Evaluating the Effect of Termination by Chain - Chain Coupling in Living Free-Radical Polymerizations

2003 ◽  
Vol 56 (8) ◽  
pp. 775 ◽  
Author(s):  
Jeffrey Pyun ◽  
Ian Rees ◽  
Jean M. J. Fréchet ◽  
Craig J. Hawker
Keyword(s):  
Free Radical ◽  
Star Polymers ◽  
Star Polymer ◽  
Direct Result ◽  
Vinyl Monomers ◽  
Linear Polymers ◽  
Radical Coupling ◽  
Novel Approach ◽  
Vis Spectroscopy ◽  
Radical Polymerizations

A novel approach based on the reaction of multifunctional star polymers with chromophore-labelled linear polymers is presented for evaluating the extent of termination by chain–chain coupling during living free-radical polymerizations. A mixed initiating system consisting of an unlabelled, multifunctional initiator and an excess of a monofunctional alkoxyamine initiator containing a chromophore, such as pyrene, is used to initiate the living polymerization of vinyl monomers leading to a mixture of star and linear polymers. The occurrence of chain–chain coupling is readily identified and quantified by isolating the star polymer that is obtained and elucidating the level of incorporation of pyrene units by UV/vis spectroscopy. This allows the level of chain–chain coupling to be determined since the inclusion of pyrene into the star structure is a direct result of termination by radical coupling.

Universal xanthate-mediated controlled free radical polymerizations of the “less activated” vinyl monomers

2010 ◽  
Vol 48 (22) ◽  
pp. 5206-5214 ◽  
Author(s):  
Yuefang Yan ◽  
Wei Zhang ◽  
Yansheng Qiu ◽  
Zhengbiao Zhang ◽  
Jian Zhu ◽  
...  
Keyword(s):  
Free Radical ◽  
Vinyl Monomers ◽  
Radical Polymerizations

Modeling of Free Radical Polymerization of Azobenzene-based Linear Polymers

2012 ◽  
Vol 1403 ◽  
Author(s):  
Danish Iqbal ◽  
C. Melchert ◽  
M. Behl ◽  
A. Lendlein ◽  
S. Beuermann
Keyword(s):  
Free Radical ◽  
Radical Polymerization ◽  
Butyl Acrylate ◽  
Software Package ◽  
Kinetic Data ◽  
Liquid Crystalline ◽  
Linear Polymers ◽  
Reasonable Approximation ◽  
Radical Polymerizations ◽  
Remarkable Agreement

ABSTRACTModeling of free radical polymerizations of the liquid-crystalline monomer 6-[4-(4-heptyloxyphenylazo)phenoxy]hexylacrylate using the PREDICI software package is reported. The model accounts for all elemental reactions that were identified to be important for radical polymerizations of acrylate-type monomers. On the basis of butyl acrylate kinetic data a remarkable agreement between number average molar masses from modelling (Mn,sim) and from experiments (Mn,exp) is observed: Mn,sim = 17800 g·mol−1 and Mn,exp = 17400 g·mol−1. Similarly, dispersity values of 1.8 and 1.6 were determined via modelling and experiments, respectively. It is shown that the assumption of butyl acrylate kinetics provides a reasonable approximation even for acrylate-based monomers having mesogenic substituents.

scholarly journals Potential of Stimuli-Responsive Star Polymer for Cancer Targeting

2021 ◽  
Vol 2 (3) ◽  
Author(s):  
Patihul Husni ◽  
Muhammad Alvien Ghifari ◽  
Norisca Aliza Putriana
Keyword(s):  
Targeted Delivery ◽  
Star Polymers ◽  
Star Polymer ◽  
Natural Phenomenon ◽  
Therapeutic Drug ◽  
Cancer Targeting ◽  
Linear Polymers ◽  
Stimuli Responsive ◽  
Redox Enzyme ◽  
External Stimuli

Application of stimuli-responsive star polymers in cancer targeting and drug delivery has been extensively researched because of their several advantages in comparison with their linear counterparts. Functionalization and recombination of various arm architectures of the star polymer are very possible to be conducted to suit various needs. The star polymers could not only load more therapeutic drug due to more arms than linear polymers but also be functionalized with targeted moieties for more targeted delivery. Furthermore, the chains in star polymers could be regulated to produce stimuli-responsive star polymer for cancer targeting. The review article aimed to describe the benefits of star polymers and the types of stimuli-responsive delivery system for cancer targeting. Over the last decade, stimuli-responsive star polymers for cancer targeting using either internal stimuli (e.g., pH, redox, enzyme, hypoxia) or external stimuli (e.g., thermal, ultrasound, light, magnetic) has garnered immense interest for researchers. Possibility to mimic a complex natural phenomenon  could be achieved by incorporating various stimuli-responsive functionalities in the star polymer.

