Controlled radical polymerization of styrene in the presence of molecular iodine

Controlled radical polymerization of styrene in toluene by the RITP method in the presence of I₂ and radical initiators, 2,2′-azobis(isobutyronitrile) and benzoyl peroxide, was studied.

     

Controlled free‐radical polymerization of 2‐vinylpyridine in the presence of nitroxides

Bulk free‐radical polymerization of 2‐vinylpyridine (2VP) in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) was studied under different conditions (temperature and presence of additives). Linear poly‐(2‐vinylpyridine) with a narrow molecular weight distribution and controllable molecular weight was prepared in the presence of acetic anhydride at 95 °C up to a conversion of 66%. At higher conversions side reactions became very important (pseudoliving polymerization). By applying this procedure, well‐defined random copolymers of 2VP with styrene or tert‐butylmethacrylate as well as block copolymers of 2VP with styrene were synthesized. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2889–2895, 2001     

Controlled radical polymerization of styrene in the presence of cyclic 1,2‐disulfides

The thermal polymerization of styrene (St) in the presence of cyclic 1,2‐disulfides at 120 °C was investigated. In the polymerization of St in the presence of 1,2‐dithiane (DT), that is, six‐member cyclic 1,2‐disulfide, the polymer yields and molecular weights increased with the reaction time. The linear relation between the polymer yields and molecular weights was observed, and the line passed through an original point. The molecular weight distributions of the polymers remained almost constant but were not narrow. For this polymerization with a living nature, we proposed the following mechanism: the propagating St radical reacted with thiyl radicals derived from DT, leading to the formation of dormant species, and the formed C S bond of the dormant was dissociated again to give the propagating polystyryl radical and thiyl radical. Similar results were obtained in the thermal polymerization of St at 120 °C in the presence of 1,2‐dithiacycloheptane, that is, seven‐member cyclic 1,2‐disulfide. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 145–151, 2001     

Studies of the radical polymerization of styrene in the presence of polybutadiene

Polymerization of styrene in solutions containing polybutadiene can be used for study of the intermediate stages in the radical polymerization of the monomer.     

Controlled radical polymerization of styrene in miniemulsion polymerization using reversible addition fragmentation chain transfer

Miniemulsion polymerizations of styrene in the presence of two reversible addition–fragmentation chain-transfer (RAFT) agents were studied. The rates were significantly retarded by the presence of a RAFT agents S-(thiobenzoyl)thioglycolic acid, 1, or dithiobenzoic acid 1-phenylethyl ester, 2. Control in miniemulsion polymerization is not as good as for bulk polymerizations. The miniemulsions could also be stabilized against Ostwald ripening by a polymer terminated by a dithiobenzoic moiety. In this case, the polymerization was not controlled because of the generation of renucleated particles. To cite this article: I. Uzulina et al., C. R. Chimie 6 (2003).     

Synthesis of dipolar nitronyl nitroxides

The synthesis of a nitronyl nitroxide radical with a dipolar (mesomeric betaine) unit is reported.     

Controlled radical polymerization in the presence of N‐oxyls

Recent development in controlled radical polymerization has provided a tool to combine a relatively robust radical polymerization technique with structural control. This contribution focuses on stable free radical polymerization in the presence of nitroxides. The influence of 2,2,6,6‐tetramethyl‐piperidine‐N‐oxyl (TEMPO) and temperature on the copolymerization of styrene and acrylonitrile will be discussed. In the second part a new class of nitroxide stable free radicals will be presented that shows enhanced performance in styrene polymerizations.     

Controlled free radical polymerization of styrene initiated from the alkoxyamine-functionalized silicon surface

Manipulation of surface properties of wafer is im- portant in technologies of biotechnology and advanced microelectronics[1,2]. A number of methods have been developed to modify the surface properties[3]. Among them, polymer brush is a well recognized met…     

Electrochemistry of nitronyl and imino nitroxides

Redox potentials of a wide group of azolyl-substituted nitronyl and imino nitroxides were determined by classic cyclic voltammetry (CV). Conclusions have been made for this group of compounds, and their peculiarities were emphasized in comparison with methyl-, phenyl-, iodo-, and cyano-substituted nitroxides.     

p-Quinones in the radical polymerization of styrene

Russian Chemical Bulletin - The polymerization of styrene in the presence of p-quinones of various structures was studied. The polymerization kinetics and molecular weight characteristics of...     

