Mechanistic details of ethylene polymerization reaction using methallyl nickel(ii) catalysts

2018 ◽  
Vol 20 (35) ◽  
pp. 22915-22925 ◽  
Author(s):  
Daniela E. Ortega ◽  
Diego Cortés-Arriagada ◽  
Alejandro Toro-Labbé
Keyword(s):  
Ethylene Polymerization ◽  
Polymerization Reaction ◽  
Mechanistic Study ◽  
Polyethylene Production ◽  
High Degree

We present a mechanistic study of the ligand functionalization of bulky boron co-activators on neutral methallyl Ni(ii) catalysts for polyethylene production. This provides a blueprint for the development and design of catalysts with a high degree of tunability in a more efficient way.

(Pyrazol-1-yl)carbonyl palladium complexes as catalysts for ethylene polymerization reaction

2013 ◽  
Vol 724 ◽  
pp. 95-101 ◽  
Author(s):  
Hosana D. Mkoyi ◽  
Stephen O. Ojwach ◽  
Ilia A. Guzei ◽  
James Darkwa
Keyword(s):  
Ethylene Polymerization ◽  
Palladium Complexes ◽  
Polymerization Reaction

scholarly journals Effects of Various Mixed Metal Chlorides- AlCl3 in TiCl4/MgCl2/THF Catalytic System on Ethylene Polymerization

2015 ◽  
Vol 14 (2) ◽  
pp. 12
Author(s):  
Nittaya Sudsong ◽  
Wanna Phiwkliang ◽  
Bunjerd Jongsomjit ◽  
Piyasan Praserthdam
Keyword(s):  
Catalytic System ◽  
Ethylene Polymerization ◽  
Catalyst System ◽  
Polymerization Reaction ◽  
Molar Ratio ◽  
Metal Chlorides ◽  
Mixed Metal ◽  
Icp Analysis ◽  
Co Addition

In this research, the modification of TiCl4/MgCl2/THF catalyst system with various metal chlorides was investigated on ethylene polymerization. Experimentally, metal chlorides (CaCl2, FeCl2 and ZnCl2) were simultaneously introduced different with TiCl4/MgCl2/THF catalyst. ICP analysis was used to determine the total amount of each metal in the catalyst. For polymerization reaction, TEA was used as cocatalyst and hexane was used as a medium solvent. The Al/Ti molar ratio was 140. The activity result of Ca-Al, Zn-Al and Fe-Al was 979, 1009 and 1476 kgPE/molTi.h, respectively. The coaddition of AlCl3 and FeCl2 in TiCl4/MgCl2/THF catalyst system exhibited the highest activity. It suggested that the co-addition of AlCl3 and FeCl2 has higher electronegativity (EN) and the radius of Fe2+ is closer to Mg2+ resulting in an increased efficiency of the THF removal. This result led to improve the catalyst performance.

scholarly journals Polywave And Monowave Light-Curing Units Effects On Polymerization Efficiency Of Different Photoinitiators

2021 ◽  
Vol 24 (4) ◽  
Author(s):  
Peterson Oliveira Boeira ◽  
Mateus De Azevedo Kinalski ◽  
Mateus Bertolini Fernandes dos Santos ◽  
Rafael Ratto de Moraes ◽  
Giana Silveira Lima
Keyword(s):  
Phosphine Oxide ◽  
Second Generation ◽  
Degree Of Conversion ◽  
Polymerization Reaction ◽  
Third Generation ◽  
Test Results ◽  
Vis Spectroscopy ◽  
Light Curing ◽  
Post Hoc ◽  
High Degree

Objective: of this study was to characterize and correlate the absorption spectra of three photoinitiators [camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO)], using second or third-generation light curing units (LCU), and to evaluate the degree of conversion and the physical properties of an experimental resin adhesive.  Material and methods: Second-generation (Radii-cal® and Emitter D®) and third-generation (Valo® Cordless and Bluephase N®) LCU were assessed regarding spectrum and irradiance rate of emitted light. Also, the photoinitiators (CQ, TPO and BAPO) were characterized by a light absorption spectrum assessed by UV-Vis spectroscopy, degree of conversion and yellowing effect. Statistical analyzes considered two-way ANOVA and post-hoc Tukey test.  Results: BAPO presented higher reactivity compared to TPO. Regarding degree of conversion of the photoinitiators activated by different light-curing units, the Emitter D® device promoted a high degree of conversion. BAPO presented the highest yellowing effect values. Conclusions: The emission and absorption characteristics of the photoinitiators were different. The polymerization reaction activated by the second-generation light-curing unit was reduced when using an experimental resin with photoinitiator TPO, and the third-generation light-curing unit showed a higher polymerization potential regardless of the photoinitiator. Keywords Light-curing of dental adhesives;  Photoinitiators dental; Curing lights dental.

scholarly journals Modeling of Ethylene Polymerization with Ziegler-Natta Catalyst in a Bubbling Fluidized Bed Reactor

2021 ◽  
Author(s):  
Neda Felorzabihi
Keyword(s):  
Molecular Weight ◽  
Kinetic Model ◽  
Fluidized Bed ◽  
Ethylene Polymerization ◽  
Fluidized Bed Reactor ◽  
Polymerization Reaction ◽  
Solid Catalyst ◽  
Gas Temperature ◽  
Natta Catalyst ◽  
Ziegler Natta Catalyst

In the present study, a new dynamic fluidized bed reactor (FBR) model is developed to account for the effect of bubble growth in the bed height on the dynamic behaviour of the reactor and the molecular properties of the polymer product. The model takes into account the existence of solid catalyst in both phases and consequently, the occurrence of polymerization reaction in both bubble and emulsion phases. A dynamic two-phase model is employed for predicting the key hydrodynamic parameters of the bed. A comprehensive kinetic model for ethylene polymerization in the presence of multiple-site Ziegler-Natta catalyst is considered to describe the number and molecular weight averages and molecular weight distribution of polymer in the FBR. The hydrodynamic model and the kinetic model have been coupled and solved simultaneously to simulate the performance of the fluidized bed reactor. The study incorporates the effects of the most important reactor parameters such as superficial gas velocity, mean particle size, inlet gas temperature, bubble size, recycle stream and chain transfer agent on the steady-state behaviour of the FBR. The proposed dynamic model is capable of predicting both the performance of the reactor and the polymer physiochemical properties.

Mechanistic Study of HCV Polymerase Inhibitors at Individual Steps of the Polymerization Reaction

Biochemistry ◽  
2006 ◽  
Vol 45 (38) ◽  
pp. 11312-11323 ◽  
Author(s):  
Yaya Liu ◽  
Wen W. Jiang ◽  
John Pratt ◽  
Todd Rockway ◽  
Kevin Harris ◽  
...  
Keyword(s):  
Polymerization Reaction ◽  
Mechanistic Study ◽  
Polymerase Inhibitors

scholarly journals DEGREE OF POLYMERIZATION OF DUAL CURE RESIN CEMENT MEASURED BY FTIR

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Aleksandra Maletin ◽  
Dubravka Marković ◽  
Isidora Nešković ◽  
Branislava Petronijević ◽  
Tanja Veljović ◽  
...  
Keyword(s):  
Clinical Success ◽  
Triethylene Glycol ◽  
Mean Value ◽  
Degree Of Polymerization ◽  
Resin Cement ◽  
Polymerization Reaction ◽  
Dental Resin ◽  
Triethylene Glycol Dimethacrylate ◽  
High Degree

Introduction: The degree of polymerization of dental resin cement materi- als is very important for the longevity and quality of the clinical success of the restorative procedure. Insufficiently effective polymerization reaction of dental resin cement materials may result in adverse effects on the mechanical and adhesive performance of the material. It is believed that the proportion of triethylene glycol dimethacrylate (TEGDMA) mono- mers in the chemical structure of the material significantly influences the polymerization reaction. With the increase in TEGDMA, the degree of conversion of monomers into the polymer increases. Aim: The aim of this study has been to determine the degree of polymerization of dual cure dental resin cement. Material and methods: For the analysis of the degree of polymerization, Fourier transform infrared (FTIR) spectroscopy was used. 10 samples of dual cure resin based cement Variolink II were prepared in accordance with the manufacturer's instructions. Analysis was performed 24 hours after polymerization procedure. Results: Degree of polymerization of Variolink II resin based cement ranged from 69.2% to 98.7% with a mean value of 85.81%. Conclusion: Variolink II dual cure resin cement contains a significant percentage of TEGDMA which can be the cause of high degree of polymerization. The minimum accep- table percentage of the degree of polymerization of dental resin cement has not yet been established.

scholarly journals Survival and Transcriptomic Response of Clinically relevant pathogens on Surfaces in Relation to Probiotic and Traditional Cleaning Strategies

2022 ◽  
Author(s):  
Jingling Hu ◽  
Weitao Shuai ◽  
Jack T. Sumner ◽  
Anahid A Moghadam ◽  
Erica M Hartmann
Keyword(s):  
Gene Expression ◽  
Klebsiella Pneumoniae ◽  
Extended Period ◽  
Mechanistic Study ◽  
Transcriptomic Response ◽  
Healthcare Facilities ◽  
Ecological Principles ◽  
Microbe Interactions ◽  
Healthcare Associated ◽  
High Degree

Prolonged survival of clinically relevant pathogens on inanimate surfaces represents a major concern in healthcare facilities. Contaminated surfaces can serve as reservoirs of potential pathogens and greatly hinder the prevention of healthcare-associated infections. Probiotic cleaning using environmental microorganisms to promote inter-species competition has been proposed as an alternative to traditional chemical-based cleaning using antimicrobials. Probiotic cleaning seeks to take advantage of ecological principles such as competitive exclusion and utilize benign microorganisms to inhibit viable pathogens on indoor surfaces. However, limited mechanistic study has yielded direct evidence that enables the scientific community to understand the stress response, or microbe-microbe interactions between healthcare-associated pathogens and probiotic bacteria. Therefore, to bridge this knowledge gap, we combined transcriptomics and traditional microbiology techniques to investigate the differential impact of chemical-based and probiotic surface cleaners on the survival of Acinetobacter baumannii and Klebsiella pneumoniae, two clinically important pathogens. Although probiotic Bacillus included in a commercialized All-Purpose Probiotic Cleaner persisted on surfaces for an extended period of time, surfaces contaminated with A. baumannii cleaned using chemical-based detergent with and without probiotic Bacillus showed no statistical difference in the viable colony forming units (CFUs) of A. baumannii. Similarly, for Klebsiella pneumoniae, there were negligible statistical differences in CFUs between probiotic and detergent cleaning scenarios. The transcriptome of A. baumannii with and without probiotic addition shared a high degree of similarity in overall gene expression, while the transcriptome of K. pneumoniae with and without probiotic addition differed in overall gene expression. Together, these results highlight the need to fully understand the underlying biological and ecological mechanisms for different pathogens and practical implications of probiotic indoor cleaning.

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