A simplified kinetic scheme of eythylene/α‐olefin copolymerization has been developed by adding reactions responsible for the unusual kinetic behavior to a general mechanism. The estimation of rate constants has been simplified by making physically meaningful initial guesses. Rate constants affecting yield, MWD and comonomer content have been estimated separately. Experiments were designed to investigate the effects of each rate constant independently. The obtained rate constants show that the sites which are responsible for formation of short chains with higher 1‐butene content are more active at the beginning of polymerization, while the sites which are responsible for formation of longer chains with lower 1‐butene units are more active at the final stages of polymerization.
Free radical polymerization kinetic in a bulk for three diallyl phthalate isomers – diallyl orthophthalate, diallyl isophthalate and diallyl terephthalate was investigated in a temperature range from 50 to 70 °C initiated with dicyclohexan peroxydicarbonate as initiator at three different initiator concentrations. Conversion points were measured using Fourier Transform Raman measurements. A new kinetic model for polymerization of three diallyl phthalate isomers was developed. It demands the inclusion of only two new kinetic parameters kDegC and kpc which were obtained as a ratio kDegC/kpc from an additional set of experiments conducted. Computed conversions from the proposed kinetic model show good agreement with the conversion and molecular weight measured data for all three investigated diallyl phthalate isomers.
A model for the block‐like copolymerization via continuous supported ATRP was developed, enabling the calculation of the sequence distributions of the different monomers as a function of chain length in continuous flow reactors. Polydispersity indices, copolymer compositions, and complete molecular weight distributions could be predicted. The model was extensively tested under a wide range of reaction conditions and the outcome was compared with experimental data. An almost perfect match between the simulated and experimental kinetic data (first order kinetic plots, conversions, and PDI) was observed. A reasonable fit for the composition data of the copolymers was obtained. The influence of the flow rate in the column reactor on the copolymer composition was studied.
In high‐throughput research, it is essential to use “right data” and “meaningful parameters” to reach reliable conclusions. The complexity and the large amount of data obtained from each set of experiments make the analysis of reaction data a nontrivial task. The important role of reaction kinetic modeling in the analysis of polymerization reaction data is discussed, and it is shown that the application of traditional methods for the determination of catalyst productivity can be misleading. Reaction kinetic modeling provides meaningful parameters for data analysis, gives complete information about the polymerization kinetic profile, and makes it possible to evaluate assumptions and hypotheses.
The kinetic behavior of a Ziegler‐Natta catalyst at 86 °C under homopolymerization conditions in a continuous slurry polymerization reactor is studied. The effects of ethylene and hydrogen concentrations on the polymerization rate and polymer properties such as and were investigated. A kinetic model based on two catalytic lumped sites was developed to predict polymerization rate and and from reactor operating conditions. Each lumped site is assumed to be activated instantaneously. Such activation either is spontaneous or requires an ethylene molecule. The model has high fidelity in predicting experimental observations using kinetic parameters estimated from the experimental data and is used for industrial process development, optimization, and new product development.
A kinetic Monte Carlo simulation model is developed to study the microstructure of acrylic functional copolymers, taking into account all complexities of acrylic kinetics like backbiting, β‐scission, and propagation to macromonomer. The model is used to study the bulk and solution copolymerization of butyl acrylate/hydroxyethyl methacrylate in batch and semibatch processes. The model is able to reproduce experimental findings, providing new information that might be difficult to obtain (if possible) by deterministic or experimental methods. With the simulation the influence of the polymerization conditions on the branching density and copolymer composition as a function of chain length are discussed.
The effect of adding various aluminum alkyls (R = Et, i‐Bu) on the polymerization of propylene is studied using a (2‐PhInd)2ZrCl2 pre‐catalyst. A mild deactivating effect is found upon addition of TIBA, whereas TEA shows a sharp deactivating effect. Increasing amounts of AlR3 results in a significant activity increase for TIBA, but an activity plateau for TEA. AlR3 imposes remarkably different effects on the molecular weight and stereochemical microstructure of polymers. As the TIBA concentration increases, $\overline {M} _{{\rm v}} $ increases at first, growing from 49 000 to 72 000, but subsequently drops to 40 000. For TEA, $\overline {M} _{{\rm v}} $ decreases sharply, plummeting from 49 000 to 17 000. Both TIBA and TEA increase the mmmm pentad content from 7.9 to 23.5% and 17.6%, respectively.
Several types of fibrous material containing poly(3‐hydroxybutyrate) (PHB), nanosized TiO2‐anatase (nanoTiO2), and chitosan oligomers are prepared by combining the electrospinning, electrospraying, and impregnation techniques. Simultaneous electrospinning/electrospraying provides uniform distribution of electrosprayed nanoTiO2 along the PHB fibers and throughout the mat. Hybrid materials of different design manifest excellent photocatalytic activity, even after repeated use. They exhibit high bactericidal activity against Escherichia coli. In addition, the fibrous scaffolds are compatible with human mesenchymal stem cells and provide a favorable environment for their development.
