Sciences et Ingénierie de la Matière Molle

Charge transport at solid/liquid interfaces is vital to energy conversion, electrochemistry, and biological activities. These buried interfaces are the locus where continuum approaches break down, and molecular details become of utmost importance, with traditional ensemble-averaged studies giving an incomplete picture of the dynamics. Here, we build upon recently developed single-molecule microscopy optofluidic platform, to investigate the statistics of single charge transport at aqueous hexagonal Boron Nitride interfaces, demonstrating the microscopic origin of its non-Gaussian character and the control of transport by irradiation-induced surface defects. By increasing irradiation of the hBN crystals, we modulate the morphological distribution of adsorption sites, leading to a slow-down of interfacial charge transport, akin to an increasing frictional interaction. Charge hopping displacements feature exponentially-decaying arms, strongly departing from Gaussian distributions. 2D Brownian dynamics simulations evidence that these exponential tails originate from molecular jumps between trapping sites, allowing a consistent match between statistical distributions and the effective diffusion coefficient. Our study highlights the key yet overlooked role of defects in regulating interfacial charge transport, with relevance for energy applications. Charge transport at solid/liquid interfaces is crucial for the energy realm, yet traditional methods fail to capture the underlying molecular processes. Here, a single-molecule microscopy optofluidic platform reveals how surface defects modulate charge dynamics and lead to anomalous transport.

Using confocal fluorescence microscopy in both hydrophilic and hydrophobic glass capillaries, this study explores (i) the influence of wall wettability on spontaneous emulsification at the oil/water interface and (ii) the mechanisms governing the interaction of water/oil microdroplets with solid surfaces, ultimately enhancing oil recovery during low-salinity water injection. Our findings reveal that microdroplet formation predominantly occurs on solid surfaces when they are hydrophilic, whereas in hydrophobic environments, droplets emerge at the water/oil interface, specifically within the thin film between the meniscus and the solid wall. The growth dynamics of these droplets follows distinct scaling laws depending on the wettability of the surface. Upon injection of low-salinity water, the apparent contact angle increases on hydrophilic walls but remains unchanged on hydrophobic walls. In both cases, however, the advancing meniscus leaves behind a residual oil film containing trapped water microdroplets. The mobility of these droplets whether sessile or not, depends on surface properties. Over time, they merge with the surrounding water, forming water patches within the residual oil film. As these patches expand and coalesce, they create a structure reminiscent of a two-dimensional foam. Ultimately, these patches continue to grow until the solid wall is fully exposed to the free water phase.

This study experimentally observed the flow regime transitions of polyethylene oxide solutions in continuous abrupt contraction–expansion microchannels with different contraction ratios. The flow regimes and normalized vortex lengths in the contraction and expansion parts of each cavity were provided for various dilute solutions (0.5 × 10−3 wt.% to 1.5 × 10−3 wt.%) and flow rates. By comparing the flow regimes, normalized vortex lengths, and extensional rates across four different channels, the effects of channel dimensions on polymer memory and scission were analyzed. The results show that the contraction ratio is the most critical factor determining flow regime transitions. Higher contraction ratios result in greater extensional rates, leading to faster polymer stretching, more intense scission, and quicker flow regime transitions. In lower contraction ratio channels, the polymer memory effect lasts longer, and scission is more gradual, leading to slower flow transitions. Additionally, channels with longer throat lengths are more prone to elastic instabilities in the contraction part, but the nearly identical trends in normalized vortex length and extensional rate indicate that longer throat lengths have a limited effect on the degree of polymer scission.

Heterogeneous visible light photocatalysis is a compelling approach to address sustainability in synthetic photochemistry. However, the use of solid-state photocatalysts remains very unpopular in organic synthesis because of their limited accessibility and the black-box effect associated to the lack of rational between their molecular structure and their photochemical properties. Herein, we disclose the synthesis, characterization, photocatalytic properties and synthetic applications of a simple and readily available solid-state conjugated organic polymer, poly-(para-phenylene ethynylene) 1, which exhibits a strong oxidative power upon irradiation with visible light (E(1*/1⋅-)=+1.67 V vs SCE). Comparisons with structural analogues highlighted the superior photocatalytic activity of this linear semiconductor, on account of its fully conjugated architecture. The associated excited-state reactivity enabled the transformation of various amines into imines in batch and continuous flow reactors together with straightforward photocatalyst recycling. Mechanistic investigations revealed concomitant photoredox and energy transfer pathways, that led to the formation of the desired products. Ultimately, the inline generation of imines was exploited in telescoped three-component Ugi reactions (3CR) in batch and flow toward biologically relevant α-acylaminoamides.