Investigation of the free radical polymerization of styrene in the presence of several 1,1-disubstituted ethylenes

A variety of 1,1-disubstituted ethylenes, having an electron-withdrawing (capto) and an electron-donor (dative) substituent on the same carbon, were synthesized and added to styrene polymerizations. The dative substituents investigated were alkoxy or alkylcarbonate. After the addition of a polystyryl radical to a disubstituted ethylene, the resulting alkoxy or carbonate radicals could potentially fragment, resulting in chain termination and the formation of alkyl radicals. This process is called addition-fragmentation chain transfer (AFCT). The polymers produced during this study were examined for evidence of copolymerization and AFCT. The relative stability of the radicals generated by the fragmentation process appears to be the predominant factor controlling the ratio of copolymerization versus AFCT. © 1993 John Wiley & Sons, Inc.     

Controlled radical polymerization of styrene mediated by dithiobenzoates as reversible addition-fragmentation chain-transfer agents

The radical polymerization of styrene at 60 and 80°C mediated by benzyl dithiobenzoate and poly(styrene dithiobenzoate) as reversible addition-fragmentation chain-transfer agents has been studied. It has been shown that both agents are characterized by high chain-transfer constants and provide control over molecular-mass characteristics of polymerization products. The number-average molecular mass of polystyrene linearly grows with conversion, and the polymers are characterized by low values of polydispersity indexes. It has been demonstrated that the rate of polymerization significantly decreases with an increase in the concentration of reversible addition-fragmentation chain-transfer agents. This effect is typical of styrene polymerization mediated by dithiobenzoates. The possible reasons for this phenomenon are discussed.     

Microwave-assisted nitroxide-mediated radical polymerization of styrene

The first single-mode microwave-assisted nitroxide-mediated radical polymerizations (NMRP) of styrene in bulk were successfully performed. The results showed that the polymerization proceeded in a controlled way. The power of microwave irradiation has considerable effect on the polymerization rate. The polymerization rates under appropriate power of microwave irradiation were faster than that under conventional heating (CH) at the same polymerization temperature. The living nature of the polymer was proved by successful chain extension polymerization and ¹H NMR spectrum analysis.     

Specifics of radical polymerization of styrene and methyl methacrylate in the presence of ruthenium carborane complexes

The specifics of the radical polymerization of styrene and methyl methacrylate in the presence of ruthenium closo- and exo-nido-carborane complexes with phosphine and diphosphine ligands were investigated. It was shown that, depending on a coinitiator, the polymerization proceeds through the atom transfer radical mechanism or the reverse atom transfer radical mechanism to high conversions without gelation to yield macromolecules with a low polydispersity. The influence of the ligand environment, the oxidation state of ruthenium atoms in the carborane complexes, and the temperature conditions on the specific features of the polymer synthesis was established.     

Mechanism of the controlled radical polymerization of styrene and methyl methacrylate in the presence of dicyclopentadienyltitanium dichloride

The mechanism of the controlled radical polymerization of styrene and methyl methacrylate in the presence of dicyclopentadienyltitanium dichloride (Cp₂TiCl₂) was studied using quantum chemical calculations and electron spin resonance spectroscopy. It was established that the reduction of Cp₂TiCl₂ to Cp₂TiCl during the macromolecule synthesis occurs through the living polymerization mechanism, which adjusts the growth of a polymeric chain. The geometrical structures of the molecular complexes between a growing macroradical and Cp₂TiCl₂ and transition states of radical inhibition steps were optimized and the thermodynamic and kinetic parameters of the elementary reactions were estimated for several feasible directions of the process. On this basis, the observed kinetic features of vinylic monomer polymerization with participation of organic compounds of titanium are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Anionic polymerization of styrene in the presence of pyridine

An interesting effect of pyridine on the anionic polymerization of styrene in THF is described. Pyridine forms a complex with living polystyrene and greatly slows the polymerization rate without changing the degree of polymerization. From kinetic and spectroscopic studies, it was clear that there exist two active species in this system and the complex between living polystyrene and pyridine was of the 1:1 type, which itself had a weak ability to grow. The formation constant of the complex K was found to be about 4 × 10⁵ l./mole. The effect of substituted pyridine was also studied and the nature of the complex was discussed.     

1,3-Dipolar cycloaddition in the synthesis of pyrazolyl-substituted nitronyl nitroxides

A new approach to the synthesis of polyfunctional pyrazolyl-substituted nitronyl nitroxides was developed based on the presynthesized pyrazole derivatives prepared by 1,3-dipolar cycloaddition. The structures of the resulting mono-and biradicals were confirmed by X-ray diffraction. Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2105–2116, September, 2005.     

A new method for the reduction of nitronyl nitroxides

Reduction of nitronyl nitroxides using hexamethylenetetramine is a very convenient method for preparing the corresponding imino nitroxides and 2-imidazoline N-oxides.