Waterborne and water-reduced coatings are increasing in relevance in many sectors as an alternative to solventborne coatings. In this work, the internal structure of waterborne polymers as a function of colloid particle size is unveiled and directly related to macroscopic water absorption. To this aim, a set of acrylic waterborne films was prepared from dispersions of different colloidal particle sizes (100, 150, and 200 nm) with the same surfactant coverage. Macroscopic water absorption and water affinity were studied by Dynamic vapor sorption (DVS) and immersion tests. Small-Angle Neutron Scattering (SANS) was used to study deuterated water diffusion with time. This revealed the presence of remnant hydrophilic colloid-colloid interphases in all films, independently of the forming colloidal size and annealing conditions. Moreover, fitting of SANS data revealed that water transport in these films happens through surfactant-rich colloid-colloid interphases or through 10 nm-wide hydrophilic paths rich in surfactant aggregates (in the range of 4 nm) when these are present. The presence of the hydrophilic paths explains the higher water uptake measured in waterborne films made from 100 nm colloids, a process so far not previously reported. This study highlights how water diffusion in waterborne films may be engineered through fine control of particle size and film formation conditions.

Microalloyed low-carbon steels strengthened by vanadium carbide (VC) nanoprecipitates are receiving increasing attention, particularly in the automotive industry. A clear understanding of the nanoprecipitate chemistry is essential for optimizing the alloy composition and processing routes, thereby enhancing the mechanical properties of such advanced steels. The chemical evolution of VC precipitates, especially regarding the incorporation of iron into the nanoprecipitates, remains uncertain. Here, a model vanadium-microalloyed low-carbon steel is studied by atomic-resolution scanning transmission electron microscopy (STEM) techniques. The steel contains nanoscale VC precipitates formed either as interphase precipitates (IP) at the austenite/ferrite interface during the austenite-to-ferrite phase transformation, or as randomly distributed precipitates (RP) in the ferrite matrix during bainite tempering. The first-time observation of carbon sublattice atoms in VC is achieved using integrated differential phase-contrast STEM (iDPC-STEM). Non-equilibrium compositions are identified under both precipitation mechanisms, with no correlation between precipitate size and associated elemental contents. Most interphase VC nanoprecipitates contain higher amounts of not only iron but also manganese compared to random VC nanoprecipitates. Complementary ex-situ small-angle neutron scattering (SANS) analysis and solute-drag effect (SDE) modeling support the co-segregation of iron and manganese into the precipitates. Manganese typically appears to form a core–shell-like structure within VC. Experimental evidence is presented for the SDE-assisted formation of manganese-rich–core (fibrous) interphase VC precipitates, and a mechanism is proposed for iron–manganese co-enrichment in random VC precipitates. This study offers new insights into future strategies to tune nanoprecipitate chemistry in microalloyed steels.

The formation of nanoscale vanadium carbide (VC) precipitates is reported in steels subjected to two different thermal treatments. The thermal treatments lead to either interphase precipitation (IP) or random precipitation (RP). Small-angle neutron scattering measurements coupled with transmission electron microscopy analysis are performed to determine the VC precipitate volume fraction and size distribution. It is seen that the samples exhibiting IP show a higher number density of VC precipitates compared to those undergoing RP. Moreover, a broader size distribution of the precipitate radii is observed in the samples with RP, where lens-shaped nanoscale VC precipitates are found predominantly at grain boundaries (GBs) and sub-grain boundaries (SGBs), with smaller precipitates dispersed within the matrix. It is seen that the addition of carbon and vanadium does not increase the VC precipitate number density when the mechanism of precipitation is IP, whereas an increase in the VC precipitate number density with carbon and vanadium addition is seen in case of RP.

P3HT is a semiconducting polymer widely used in solution-processable photovoltaic research. Measuring the solubility of P3HT in organic solvents is usually an arduous and time-consuming process. Here we report the presence or absence of P3HT nanoparticle agglomeration in optically opaque solutions of P3HT, with concentrations ranging from 6.2 to 22.0 mg·mL⁻¹, in pure chloroform and in chloroform:acetone mixtures, using the neutron scattering technique, Spin-Echo Small Angle Neutron Scattering (SESANS). We demonstrate in-situ that the solubility of P3HT decreases from ∼ 22.0 mg/mL to < 6.2 mg/mL when the amount of acetone in solution increases from 0 vol% to 60 vol%. This work uses the ability of SESANS to probe P3HT nanoparticle aggregates, with dimensions ranging from ∼ 1 to several microns, in P3HT solutions with concentrations above the solubility limit.

