In simulations and experiments, we study the drying of films containing mixtures of large and small colloidal particles in water. During drying, the mixture stratifies into a layer of the larger particles at the bottom with a layer of the smaller particles on top. We developed a model to show that a gradient in osmotic pressure, which develops dynamically during drying, is responsible for the segregation mechanism behind stratification.

In this work we present the formation of laser induced periodic surface structures (LIPSS) on spin-coated thin films of several model aromatic polymers including poly(ethylene terephthalate), poly(trimethylene terephthalate) and poly carbonate bis-phenol A upon irradiation with femtosecond pulses of 795 and 265 nm at fluences well below the ablation threshold. LIPSS are formed with period lengths similar to the laser wavelength and parallel to the direction of the laser polarization vector. Formation of LIPSS upon IR irradiation at 795 nm, a wavelength at which the polymers absorb weakly, contrasts with the absence of LIPSS in this spectral range upon irradiation with nanosecond pulses. Real and reciprocal space characterization of LIPSS obtained by Atomic Force Microscopy (AFM) and Grazing Incidence Small Angle X-ray Scattering (GISAXS), respectively, yields well correlated morphological information. Comparison of experimental and simulated GISAXS patterns suggests that LIPSS can be suitably described considering a quasi-one-dimensional paracrystalline lattice and that irradiation parameters have an influence on the order of such a lattice. Fluorescence measurements, after laser irradiation, provide indirect information about dynamics and structure of the polymer at the molecular level. Our results indicate that the LIPSS are formed by interference of the incident and surface scattered waves. As a result of this process, heating of the polymer surface above its glass transition temperature takes place enabling LIPSS formation.

The successful development of ferroelectric polymer devices depends on the effective fabrication of polar ferroelectric crystalline nanostructures. We demonstrate, by scanning X-ray microdiffraction using synchrotron light, the heterogeneous character of high aspect ratio one-dimensional nanoarrays of poly(vinylidene fluoride-co-trifluoroethylene) copolymers supported by a residual polymer film. They were prepared by melt and solution template wetting, using porous anodic aluminum oxide as a template. The spatial evolution of different polymorphs from the mixture of paraelectric and ferroelectric crystal forms (residual film) to the pure ferroelectric form (nanoarray) is evidenced for the samples prepared by solution wetting. However, for samples prepared by melt wetting the ferroelectric phase is exclusively obtained in both the residual film and nanoarray. The crystal nuclei formed in the polymer film connected to the nanoarray play a key role in determining the formation of a crystallinity distribution gradient, where the crystallinity decreases along the first 5–10 microns in the nanorods reaching a steady value afterwards. The minimum decrease in crystallinity is revealed for samples prepared by melt wetting. The results reported in this work endeavour to enhance the understanding of crystallization under confinement for ferroelectric copolymers and reveal the parameters for improving the ferroelectric character of polymer nanostructures.

The presence of low-molar-mass surfactants in latex films results in detrimental effects on their water permeability, gloss, and adhesion. For applications such as coatings, there is a need to develop formulations that do not contain surfactants and have better water barrier properties. Having previously reported the synthesis of surfactant-free latex particles in water using low amounts (<2 wt %) of chains synthesized by controlled radical polymerization (Lesage de la Haye et al. Macromolecules2017, 50, 9315–9328), here we study the water barrier properties of films made from these particles and their application in anticorrosion coatings. When films cast from aqueous dispersions of acrylate copolymer particles stabilized with poly(sodium 4-styrenesulfonate) (PSSNa) were immersed in water for 3 days, they sorbed only 4 wt % water. This uptake is only slightly higher than the value predicted for the pure copolymer, indicating that the negative effects of any particle boundaries and hydrophilic-stabilizing molecules are minimal. This sorption of liquid water is 5 times lower than what is found in films cast from particles stabilized with the same proportion of poly(methacrylic acid) (PMAA), which is more hydrophilic than PSSNa. In water vapor with 90% relative humidity, the PSSNa-based film had an equilibrium sorption of only 4 wt %. A small increase in the PMAA content has a strong and negative impact on the barrier properties. Nuclear magnetic resonance relaxometry on polymer films after immersion in water shows that water clusters have the smallest size in the films containing PSSNa. Furthermore, these films retain their optical clarity during immersion in liquid water for up to 90 min, whereas all other compositions quickly develop opacity (“water whitening”) as a result of light scattering from sorbed water. This implies a remarkably complete coalescence and a very small density of defects, which yields properties matching those of some solvent-borne films. The latex stabilized with PSSNa is implemented as the binder in a paint formulation for application as an anticorrosive barrier coating on steel substrates and evaluated in accelerated weathering and corrosion tests. Our results demonstrate the potential of self-stabilized latex particles for the development of different applications, such as waterborne protective coatings and pressure-sensitive adhesives.