Modeling of RAFT polymerization processes using an efficient Monte Carlo algorithm in Julia

A kinetic Monte Carlo model of a RAFT process is presented. The algorithm has been developed and implemented in Julia for the three main RAFT theories under current discussion (Slow Fragmentation, Intermediate Radical Termination and Intermediate Radical Termination with Oligomers). Julia is a modern programming language designed to achieve high-performance in numerical and scientific computing. Thanks to a careful optimization of the code, it is possible to simulate a RAFT reaction scheme in short computing times for any of the three theories. The code is benchmarked against other programming languages (MATLAB, Python, FORTRAN and C), showing that Julia presents advantages for this particular system. The model offers an efficient method for predicting average properties and molecular weight distributions of the polymer species, including the bivariate MWD of the intermediate two-arm adduct. The proposed model can also be employed to obtain additional detailed information regarding the polymer microstructure at any reaction time.Fil: Pintos, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; ArgentinaFil: Sarmoria, Claudia. Universidad Nacional del Sur. Departamento de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brandolin, Adriana. Universidad Nacional del Sur. Departamento de Ingeniería Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Asteasuain, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Química; Argentin

Mixed adsorption and surface tension prediction of nonideal ternary surfactant systems

To deal with the mixed adsorption of nonideal ternary surfactant systems, the regular solution approximation for nonideal binary surfactant systems is extended and a pseudo-binary system treatment is also proposed. With both treatments, the compositions of the mixed monolayer and the solution concentrations required to produce given surface tensions can be predicted based only on the gamma-LogC curves of individual surfactants and the pair interaction parameters. Conversely, the surface tensions of solutions with different bulk compositions can be predicted by the surface tension equations for mixed surfactant systems. Two ternary systems: SDS/Hyamine 1622/AEO7, composed of homogeneous surfactants, and AES/DPCl/AEO9, composed of commercial surfactants, in the presence of excess NaCl, are examined for the applicability of the two treatments. The results show that, in general, the pseudo-binary system treatment gives better prediction than the extended regular solution approximation, and the applicability of the latter to typical anionic/cationic/nonionic nonideal ternary surfactant systems seems to depend on the combined interaction parameter, $${\mathop {(\beta }\nolimits_{an}^s } + {\mathop \beta \nolimits_{cn}^s })/2 - {\mathop \beta \nolimits_{ac}^s }/4$$ : the more it deviates from zero, the larger the prediction difference. If $${\mathop {(\beta }\nolimits_{an}^s } + {\mathop \beta \nolimits_{cn}^s })/2 - {\mathop \beta \nolimits_{ac}^s }/4$$ rarr0, good agreements between predicted and experimental results can be obtained and both treatments, though differently derived, are interrelated and tend to be equivalent

Batch Emulsion Polymerization of Vinyl Chloride: Effect of Operating Variables on Reactor Performance

We analyze experimentally the effect of several operating conditions on conversion and molecular weight distributions of PVC obtained in batch emulsion polymerization. The operating variables studied were reaction temperature, water/monomer weight ratio, and the concentrations of initiator, emulsifier, pH regulating agent and inhibitor. We found that conversion increases with temperature and initiator concentration. It also increases with emulsifier concentration, but there is an asymptotic limit to that increase. There is an optimal water/monomer weight ratio at which the reaction rate is highest, and an optimal pH regulating agent concentration that optimizes latex quality. Average molecular weights tend to decrease slightly with conversion.Fil: Alvarez, Andrea Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Ressia, Jorge Aníbal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Aparicio, Lucrecia Vilma. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Sarmoria, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Valles, Enrique Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brandolin, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin

Probing competitive interactions in quaternary formulations

Hypothesis The interaction of amphiphilic block copolymers of the poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) group with small molecule surfactants may be “tuned” by the presence of selected alcohols, with strong interactions leading to substantial changes in (mixed) micelle morphology, whilst weaker interactions lead to coexisting micelle types. Experiments The nature and the strength of the interactions between Pluronic P123 (EO20PO70EO20) and small molecule surfactants (anionic sodium dodecylsulfate, SDS, C12SO4Na), (cationic dodecyltrimethylammonium bromide, C12TAB) and (non-ionic polyoxyethylene(23)lauryl ether, Brij 35, C12EO23OH) is expected to depend on the partitioning of the short, medium and long chain alcohols (ethanol, hexanol and decanol respectively) and was probed using tensiometry, pulsed-gradient spin-echo nuclear magnetic resonance (PGSE-NMR) and small-angle neutron scattering (SANS). Findings The SANS data for aqueous P123 solutions with added alcohols were well described by a charged spherical core/shell model for the micelle morphology. The addition of the surfactants led to significantly smaller, oblate elliptical mixed micelles in the absence of alcohols. Addition of ethanol to these systems led to a decrease in the micelle size, whereas larger micelles were observed upon addition of the longer chain alcohols. NMR studies provided complementary estimates of the micelle composition, and the partitioning of the various components into the micelle

