Brownian cluster dynamics with short range patchy interactions. Its application to polymers and step-growth polymerization

We present a novel simulation technique derived from Brownian cluster dynamics used so far to study the isotropic colloidal aggregation. It now implements the classical Kern-Frenkel potential to describe patchy interactions between particles. This technique gives access to static properties, dynamics and kinetics of the system, even far from the equilibrium. Particle thermal motions are modeled using billions of independent small random translations and rotations, constrained by the excluded volume and the connectivity. This algorithm, applied to a single polymer chain leads to correct static and dynamic properties, in the framework where hydrodynamic interactions are ignored. By varying patch angles, various chain flexibilities can be obtained. We have used this new algorithm to model step-growth polymerization under various solvent qualities. The polymerization reaction is modeled by an irreversible aggregation between patches while an isotropic finite square-well potential is superimposed to mimic the solvent quality. In bad solvent conditions, a competition between a phase separation (due to the isotropic interaction) and polymerization (due to patches) occurs. Surprisingly, an arrested network with a very peculiar structure appears. It is made of strands and nodes. Strands gather few stretched chains that dip into entangled globular nodes. These nodes act as reticulation points between the strands. The system is kinetically driven and we observe a trapped arrested structure. That demonstrates one of the strengths of this new simulation technique. It can give valuable insights about mechanisms that could be involved in the formation of stranded gels.Comment: 55 pages, 32 figure

On the Dynamics of the Deployment of Renewable Energy Production Capacities

This chapter falls within the context of modeling the deployment of renewable en-ergy production capacities in the scope of the energy transition. This problem is addressed from an energy point of view, i.e. the deployment of technologies is seen as an energy investment under the constraint that an initial budget of non-renewable energy is provided. Using the Energy Return on Energy Investment (ERoEI) characteristics of technologies, we propose MODERN, a discrete-time formalization of the deployment of renewable energy production capacities. Be-sides showing the influence of the ERoEI parameter, the model also underlines the potential benefits of designing control strategies for optimizing the deployment of production capacities, and the necessity to increase energy efficiency.Peer reviewe

Spontaneous nano-emulsification: Process optimization and modeling for the prediction of the nanoemulsion’s size and polydispersity

The aim of the present study was to optimize the size and polydispersity of a lipid nanoemulsion as a function of the oil (Labrafac® WL1349), surfactant (Kolliphor® HS 15) and cosurfactant (Span® 80) phase composition and temperature. The nanoemulsions were prepared using a low-energy self-emulsification method. The Z-average diameter and the polydispersity index (PDI) were modeled with mixture experiments. Nanoemulsions from 20 nm to 120 nm with PDI < 0.2 were obtained at the three different tested temperatures (30 °C, 50 °C and 90 °C). The nanoemulsion size was able to be controlled with the oil, surfactant and cosurfactant concentrations. Interestingly, the smallest PDIs were obtained at 30 °C, and the cosurfactant concentration was able to be adjusted to optimize the formulation and to obtain nanoemulsions in the 20–120 nm range with a PDI smaller than 0.14. These nanoemulsions have shown a good stability at 4 °C in storage conditions and at 37 °C in diluted conditions

Wer ist heute 'Ehrenmann' und 'Ehrenfrau'? Ethische und jugendkulturelle Aspekte des deutschen Jugendworts des Jahres

Eine Jury des deutschen Langenscheidt-Verlags wählt jedes Jahr das sogenannte 'Jugendwort des Jahres'. 2018 fiel diese Wahl auf 'Ehrenmann' bzw. 'Ehrenfrau' im Sinne von 'jemand, der etwas (Besonderes) für einen tut'. In der Folge fand jedoch weder eine öffentliche Auseinandersetzung über die Herkunft des Begriffs statt noch darüber, was Ehre für Jugendliche heute bedeutet. Der Artikel möchte daher zunächst darstellen, was Ehre ist und welche soziale Funktion sie erfüllt, und anschließend die besondere Bedeutung von Ehre für Jugendliche in Migrationssituationen reflektieren. Schließlich folgen eine pop- und jugendkulturelle Analyse der Herkunft und Verwendung des Ausdrucks 'Ehrenmann' (und 'Ehrenfrau') sowie eine abschließende kritische Reflexion der Jurywahl.Every year, a jury of the German Langenscheidt-Verlag chooses the so-called 'youth expression of the year' (Jugendwort des Jahres). In 2018, this choice fell on 'man/woman of honour' (Ehrenmann/Ehrenfrau), in a sense of ‚someone doing something (special) for somebody‘. Interestingly, no public discourse followed to examine the origin of this unusual expression or the meaning of 'honour' for today's youth. The article, therefore, aims to outline what honour is and which social functions it fulfils, and then to reflect the particular significance of honour for adolescents with a migrant background. This is followed by a pop- and youth-cultural analysis of the origin and use of the expression 'man of honour' as well as a concluding critical reflection of the jury's choice

Depletion from a hard wall induced by aggregation and gelation

Diffusion-limited cluster aggregation and gelation of hard spheres is simulated using off-lattice Monte Carlo simulations. A comparison is made of the wall-particle correlation function with the particle-particle correlation function over a range of volume fractions, both for the initial system of randomly distributed spheres and for the final gel state. For randomly distributed spheres the correlation functions are compared with theoretical results using the Ornstein-Zernike equation and the Percus-Yevick closure. At high volume fractions (φ > 40%) gelation has little influence on the correlation function, but for φ < 10% it is a universal function of the distance normalized by correlation length (ξ) of the bulk. The width of the depletion layer is about 0.5ξ. The concentration increases as a power law from the wall up to r ≈ ξ, where it reaches a weak maximum before decreasing to the bulk value

Monte Carlo simulation of particle aggregation and gelation: II. Pair correlation function and structure factor

Diffusion-limited cluster aggregation and gelation are studied using lattice and off-lattice Monte Carlo simulations. The pair correlation function g(r) and the structure factor S(q) of the particle gels were investigated as a function of the volume fraction (0.5\mbox{--}49\%) and time. At volume fractions below $5\%$, the gel structure is fractal on small length scales with $d_{\rm f} = 1.8$. g(r) shows a weak minimum at the correlation length ($\xi$), before reaching the average concentration at large length scales. The cut-off function of g(r) varies during the aggregation process, but at a given $t/t_{\rm g}$, where $t_{\rm g}$ is the gel time, it is a universal function of $r/\xi$. At high volume fractions, the structure is dominated by excluded-volume interactions, while at low volume fractions, it is determined by the connectivity

Structure and size distribution of percolating clusters. Comparison with gelling systems

3d lattice Monte-Carlo simulations were done to obtain the mass distribution (N(m)) and pair correlation function (g(r)) of percolating clusters. We give analytical expressions of the external cut-off functions of N(m) at the z-average mass and of g(r) at the radius of gyration. The simulation results were compared with experimental results on gel forming systems reported in the literature. The comparison shows that the experimental results are compatible with the simulation results. However, more experiments are needed before we can be confident that the percolation model is a good model for the sol-gel transition