We describe an experiment that strongly supports a two-path interferometric model in which the spin-up and spin-down components of each neutron propagate coherently along spatially separated parallel paths in a typical neutron spin-echo small-angle scattering (SESANS) experiment. Specifically, we show that the usual semi-classical, single-path treatment of Larmor precession of a polarized neutron in an external magnetic field predicts a damping as a function of the spin-echo length of the SESANS signal obtained with a periodic phase grating when the transverse width of the neutron wave packet is finite. However, no such damping is observed experimentally, implying either that the Larmor model is incorrect or that the transverse extent of the wave packet is very large. In contrast, we demonstrate theoretically that a quantum-mechanical interferometric model in which the two mode-entangled (i.e., intraparticle entangled) spin states of a single neutron are separated in space when they interact with the grating accurately predicts the measured SESANS signal, which is independent of the wave packet width.

We have designed and realized a temperature and pressure controlled cell for Neutron Reflectometry (NR) and Small Angle Neutron Scattering (SANS) that is compatible with simultaneous optical transmission and resistivity measurements. The cell can accommodate samples up to 102 mm (4 inch) in diameter, can be pressurized from vacuum up to 10 bar gas pressure and the sample temperature can be controlled up to 350°C. The four single crystal quartz windows ensure both a good neutron and optical transmission and hence can be used in combination with in-situ optical transmission measurements. We present the cell and illustrate its performance with a series of neutron reflectometry experiments performed on Ta based thin films under a hydrogen containing atmosphere.

Waterborne polyurethane (WPU) has attracted significant interest as a promising alternative to solvent-based polyurethane (SPU) due to its positive impact on safety and sustainability. However, significant limitations of WPU, such as its weaker mechanical strength, limit its ability to replace SPU. Triblock amphiphilic diols are promising materials to enhance the performance of WPU due to their well-defined hydrophobic-hydrophilic structures. Yet, our understanding of the relationship between the hydrophobic-hydrophilic arrangements of triblock amphiphilic diols and the physical properties of WPU remains limited. In this study, we show that by controlling the micellar structure of WPU in aqueous solution via the introduction of triblock amphiphilic diols, the postcuring efficiency and the resulting mechanical strength of WPU can be significantly enhanced. Small-angle neutron scattering confirmed the microstructure and spatial distribution of hydrophilic and hydrophobic segments in the engineered WPU micelles. In addition, we show that the control of the WPU micellar structure through triblock amphiphilic diols renders WPU attractive in the applications of controlled release, such as drug delivery. Here, curcumin was used as a model hydrophobic drug, and the drug release behavior from WPU-micellar-based drug delivery systems was characterized. It was found that curcumin-loaded WPU drug delivery systems were highly biocompatible and exhibited antibacterial properties in vitro. Furthermore, the sustained release profile of the drug was found to be dependent on the structure of the triblock amphiphilic diols, suggesting the possibility of controlling the drug release profile via the selection of triblock amphiphilic diols. This work shows that by shedding light on the structure-property relationship of triblock amphiphilic diol-containing WPU micelles, we may enhance the applicability of WPU systems and move closer to realizing their promising potential in real-life applications.

The spin-echo small-angle neutron scattering (SESANS) technique utilises a series of inclined magnetic fields before and after the sample to encode the scattering angle into the polarisation to obtain a much higher resolution than in conventional SANS. The analogous technique (spin echo modulated SANS (SEMSANS)) implements spin manipulations before the sample only to encode the scattering into an intensity modulation. The technique can be combined with SANS to expand the length scale range probed from 1 nm to microns. Using McStas we show that using a series of four magnetic Wollaston prisms in two orthogonal pairs with a 90° rotation can be utilised to create SEMSANS modulations in 2-D. These modulations can also be of different periods in each encoding direction. This method can be applied to anisotropic scattering samples. Also this allows for the simultaneous measurement at two orthogonal independent spin-echo lengths. This technique yields directly information about the structure of oriented structures.