Monitoring Access to Shared Memory-Mapped Files

The post-mortem state of a compromised system may not contain enough evidence regarding what transpired during an attack to explain the attacker's modus operandi. Current systems that reconstruct sequences of events gather potential evidence at runtime by monitoring events and objects at the system call level. The reconstruction process starts with a detection point, such as a file with suspicious contents, and establishes a dependency chain with all the processes and files that could be related to the compromise, building a path back to the origin of the attack. However, system call support is lost after a file is memory-mapped because all read and write operations on the file in memory thereafter are through memory pointers. We present a runtime monitor to log read and write operations in memory-mapped files. The basic concept of our approach is to insert a page fault monitor in the kernel's memory management subsystem. This monitor guarantees the correct ordering of the logs that represent memory access events when two or more processes operate on a file in memory. Our monitor increases accuracy to current reconstruction systems by reducing search time, search space, and false dependencies. Keywords: event reconstruction, memory mapping, causality, memory access monitor

Model for a scission-crosslinking process with both H and Y crosslinks

We present a mathematical model that may predict average molecular weights and weight fraction of solubles for polymer chains subjected to irradiation, where both scission and crosslinking are present. Two types of crosslinks are allowed: four-armed or H crosslinks, and three-armed or Y crosslinks. This is a departure from the more traditional models for irradiation, where only H crosslinks are allowed. The model is valid both in the pregel and postgel regions, and may be applied to chains with any known distribution of molecular weights. We compare predictions from the model with experimental data on polydimethylsiloxane treated with electron beams at different doses, and show that the introduction of Y crosslinks leads to a marked improvement in the quality of the predictions as compared with a more traditional model where only H type crosslinks are allowed.Fil: Sarmoria, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Valles, Enrique Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin

Spanning-tree models for A(f) homopolymerizations with intramolecular reactions

The spanning-tree approximation model is one of the models used for polymerizations with intramolecular reaction regardless of the size of the ring formed. We present a modification of this model that uses more accurate internal estimates of the probabilities of intramolecular reaction. This requires limited Monte Carlo simulations of some molecular structures, resulting in a hybrid probability model (a combined analytic and Monte Carlo model). We then extend the spanning-tree model so that it may be used in the post-gel region. We show three possible extensions of varying degrees of complexity. The resulting models for stepwise A(f) homopolymerizations have been coded into programs that run on desktop PCs in a few seconds. The models calculate the amount of intramolecular conversion, the weight-average molecular weight, the gel point, the weight fraction of soluble material, and the weight-average molecular weight of the sol fraction. We discuss the relative merits of the modified spanning-tree model and its three post-gel extensions and show sample calculations for arbitrary homopolymerization systems.Fil: Sarmoria, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Miller, D. R.. George Mason University; Estados Unido

Mathematical Modelling of Rheological Properties of Low-density Polyethylene Produced in High-Pressure Tubular Reactors

Low-density polyethylene (LDPE) is a commodity polymer widely used in a variety of applications. Due to the complexity of its molecular structure, which includes molecular weight distribution and randomly distributed long-chain branching, its rheological behavior is varied. In the present work, a mathematical model is used to predict molecular and rheological properties of LDPE produced in a high-pressure tubular under different operating conditions. The agreement between flow curve predictions and experimental data is very good, demonstrating the potential of this model as a predictive tool for industrial producers.Fil: Dietrich, Maira. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brandolin, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Sarmoria, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Asteasuain, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina16th IFAC Symposium on Advanced Control of Chemical ProcessesVeneciaItaliaInternational Federation of Automatic Contro

Peroxide modification of polyethylene. Prediction of molecular weight distributions by probability generating functions

We present a mathematical model able to describe the complete molecular weight distributions of polyethylene during reactive modification by organic peroxides. The method is applicable to batch processes, such as modification in a press or a plug-flow extruder, and in its present form is valid up to the gel point. We apply probability generating function definitions to the mass balances of radical and polymer species in the reacting medium. Three different probability generating functions are applied, each one directly applicable either to the number, weight or chromatographic distributions. These generating functions are numerically inverted to obtain the corresponding calculated molecular weight distribution. Two different inversion methods are used, and their relative performances analyzed. Predictions are compared with qualitative experimental data obtained in a press. Model predictions on molecular weight distributions are in agreement with experimental trends. © 2002 Elsevier Science Ltd. All rights reserved.Fil: Asteasuain, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Sarmoria, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Brandolin, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin