Copolymerization and addition of styrene andN-phenylmaleimide in the presence of nitroxide
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The copolymerization and addition reaction of styrene (S) with N-phenylmaleimide (PMI), either neat or in xylene, have been found to proceed at 125°C in the presence of 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO) radicals. TEMPO-terminated alternating S-PMI copolymers and comonomer adducts were obtained. The amounts of the low molecular weight compounds increased with the increasing content of PMI in the initial mixture. The reaction suggests formation of monofunctional unimolecular initiators. In the autopolymerization of neat comonomers, a mediating role of TEMPO was observed. The synthesized copolymers containing TEMPO end groups were used as macroinitiators to initiate polymerization of styrene. The molecular weight distributions of resulting poly(styrene-alt-N-phenylmaleimide)-block-polystyrene copolymers indicated the presence of both low molecular weight termination products and some copolymer precursor. The copolymers and comonomer adducts were characterized using the nitrogen analysis, size-exclusion chromatography (SEC), and NMR spectroscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1093–1099, 2000Keywords:
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Abstract A facile synthesis of linear monodisperse hydroxyl‐containing polystyrene, poly{styrene‐ co ‐[ p ‐(1‐hydroxyethyl)styrene]} and poly{styrene‐ co ‐[ p ‐(2‐hydroxypropan‐2‐yl)styrene]}, was carried out via chemical modification of polystyrene by a two‐step procedure, i. e. monodisperse polystyrene was acetylated under mild conditions, followed by processes of reduction with LiAlH 4 and addition with CH 3 MgBr, respectively. 1 H NMR and FTIR spectra showed that in both cases, the reaction of acetyl to hydroxyl is complete. Sizeexclusion chromatography demonstrated that both molecular weight and monodispersity of the final products were basically unchanged.
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Polystyrene
Chemical modification
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Abstract A series of ethylene‐styrene copolymerizations was carried out in the presence of cyclopentadienyltitanium trichloride and methylalumoxane at 20°C and at different comonomer feed compositions. By sequential extraction a copolymeric material with a styrene units content up to 36 mol‐% can be separated from the homopolymeric products. Some considerations about the relative reactivity of the comonomers and the regioregularity of the styrene insertion are made on the basis of the 13 C NMR spectra.
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The development of stable-radical mediated polymerization (SRMP) from its origins with focus on nitroxide-mediated radical polymerization (NMP) is reviewed. The underlying persistent radical effect, mechanistic steps, fundamental kinetic equations and side reactions of NMP are discussed. The most important nitroxides and alkoxyamine initiators for NMP are presented, along with the parameters influencing the rate constants of cleavage and reformation of alkoxyamines. Applications of NMP for synthesis of complex polymeric structures and in industry are shown, and advances in nitroxide-mediated photopolymerization (NMPP) are discussed. SRMP with the most important non-nitroxide stable organic radicals as well as the organometallic-mediated radical polymerization (OMRP) are briefly mentioned.
Cobalt-mediated radical polymerization
Living free-radical polymerization
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Nitroxide-mediated radical polymerizations (NMP) of styrene at 100 °C using the cationic emulsifier tetradecyltrimethylammonium bromide (TTAB) have been carried out employing 2,2′-azoisobutyronitrile (AIBN) and two nitroxides of different water solubilities. The polymerization rate was lower and the molecular weight distribution more narrow in microemulsion than bulk at low conversion. The results can be rationalized based on the lower initiator efficiency in microemulsion than bulk, presumably caused by the confined space effect (compartmentalization) on geminate termination of AIBN radicals, and possibly also the confined space effect causing an increase in deactivation rate. The extent of retardation relative to bulk was more severe for the less water-soluble 2,2,5-trimethyl-4-phenyl-3-azahexane-3-oxy (TIPNO) than the more water-soluble N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (SG1) as expected based on more extensive nitroxide exit occurring in the case of SG1 than TIPNO. The results illustrate how effects of heterogeneity can profoundly influence the course of NMP in dispersed systems.
Microemulsion
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Compartmentalization (fire protection)
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ABSTRACT An efficient introduction of vinyl group into poly (ethylene‐ co ‐styrene) or poly(ethylene‐ co −1‐hexene) has been achieved by the incorporation of 3,3′‐divinylbiphenyl (DVBP) in terpolymerization of ethylene, styrene, or 1‐hexene with DVBP using aryloxo‐modified half‐titanocenes, Cp′TiCl 2 ( O −2,6‐ i Pr 2 C 6 H 3 ) [Cp′ = Cp*, t BuC 5 H 4 , 1,2,4‐Me 3 C 5 H 2 ], in the presence of MAO cocatalyst, affording high‐molecular‐weight polymers with unimodal distributions. Efficient comonomer incorporations have been achieved by these catalysts, and the content of each comonomer could be varied by its initial concentration charged. The postpolymerization of styrene was initiated from the vinyl group remained in the side chain by treatment with n ‐BuLi. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2581–2587
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1-Hexene
Hexene
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Copolymerization of ethylene and styrene was carried out with CpTiCl3/MgCl2-PMAO as a catalyst at various temperatures and comonomer concentrations. The present catalyst system produces a pseudorandom copolymer of ethylene and styrene beside syndiotactic poly(styrene) (sPS) and poly(ethylene) (PE). The copolymers were obtained at temperature ⪈60°C, indicating the active species promoting the copolymerization being formed at elevated temperatures. On the other hand, styrene incorporation in the copolymer increases progressively with the increase of styrene concentration.
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Copolymerization of ethylene and styrene was carried out with CpTiCl3/MgCl2-PMAO as a catalyst at various temperatures and comonomer concentrations. The present catalyst system produces a pseudorandom copolymer of ethylene and styrene beside syndiotactic poly(styrene) (sPS) and poly(ethylene) (PE). The copolymers were obtained at temperature ⪈60°C, indicating the active species promoting the copolymerization being formed at elevated temperatures. On the other hand, styrene incorporation in the copolymer increases progressively with the increase of styrene concentration.
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ABSTRACT Aryloxo‐modified half‐titanocenes, Cp′TiCl 2 ( O ‐2,6‐ i Pr 2 C 6 H 3 ) [Cp′ = Cp* ( 1 ), t BuC 5 H 4 ( 2 )], catalyze terpolymerization of ethylene and styrene with α‐olefin (1‐hexene and 1‐decene) efficiently in the presence of cocatalyst, affording high‐molecular‐weight polymers with unimodal distributions (compositions). Efficient comonomer incorporations have been achieved by these catalysts. The content of each comonomer (α‐olefin, styrene, etc.) could be controlled by varying the comonomer concentration charged, and resonances ascribed to styrene and α‐olefin repeated insertion were negligible. The terpolymerization with p ‐methylstyrene ( p ‐MS) in place of styrene also proceeded in the presence of [PhN(H)Me 2 ][B(C 6 F 5 ) 4 ] and Al i Bu 3 cocatalyst, and p ‐MS was incorporated in an efficient matter, affording high‐molecular‐weight polymers with uniform molecular weight distributions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2565–2574
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Cyclopentadienyl complex
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Functionalized polyolefins bearing alkoxyamines derived from a nitroxide radical coupling reaction were successfully used as macroinitiators to graft polystyrene or substituted polystyrene brushesvia nitroxide mediated polymerization.
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