Short Note. Comments on the Paper By V. Lužáková, V. Reiser and M. Košik: “Free Radical Chain Polymerization of Vinyl Monomers in Wood “in situ” with Reference to Wood Accessory Components”, Holzforschung 28 (1), 1–4 (1974)

Holzforschung ◽  
1975 ◽  
Vol 29 (3) ◽  
pp. 110-111
Author(s):  
M. Mičko ◽  
L. Paszner
Keyword(s):  
Free Radical ◽  
Short Note ◽  
Vinyl Monomers ◽  
Radical Chain ◽  
Chain Polymerization

Kinetics of the thermal reactions of ethylene. Part II. Ethylene–ethane mixtures

1968 ◽  
Vol 46 (14) ◽  
pp. 2427-2433 ◽  
Author(s):  
M. L. Boyd ◽  
M. H. Back
Keyword(s):  
Free Radical ◽  
Product Formation ◽  
Radical Chain ◽  
Thermal Reactions ◽  
Temperature Range ◽  
Initiation Step ◽  
Chain Polymerization ◽  
Main Effects ◽  
Kinetics Of ◽  
Simplified Mechanism

Mixtures of ethane and ethylene have been pyrolyzed in the temperature range 563–600 °C and at pressures from 30–60 cm. The products were similar to those obtained from the pyrolysis of ethylene by itself, described m Part I, with a marked increase in the yields of the saturated products. The initial rates of product formation and the dependence of these rates on the concentration of ethane suggest that the initiation step is the same as that proposed in the pyrolysis of ethylene alone, viz.[Formula: see text]and that the reaction[Formula: see text]is not an important source of radicals. A simplified mechanism is outlined to account for the main effects of ethane on the free radical chain polymerization.

Different Solvent Free Synthetic Routes to Organic/Inorganic Hybrid Materials

1999 ◽  
Vol 576 ◽  
Author(s):  
H. Kaddami ◽  
J. F. Gerard ◽  
J. P. Pascault
Keyword(s):  
Sol Gel ◽  
Elastic Response ◽  
Radical Chain ◽  
Rich Phase ◽  
Testing Frequency ◽  
Hydrolysis And Condensation ◽  
Synthetic Routes ◽  
Simultaneous Synthesis ◽  
Chain Polymerization

ABSTRACTThe sol-gel chemistry in low-temperature conditions can be used to produce organicinorganic materials nanocomposite from the in-situ formation of silica-rich phase in a polymer matrix. Different synthetic routes have been proposed: i) hydrolysis and condensation reactions of silane end capped oligomers, ii) polymerization of hydroxyethyl methacrylate, HEMA in presence of preformed functionalized silica nanoparticles, and iii) simultaneous hydrolysis and condensation of tetraethoxysilane and polymerization of hydroxyethymeth-acrylate.Rheological investigations made during the polymerization of these three systems display many differences. Time for gelation was chosen as the time at which the loss factor, tanδ is independent on the testing frequency, or the time at which the system displays an elastic response. Vitrification phenomenon is associated with a tanδ peak. In some cases vitrification of the inorganic-rich phase interfered with the observation of gelation and the appearance of a non soluble fraction in a good solvent like tetrahydrofurane can help for attribution.During radical chain-polymerization of HEMA a classical Trommsdorff-effect was observed. It can be at the same time than the macrogelation in the case of neat HEMA or delayed by the presence of grafted SiO2 nanoparticles. During simultaneous synthesis of inorganic and organic phases, vitrification of the inorganic-rich phase occured just after macrogelation of the system.Final morphologies are strongly dependent on the occurrence of these different structural transformations.

scholarly journals The Photoinitiator Lithium Phenyl (2,4,6-Trimethylbenzoyl) Phosphinate with Exposure to 405 nm Light Is Cytotoxic to Mammalian Cells but Not Mutagenic in Bacterial Reverse Mutation Assays