We have explored receding contact line dynamics on superhydrophobic surfaces, composed of micropillars arrays. We present here dynamic receding contact angle measurements of water on such surfaces, covering contact line speeds spanning over five decades. We have studied the effect of pillars fraction on dynamical receding contact angles. We compared these measurements to those on smooth surfaces with the same chemical nature and also with similar systems reported in the literature. We show that superhydrophobic surfaces exhibit a significantly lower dependence of contact angle on contact line speed compared to smooth surfaces. Additionally, we observed that a higher surface fraction of pillars leads to a greater dependence of the contact angle on contact line speed, approaching the dependence of the angle on smooth surface. Interestingly, we show that the exact texuration of the surface does not play a fundamental role in the angle-velocity relationships as long as microtextures present the same type of periodic pattern (pillar arrays or microgrid). These results are interpreted in terms of viscous friction reduction on superhydrophobic surfaces, shedding light on the underlying mechanisms governing their unique dynamic behavior. In addition we show that contact angles follow same laws for two different geometries (milimetric sessile drop and a centimetric capillary bridge).

Polymer association at liquid-liquid interfaces is a promising way to spontaneously obtain soft self-healing membranes. In the case of reversible bonding between two polymers, the macromolecules are mobile everywhere within the membrane and they can be absorbed into it at both boundaries due to binding to macromolecules of the other type. In this work, we develop the theoretical model of membrane growth based on these assumptions. The asymptotic dependence of membrane thickness on time as h ~ t^(1/2), as typically observed in experiments in a stationary regime, reveals an interdiffusion-controlled process, where the polymer fluxes sustain the polymer absorption at the membrane boundaries. The membrane growth rate is mainly determined by the difference in equilibrium compositions at the boundaries, the association constant, the polymer lengths and mobilities. This model is further used to describe the growth of hydrogel membranes formed via H-bonding of polymers at the interface between a solution of poly(propylene oxide) (PPO) in isopropyl myristate and an aqueous solution of poly(methacrylic acid) (PMAA). The film thickness is measured by reflectometric methods. The dependence of thickness on time can be approximated by the power law t^(beta), where beta= 1/2 for the PMAA solution at pH=3 and decreases with increasing pH and, hence, ionization degree. The growth rate slows down about 25 times for 500-nm-thick films at pH = 5.1 compared to the case of pH = 3. The ionization degree of PMAA solutions was studied by potentiometric methods. Even a small change in ionization was found to influence the growth rate of the film. A slowdown of the film growth for the ionized polymer can be explained by a drop in the composition gradient in the membrane, as is predicted by the proposed model.

Vitrimers are a promising class of polymer networks that feature thermally activated dynamic covalent bonds. Although promising for many applications in material science, vitrimers tend to be difficult to process because of high viscosity. Processability is commonly enhanced at the expense of mechanical performance at service temperature, and thus this trade-off remains an important challenge in the development of these materials. Herein, we report a new approach based on thermoreversible organic nanofillers (TRONs), which we define as low molar mass molecules that act as reinforcing fillers at the service temperature and plasticizers at the processing temperature. This concept is exemplified in the context of an elastomeric dioxaborolane-based polybutadiene vitrimer as a model matrix, and two different dibenzylidene sorbitol derivatives are evaluated as TRONs. We find that vitrimers loaded with TRONs exhibit improved creep resistance and tensile properties at service temperatures while also exhibiting lower viscosity at processing temperatures.

Under specific conditions, some proteins can self-assemble into fibrillar structures called amyloids. Initially, these proteins were associated with neurodegenerative diseases in eucaryotes. Nevertheless, they have now been identified in the three domains of life. In bacteria, they are involved in diverse biological processes and are usually useful for the cell. For this reason, they are classified as "functional amyloids". In this work, we focus our analysis on a bacterial functional amyloid called Hfq. Hfq is a pleiotropic regulator that mediates several aspects of genetic expression, mainly via the use of small noncoding RNAs. Our previous work showed that Hfq amyloid-fibrils interact with membranes. This interaction influences Hfq amyloid structure formation and stability, but the specifics of the lipid on the dynamics of this process is unknown. Here, we show, using spectroscopic methods, how lipids specifically drive and modulate Hfq amyloid assembly or, conversely, its disassembly. The reported effects are discussed in light of the consequences for bacterial cell life.

O artigo centra-se no processo de obra da Casa em Alenquer, iniciada em 1995 – e encomendada por Emílio Vilar (1964- ). A investigação revisita a sua importância para o atelier Aires Mateus (1988) e as circunstâncias sobre a origem do ‘processo’. A obra teve relevância no percurso profissional de Francisco Aires Mateus (1964- ) e Manuel Aires Mateus (1963- ), pela presença disciplinar e mediática – inclusive ter sido publicada em 2001, antes de estar finalizada. Nesse sentido, questionam-se as investigações que a Casa em Alenquer desenvolveu e proporcionou: circunscrevendo em conceitos. O artigo recorre exclusivamente à análise de fontes primárias, não só desde as fotografias sobre a obra/processo, desenhos originais, entre outros, pertencentes do atelier e espólio físico-digital, como também dos diversos materiais de arquivo submetidos à Câmara Municipal de Alenquer para licenciamento. Assim, propõe-se uma análise sobre a materialização da obra. A partir de materiais nunca publicados, ambiciona-se revelar o ‘processo e construir uma ‘narrativa’ sobre a Casa em Alenquer.

Sustainable monomers were designed from itaconic acid and thiolactone. These monomers enabled the preparation of multi-functional polymers according to different pathways.