Macromolecular Reaction Engineering最新文献

Methods for the evaluation of the Damkohler number for monomer transport during emulsion homopolymerization and copolymerization are extended to the analysis of gaseous monomers. Results indicate that the monomer transport limitation of gaseous monomers in both homo and copolymerization is strongly dependent on overall pressure through Henry's law relationship governing the concentration of monomer in the aqueous phase in equilibrium with monomer bubbles. At low pressures, most monomers studied exhibit monomer transport limitations; however, even at very high pressures, some gaseous monomers still exhibit monomer transport limitations.

Front Cover: In article number 2300031, Carlos Bruno Barreto Luna and co-workers develop reactive blends of polyamide 6 and acrylic acid-grafted polyethylene (PE-g-AA). The PE-g-AA carboxylic groups react with the amine terminal groups of polyamide 6, forming the amide group and interface stabilizing the PA6/PE-g-AA blend. This promote a refinement of the dispersed PE-g-AA particles in polyamide 6, generating high-performance in impact strength and elongation at break.

The mean-square radius of gyration of network polymers can be correlated with the graph diameter, and the fraction d of segments located in the diameter chain is used to investigate the dimensions of large-sized network polymers whose cycle rank is over 10³. A simplified Monte Carlo simulation model for the miniemulsion vinyl/divinyl copolymerization is used for the generation of large-sized network polymers, assuming the classical chemical kinetics are valid. Both conventional free-radical polymerization and living polymerization are considered, and the heterogeneity of network architecture is controlled by changing the reactivity ratio of double bond in divinyl monomer with respect to that in vinyl monomer. The network maturity index (NMI) which is the cycle rank per primary chain is used to represent the degree of development of the network architecture. As the NMI increases to be well-developed, the calibrated d, defined by d_c = d/f_d where f_d is a calibration constant that shows the degree of network heterogeneity, starts to follow the master curve. This characteristic behavior applies regardless of the polymerization mechanism and the heterogeneity of the formed network architecture. Detailed characteristics of the master curve and prospects for application to gel molecules are also discussed.

A multicomponent Flory-Huggins model is implemented and utilized to describe the liquid–liquid equilibrium phenomenon in mixtures of polypropylene and xylene, in the context of the well-known xylene solubles (XS) test. The XS experiment is a common procedure in many polymer laboratories, used to determine the percentage of xylene solubles in samples of polypropylene, which provides an approximate measure of the atactic and oligomeric chains. Despite the importance of the test, the literature lacks a thermodynamic perspective regarding the description of this extraction phenomenon. In the present study, the Flory-Huggins interaction parameter is adjusted in a multicomponent framework to ensure that equilibrium chain length distributions calculated with the proposed model best match experimental distributions. It is shown that the experimental data obtained from XS analyses can be accurately fitted by the proposed model and that the estimated Flory-Huggins interaction parameter is more sensitive to the polymer average molar mass than to the degree of tacticity, when a particular catalyst is considered.

Front Cover: In article number 2200057, Arash Alizadeh, Vasileios Touloupidis, and João B. P. Soares have developed a thermodynamic simulation package for the catalytic polymerization of olefins in autoclave slurry, loop slurry, gas-phase, and autoclave solution reactors. The simulator uses the Sanchez–Lacombe theory as one of the major thermodynamic models in the polymer industry. Simulations under industrial conditions show why thermodynamic effects must be included in olefin polymerization models.

Back Cover: Polymer networks are synthesized to selectively target trans-resveratrol. By employing a statistical design of experiments, the polymerizations are conducted using ultraviolet light initiation, thus yielding materials with molecularly imprinted binding sites tailored for trans-resveratrol. These materials are successfully applied in purifying trans-resveratrol from winemaking residues, demonstrating their practical utility. This is reported by Amir Bzainia, Rolando C. S. Dias, and Mário Rui P. F. N. Costa in article number 2200076.

Herein, the poly(ɛ-caprolactone)-poly(ethylene glycol)-poly(ɛ-caprolactone) (PCL-PEG-PCL) macro xanthate reversible addition–fragmentation chain-transfer agent is obtained on the polyethylene glycol (PEG) (600, 1000, and 1500 g mol⁻¹) block, after the addition of ɛ-caprolactone via ring-opening polymerization. Then, poly (styrene-b-ɛ-caprolactone-b-PEG-b-ɛ-caprolactone-b-styrene) pentablock copolymer is synthesized reversible addition–fragmentation chain-transfer (RAFT) solution polymerization technique via mediated PCL-PEG-PCL xanthate macro-RAFT agents and 2,2′-azobisisobutyronitrile as initiator. The products are demonstrated using Fourier transform infrared spectrophotometer (FT-IR), proton nuclear magnetic resonance (¹H-NMR), carbon nuclear magnetic resonance (¹³C-NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) analyses. First-order linear kinetic graphs of the reaction mechanism are observed with an increase in molecular weights (M_W) between 16 000 and 36 000 g mol⁻¹. The narrow dispersity (Đ = 1.40–1.48) polymer formation of styrene (St) controlled by RAFT polymerization confirms the increase in molecular weight according to the polymerization time. The reaction kinetics are first order and the rate constants are found to be k₁ = 6.16 × 10⁻⁴s⁻¹, k₂ = 6.91 × 10⁻⁴ s⁻¹ and k₃ = 7.33 × 10⁻⁴ s⁻¹. Thermal and spectroscopic analyses prove that the reactions are carried out successfully.