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1489
Author(s):  
Alexander K. Nguyen ◽  
Peter L. Goering ◽  
Rosalie K. Elespuru ◽  
Srilekha Sarkar Das ◽  
Roger J. Narayan
Keyword(s):  
Free Radicals ◽  
Free Radical ◽  
Mammalian Cells ◽  
Light Exposure ◽  
Collecting Duct ◽  
Radical Chain ◽  
Reverse Mutation ◽  
E Coli ◽  
A Cell ◽  
Chain Polymerization

Lithium phenyl (2,4,6-trimethylbenzoyl) phosphinate (LAP) is a free radical photo-initiator used to initiate free radical chain polymerization upon light exposure, and is combined with gelatin methacryloyl (GelMA) to produce a photopolymer used in bioprinting. The free radicals produced under bioprinting conditions are potentially cytotoxic and mutagenic. Since these photo-generated free radicals are highly-reactive but short-lived, toxicity assessments should be conducted with light exposure. In this study, photorheology determined that 10 min exposure to 9.6 mW/cm2 405 nm light from an LED light source fully crosslinked 10 wt % GelMA with >3.4 mmol/L LAP, conditions that were used for subsequent cytotoxicity and mutagenicity assessments. These conditions were cytotoxic to M-1 mouse kidney collecting duct cells, a cell type susceptible to lithium toxicity. Exposure to ≤17 mmol/L (0.5 wt %) LAP without light was not cytotoxic; however, concurrent exposure to ≥3.4 mmol/L LAP and light was cytotoxic. No condition of LAP and/or light exposure evaluated was mutagenic in bacterial reverse mutation assays using S. typhimurium strains TA98, TA100 and E. coli WP2 uvrA. These data indicate that the combination of LAP and free radicals generated from photo-excited LAP is cytotoxic, but mutagenicity was not observed in bacteria under typical bioprinting conditions.

Kinetics of the thermal reactions of ethylene. Part I

1968 ◽  
Vol 46 (14) ◽  
pp. 2415-2426 ◽  
Author(s):  
M. L. Boyd ◽  
T-M. Wu ◽  
M. H. Back
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Free Radical ◽  
Induction Period ◽  
Pressure Range ◽  
Kcal Mole ◽  
Radical Chain ◽  
Thermal Reactions ◽  
Chain Polymerization ◽  
Kinetics Of

The pyrolysis of ethylene has been studied in the temperature range 500–600 °C and the pressure range 15–60 cm. The main products were ethane, propylene, butene, butadiene, and a polymer of molecular weight corresponding to C8 or higher. Small amounts of methane, butane, unsaturated C5, unsaturated C6, and benzene were also measured. Of the main products, propylene, butene, and butadiene showed an induction period, as long as several minutes at the lowest temperature. The order with respect to ethylene of ethane, propylene, and butene was close to two and the activation energy of the rates was approximately 40 kcal/mole. The results have been interpreted in terms of a free radical chain polymerization. It is suggested that the polymer formed is unstable and decomposes to yield the products for which an induction period was observed.

Recent advances in Minisci-type reactions and applications in organic synthesis

2020 ◽  
Vol 24 ◽  
Author(s):  
Wengui Wang ◽  
Shoufeng Wang
Keyword(s):  
Free Radical ◽  
Hydrogen Atom ◽  
Organic Synthesis ◽  
Radical Reactivity ◽  
Atom Loss ◽  
Radical Generation ◽  
In Situ Generation ◽  
Thermal Cleavage ◽  
Synthetic Chemist

Abstract:: Minisci-type reactions have become widely known as reactions that involve the addition of carbon-centered radicals to basic heteroarenes followed by formal hydrogen atom loss. While the originally developed protocols for radical generation remain in active use today, in recent years by a new array of radical generation strategies allow use of a wider variety of radical precursors that often operate under milder and more benign conditions. New transformations based on free radical reactivity are now available to a synthetic chemist looking to utilize a Minisci-type reaction. Radical-generation methods based on photoredox catalysis and electrochemistry, which utilize thermal cleavage or the in situ generation of reactive radical precursors, have become popular approaches. Our review will cover the remarkably literature that has appeared on this topic in recent 5 years, from 2015-01 to 2020-01, in an attempt to provide guidance to the synthetic chemist, on both the challenges that have been overcome and applications in organic synthesis.

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