and hydraulically driven water permeation tests. Additionally, we found that latex concentration (not dipping time) is the most important parameter determining ultimate latex film thickness. We obtained defect-free films from PVDC and Hypod, which are "soft" polymers (Tg < room temperature), on mesoporous substrates under the conditions of slow evaporation rate of the solvent from these latex solutions. PTFE and PFA, which are "hard" polymers (Tg > room temperature), did not form continuous films on porous substrates.

Surfactant kinetics and their importance in nucleation events in (mini)emulsion polymerization revealed by quartz crystal microbalance with dissipation monitoring

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.

Spreading dynamics of a functionalized polymer latex

Functionalized polymer nanoparticles are used as binders for inorganic materials in everyday technologies such as paper and coatings. However, the functionalization can give rise to two opposing effects: It can promote adhesion via specific interactions to the substrate, but a high degree of functionalization can also hamper spreading on substrates. Here, we studied the spreading kinetics of individual functionalized vinyl acetate-co-ethylene polymer nanoparticles on inorganic substrates by atomic force microscopy (AFM) imaging. We found that the kinetics underwent a transition from a fast initial regime to a slower regime. The transition was independent of functionalization of the particles but depended on the wettability of the substrate. Furthermore, the transition from the fast regime to the slow regime occurred at a size-dependent contact angle, leading to a h ∼ a(3/2) scaling dependence between the height (h) and the width (a) of the spreading particles. Thereafter, spreading continued on a slower time scale. In the slow regime, the kinetics was blocked by a high degree of functionalization. We interpret the observations in terms of a nanoscale stick-slip transition occurring at interface stress around 6 kPa. We develop models that describe the scaling relations between the particle height and width on different substrates.