Spin Trapping by 2-Methyl-2-nitrosopropane (MNP) in the Polymerization of Styrene or Substituted Styrenes and Maleic Anhydride.

The styrene polymerization initiated by benzoyl peroxide (BPO) in the presence of N-tert-butyl-a-isopropylnitrone as nitroxide precursor is well-controlled provided that a prereaction between the nitrone and BPO is carried out in suitable conditions prior to polymerization at a higher temperature. Electron spin resonance (ESR) spectroscopy was implemented to probe the nitroxides formed during both steps, that is, the prereaction and polymerization, and to get crucial information regarding the structure of the nitroxides responsible for the polymerization control. ESR studies combined with first principles calculations have evidenced that nitroxides observed during the prereaction in the presence of styrene and during the polymerization steps consist of a mixture of two macronitroxides. One is formed by the addition of a growing polystyrene chain to the nitrone as would be expected. However, the second one results from the addition of a polystyrene chain to tert-butyl nitroso that is in situ formed presumably by decomposition of the first macronitroxide type.

Section: Resultsmentioning

confidence: 89%

“…We then supposed the possible occurrence of a secondary spin trap species such as tert ‐butyl nitroso ( t‐ BuNO) which can be formed from the degradation of nitroxides 31, 69–73. An evidence was brought by polymerizing styrene with BPO in the presence of t ‐BuNO at 110 °C in place of Nit.…”

Section: Resultsmentioning

confidence: 99%

In situ nitroxide‐mediated polymerization of styrene promoted by the N‐tert‐butyl‐α‐isopropylnitrone/bpo pair: ESR investigations

Detrembleur

Clément

Sciannamea

et al. 2013

“…Additional support for the polar tetramethylene diradical in the case of p ‐methoxystyrene and dimethyl cyanofumarate came from the electron paramagnetic resonance (EPR) spectra of the intermediate with t ‐butylnitroxide (tBuNO) as the spin trap22 and X‐ray crystallography of the 1:1:1 cycloadduct of the two monomers and 2,2,6,6‐tetramethylpiperidine‐ N ‐oxyl (TEMPO) 23. Eberson and coworkers22, 23 showed that the diradical tetramethylene either initiated copolymerization or was trapped by tBuNO or TEMPO at the electron‐rich benzylic position (Scheme ).…”

Section: Spontaneous Initiation Via Tetramethylene Intermediatesmentioning

confidence: 99%

“…Using ESR, Mash et al71 were able to exclude a vinyl radical as a viable contributor. Eberson and coworkers22, 23 carried out comprehensive ESR studies of the reactions of electron‐rich vinyl monomers and found that spin trapping with nitroso compounds gave two types of spectra. The species earlier thought to be a vinyl radical formed from the reaction of the electron‐rich and electron‐poor olefins was actually an oxazinium cation radical, and the purported hydro radical was an oligomeric copolymerizing radical.…”

Section: Revisions Of Earlier Workmentioning

confidence: 99%

Organic and polymer chemistry of electrophilic tri‐ and tetrasubstituted ethylenes

Hall

Padías

2004

135

A survey of the spontaneous reactions of electrophilic olefins and nucleophilic olefins is presented as an area in which organic chemistry merges with polymer chemistry. The products include both small molecules and polymers, arising via tetramethylene biradical zwitterions that can cyclize or initiate polymerizations. Electrophilic tri-and tetrasubstituted olefins are particularly useful in delineating the transition from radical chemistry to ionic chemistry. A periodic table embodying these results enables predictions. Charge-transfer complexes, although observed in many of these reactions, play no significant role. Various aspects arising from these investigations include new cationic initiators, Lewis acid catalysis, quinodimethane chemistry, and photochemistry.

“…However, Eberson and Persson, 18 using cyclovoltammetric data and oxidation/reduction potentials, demonstrated that for energetic reasons ET could only occur in the reactions of extremely electron-rich olefins with extremely electron-poor olefins, as represented in Table III. They explain that only the extremely electron-rich diene 1,4-bis(dimethylamino)-1,3-butadiene, as well as its bicycloheptane analogue, can undergo ET even with the extremely electrophilic tetracyanoethylene (TCNE).…”

Section: Initiation In Spontaneous Ct Polymerizationsmentioning

confidence: 99%

“Charge transfer” polymerization—and the absence thereof!

Hall

Padías

2001

ABSTRACT:Mechanisms for "charge-transfer" spontaneous polymerizations and cycloadditions between electron-rich olefins and electron-poor olefins were reviewed. As for propagation, literature proposals involving chargetransfer complexes were rejected. Instead, alternating copolymerization is ascribed to polar effects in free-radical reactions. As for spontaneous initiation, literature proposals involving charge-transfer complexes, with or without proton transfer, were rejected. Instead, the initiating species is postulated to be a tetramethylene zwitterion biradical, which may initiate either ionic homopolymerization or freeradical copolymerization. A new hypothesis proposes that any interaction that brings vinyl monomers close together may facilitate tetramethylene formation and spontaneous polymerization. These interactions include Coulombic, acidbase, hydrophobic-hydrophilic and templating-tethering interactions.