Star Polymers of Sodium Styrenesulfonate Prepared by One-Pot TEMPO-Controlled SFRP

2012 ◽  
Vol 65 (8) ◽  
pp. 1117 ◽  
Author(s):  
Jianfu Ding ◽  
Steven Holdcroft
Keyword(s):  
Molecular Weight ◽  
Free Radical ◽  
Radical Polymerization ◽  
Star Polymers ◽  
One Pot ◽  
Stable Free Radical ◽  
Radical Coupling ◽  
Repeat Units ◽  
Divinyl Benzene ◽  
Sodium Styrenesulfonate

Star polymers of sodium styrenesulfonate with controlled arm length were prepared in a one-pot polymerization. Sodium styrenesulfonate was first polymerized with controlled molecular weight and narrow polydispersity by stable free radical polymerization. Poly(sodium styrenesulfonate) was terminated with divinyl benzene and star polymers prepared via stable free radical coupling of vinylic terminal groups. Star polymers based on arms of 20 and 32 repeat units possessed ~33 and ~41 arms per star respectively. Formation of star polymers with much longer arms was limited by poor coupling kinetics.

Enzyme-initiated free radical polymerizations of vinyl monomers using horseradish peroxidase

2019 ◽  
pp. 249-262
Author(s):  
Kyle J. Rodriguez ◽  
Michela M. Pellizzoni ◽  
Robert J. Chadwick ◽  
Chao Guo ◽  
Nico Bruns
Keyword(s):  
Free Radical ◽  
Horseradish Peroxidase ◽  
Vinyl Monomers ◽  
Radical Polymerizations

Free radical polymerizations of some vinyl monomers in carbon dioxide fluid

2008 ◽  
Vol 110 (1) ◽  
pp. 468-474 ◽  
Author(s):  
Zi Wang ◽  
Ya Jun Yang ◽  
Qing Zhi Dong ◽  
Chun Pu Hu
Keyword(s):  
Carbon Dioxide ◽  
Free Radical ◽  
Vinyl Monomers ◽  
Radical Polymerizations

Investigation of Antioxidant Activity of Pomegranate Juices by Means of Electron Paramagnetic Resonance and UV-Vis Spectroscopy

2015 ◽  
Vol 98 (4) ◽  
pp. 866-870 ◽  
Author(s):  
Violetta Kozik ◽  
Krystyna Jarzembek ◽  
Agnieszka Jędrzejowska ◽  
Andrzej Bąk ◽  
Justyna Polak ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radical ◽  
Epr Spectroscopy ◽  
Antioxidant Properties ◽  
Free Radical Scavenger ◽  
Pomegranate Juice ◽  
Radical Scavenger ◽  
Paramagnetic Resonance ◽  
Vis Spectroscopy ◽  
Electron Paramagnetic

Abstract Pomegranate fruit (Punica granatum L.) is a source of numerous phenolic compounds, and it contains flavonoids such as anthocyanins, anthocyanidins, cyanidins, catechins and other complexes of flavonoids, ellagitannins, and hydrolyzed tannins. Pomegranate juice shows antioxidant, antiproliferative, and anti-atherosclerotic properties. The antioxidant capacity (TEAC) of the pomegranate juices was measured using electron paramagnetic resonance (EPR) spectroscopy and 1,1-diphenyl-2-picrylhydrazyl (DPPH•) as a source of free radicals, and the total phenolic (TP) content was measured using UV-Vis spectroscopy. All the examined pomegranate juices exhibited relatively high antioxidant properties. The TEAC values determined by means of EPR spectroscopy using Trolox (TE) as a free radical scavenger were in the range of 463.12 to 1911.91 μmol TE/100 mL juice. The TP content measured by the Folin-Ciocalteu method, using gallic acid (GA) as a free radical scavenger, widely varied in the investigated pomegranate juice samples and ranged from 1673.62 to 5263.87 mg GA/1 L juice. The strongest antioxidant properties were observed with the fresh pomegranate juices obtained from the fruits originating from Israel, Lebanon, and Azerbaijan. Correlation analysis of numerical data obtained by means of EPR spectroscopy (TEAC) and UV-Vis spectroscopy (TP) gave correlation coefficient (r) = 0.90 and determination coefficient (r2) = 0.81 (P <0.05).

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