scholarly journals Effect of Oxygen and Initiator Solubility on Admicellar Polymerization of Styrene on Silica Surfaces

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Pohlee Cheah ◽  
Caitlin N. Bhikha ◽  
John H. O’Haver ◽  
Adam E. Smith
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Emulsion Polymerization ◽  
Water Soluble ◽  
Polymer Yield ◽  
Radical Initiator ◽  
Admicellar Polymerization ◽  
Molecular Weights ◽  
Precipitated Silica ◽  
Free Radical Initiator

Although admicellar polymerization has been termed the surface analog of emulsion polymerization, previous reports utilizing free radical-initiated admicellar polymerization relied on high levels of the free radical initiator when compared to emulsion polymerization, likely due to the presence of oxygen in the reported admicellar polymerization systems. Admicellar polymerizations of styrene on the surface of precipitated silica initiated by either a water-soluble or a water-insoluble initiator were studied to determine the effect of dissolved oxygen and free radical initiator solubility on the kinetics, yield, and molecular weight of the polymer formed. Results show that the presence of oxygen reduces the polymer yield and limits molecular weight. The solubility of the initiator also affected the polymer formed in the admicellar polymerization of styrene. While monomer conversions and polymer yield were similar, the molecular weights of polymerizations initiated by a water-soluble initiator were higher than comparable polymerizations initiated by a water-insoluble initiator.

scholarly journals A Theoretical Antioxidant Mechanism for Cytoprotective Effect of p-AcetamideSalicylate Derivatives against Free Radical Initiator AAPH in Human Erythrocytes

2021 ◽  
Author(s):  
Valéria Barros ◽  
Glaécia Pereira ◽  
Sirlene Ota ◽  
Fernanda Melo ◽  
Ana Carolina de Jesus ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Free Radical ◽  
Molecular Mechanism ◽  
Positive Control ◽  
Human Erythrocytes ◽  
Water Soluble ◽  
Cytoprotective Effect ◽  
Potent Effect ◽  
Radical Initiator ◽  
Free Radical Initiator

The molecular mechanism of cytoprotective effect on human erythrocytes of aminophenol and salicylates associated derivatives was related to their antioxidant capacity. The oxidative hemolysis induced by water-soluble free-radical initiator 2,2’-azobis-(2-amidine-propane)-dihydrochloride (AAPH) was inhibited by drug candidates named benzaminophen (BZL), salicytamide or 5-acetamide-salicylic acid (ASL), and salibenzamide or 5-benzamide-salicylic acid (BSL) when compared to their parents salicylic acid (SAC) and acetaminophen (ACP). Trolox (TLX) was the most powerful compound and used as positive control. BZL showed a potent effect followed by ACP > BSL > ASL. SAC did not show protective effect in any evaluated concentrations. These results are in accordance with the molecular mechanism by using theoretical calculation of single electron transfers (SET), hydrogen atom transfers (HAT), and sequential proton loss electron transfer (SPLET) by means of DFT/B3LYP/6-31++G(d,p) level of theory. [1,5] Hydrogen shift between carboxyl and phenol moieties and electronic properties related to pKa and other physicalchemical properties can be involved. The molecular association approach provides protective compounds more effective than SAC.

PNIPAM-based graft copolymers prepared using potassium persulfate as free-radical initiator: synthesis reproducibility

2016 ◽  
Vol 294 (6) ◽  
pp. 981-991 ◽  
Author(s):  
Nívia N. Marques ◽  
Bruna V. Lima ◽  
Valdelice R. Silveira ◽  
Bruna L. B. Lima ◽  
Ana M. S. Maia ◽  
...  
Keyword(s):  
Free Radical ◽  
Graft Copolymers ◽  
Potassium Persulfate ◽  
Radical Initiator ◽  
Free Radical Initiator

Polymerization of Diphenylbutadiyne Derivatives in Solution by Free Radical Initiator

2007 ◽  
Vol 44 (6) ◽  
pp. 605-611 ◽  
Author(s):  
Miriam F. Beristain ◽  
Eduardo Muñoz ◽  
Takeshi Ogawa
Keyword(s):  
Free Radical ◽  
Radical Initiator ◽  
Free Radical Initiator

scholarly journals Radical scavenging activity of crude polysaccharides from Camellia sinensis

2011 ◽  
Vol 63 (3) ◽  
pp. 717-721
Author(s):  
Fan Yang ◽  
Zhiwei Yang ◽  
Jianbo Xiao
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Camellia Sinensis ◽  
Superoxide Radical ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Dependent Manner ◽  
Scavenging Activity ◽  
Concentration Dependent Manner ◽  
Molecular Weights

A preparation of crude polysaccharides (TPS) was isolated from Camellia sinensis by precipitation and ultrafiltration. TPS1, TPS2, and TPS3 had molecular weights of 240, 21.4, and 2.46 kDa, respectively. The radical scavenging activities of TPS were evaluated by DPPH free radical, hydroxyl radical and superoxide radical scavenging. These results revealed that TPS exhibited strong radical scavenging activity in a concentration-dependent manner. TPS3 with lowest molecular weight showed a higher radical scavenging activity.

1-(Trimethylsilyl)-1,2,4-triazene: A Novel Free Radical Initiator

2002 ◽  
Vol 177 (5) ◽  
pp. 1109-1116 ◽  
Author(s):  
S. Munavalli ◽  
D. K. Rohrbaugh ◽  
D. I. Rossman ◽  
H. D. Durst
Keyword(s):  
Free Radical ◽  
Radical Initiator ◽  
Free Radical Initiator

IDENTIFICATION AND PURIFICATION OF A NEW PROTEIN FROM WATER-SOLUBLE EXTRACTS OF HUMAN ADRENAL GLAND

1979 ◽  
Vol 82 (3) ◽  
pp. 383-NP ◽  
Author(s):  
M. A. AL-AWQATI ◽  
Y. B. GORDON ◽  
T. CHARD
Keyword(s):  
Molecular Weight ◽  
Adrenal Gland ◽  
Gel Filtration ◽  
Water Soluble ◽  
Double Immunodiffusion ◽  
Molecular Weights ◽  
Physicochemical Methods ◽  
Two Peaks ◽  
Sepharose 4B ◽  
New Protein

An homogenate of human foetal adrenal gland was subjected to negative immunoabsorption by column chromatography using anti-whole human serum coupled to Sepharose 4B. Two peaks were eluted and used to immunize rabbits. The antisera produced were absorbed and tested for specificity by double immunodiffusion. Two antigens, which appeared to be specific to the adrenal gland, were identified having molecular weights of 25 000 and 65 000 as determined by gel filtration. The lower molecular weight antigen was isolated by physicochemical methods and found to be a protein. The amino acid composition is reported.

Reaction products of α-tocopherol with a free radical initiator, 2,2′-azobis(2,4-dimethylvaleronitrile)

Lipids ◽  
1989 ◽  
Vol 24 (3) ◽  
pp. 204-209 ◽  
Author(s):  
Roy Yamauchi ◽  
Tomoatsu Matsui ◽  
Yasuko Satake ◽  
Koji Kato ◽  
Yoshimitsu Ueno
Keyword(s):  
Free Radical ◽  
Reaction Products ◽  
Radical Initiator ◽  
Free Radical Initiator
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