Radical polymerization of acrylonitrile initiated by a-picolinium p-chlorophenacylid (original) (raw)
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Solvent effects on the heterogeneous radical polymerization of acrylonitrile
Polymer Bulletin, 1982
The heterogeneous radical polymerization of acrylonitrile was carried out in various solvents. The apparent rates and degrees of polymerization decreased in the presence of basic solvents such as alcohols, ethers and amines. The acrylonitrile radical does not readily abstracts an acidic q-hydrogen from solvents such as alkyl nitriles, indicating that the polar effect is more important than resonance stabilization of the resulting radical. Solvation of the electron defficient polyacrylonitrile radical by basic solvents is proposed.
2001
Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208 016, India <em>E-mail</em> : sskatiyar@yahoo.com <em>Fax</em> : 91-512-570006 <em>Manuscript received 3 November 2000</em> Homopolymerization of acrylonitrile, initiated by <em>p</em>-nitrophenacyldimethyl sulfonium ylide has been studied at 40<sup>o</sup> under inert atmosphere using dilatometric technique. The radical polymerization of acrylonitrile follows non-ideal kinetics, since the monomer and initiator exponent values are found to be 1.1 and 0.39, respectively. The polymerization is retrarded by hydroquinone. The overall activation energy is calculated to be 44 kJ mol<sup>-1</sup>• Kinetic data indicate that the polymerization involves free radical mechanism.
European Polymer Journal, 2009
Living radical polymerizations of acrylate are known to be difficult to achieve using TEMPO as a mediator. The stable free radical polymerization (SFRP) of acrylate tends to stop at low monomer conversion due to the accumulation of TEMPO in the medium as a result of unavoidable bimolecular termination. Rather than solving this problem by destroying the excess nitroxide using ascorbic acid or glyceraldehyde associated with pyridine as reported recently, high temperature initiators were used to slowly and continuously generate new radicals throughout the polymerization to consume the excess TEMPO molecules. Polymerizations of n-butyl acrylate initiated by the alkoxyamine unimer (1benzoyloxy)-2-phenyl-2-(2 0 ,2 0 ,6 0 ,6 0-tetramethyl-1 0-piperidinyloxy)ethane (BST) were performed between 130°C and 134°C in the presence of a series of high temperature peroxide and azo initiators. The best results in this study were obtained by the continuous addition of small amounts of di-tert-amyl peroxide throughout the polymerization. Under these conditions, the acrylate polymerizations fulfilled the criteria of a controlled polymerization process although the molecular weight distributions were slightly broad (M w /M n $ 1.5).
Chemistry-a European Journal, 2008
The successful controlled homopolymerization of acrylonitrile (AN) by cobalt-mediated radical polymerization (CMRP) is reported for the first time. As a rule, initiation of the polymerization was carried out starting from a conventional azo-initiator (V-70) in the presence of bis(acetylacetonato)cobalt(II) ([Co(acac)2]) but also by using organocobalt(III) adducts. Molar concentration ratios of the reactants, the temperature, and the solvent were tuned, and the effect of these parameters on the course of the polymerization is discussed in detail. The best level of control was observed when the AN polymerization was initiated by an organocobalt(III) adduct at 0 °C in dimethyl sulfoxide. Under these conditions, poly(acrylonitrile) with a predictable molar mass and molar mass distribution as low as 1.1 was prepared. A combination of kinetic data, X-ray analyses, and DFT calculations were used to rationalize the results and to draw conclusions on the key role played by the solvent molecules in the process. These important mechanistic insights also permit an explanation of the unexpected “solvent effect” that allows the preparation of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) by CMRP.
Redox Polymerization of Acrylonitrile
The kinetics of polymerization of acrylonitrile initiated by the redox systems cyanoacetic acid/Mn(OAc)3 and cyanoacetic acid/tris(benzoylacetonato)manganese(llI) in dimethylsulphoxide as solvent have been investigated over the range 20-35L The kinetics of oxidation are consistent with the formation of intermediate complexes between the reactants, followed by electron transfer. Manganous ions inhibit the reaction by competitive complexation. The primary radicals are very efficient as initiators of polymerization which is terminated by mutual interaction of macroradicals. Mechanisms have been proposed to explain the kinetics; rate and equilibrium constants have been evaluated.
2021
The termination mechanism in the radical polymerization of acrylonitrile (AN) was determined by the reaction of structurally well-defined polyacryronitrile (PAN) chain-end radical 1a and PAN-end mimetic small model radical 1b. The contributions of three mechanisms, i.e., the disproportionation (Disp), the combination by carbon-carbon formation (CC-Comb), and the combination by carbon-nitrogen bond formation (CN-Comb), were unambiguously determined. The CN-Comb pathway was experimentally proved for the first time. The selectivity between Disp and CC-Comb showed a good correlation with the viscosity and temperature, and the Disp selectivity increased as the viscosity increased, as previously reported for the termination of other monomers. In contrast, CN-Comb is insensitive to viscosity but sensitive to polarity; the selectivity decreases as the polarity of the media increases. The results strongly suggest the presence of two domains in the termination reaction, namely, the polarity- ...
College & Research Libraries, 2019
In this work, the kinetics and mechanism of free radical polymerization of acrylonitrile (AN) using potassium peroxydisulphate (PDS-K2S2O8) as a water soluble initiator in the presence of synthesized 4,4'-dihexadecyl-1,1'-bipyridine diiumdichloride (DHBPDDC) as multi-site phase-transfer catalyst (MPTC) has been investigated. The polymerization reaction were carried out under nitrogen atmosphere and unstirred condition at constant temperature 60+1°C in ethyl acetate/water biphasic medium. The effects of variation of monomer(AN), initiator(PDS) and catalyst(MPTC) solvent polarity and temperature on the rate of polymerisation (Rp) were ascertained. The order with respect to monomer(acrylonitrile) was found to be unity. The order with respect to initiator and catalyst was found to be 0.51, 0.48 respectively. However, an increase in the polarity of the solvent has slightly increased the rate of polymerization value (Rp). Based on the results obtained, a suitable kinetic mechanism...
Fullerene as radical inhibitor in polymerization of acrylonitrile initiated by arsonium ylide
Polymer Science Series B, 2012
Kinetics of polymerization of acrylonitrile (AN) in presence of fullerene (C 60 ) has been studied using p acetyl benzylidine triphenyl arsonium ylide as initiator in dioxane at 60 ± 0.1°C under the blanket of nitrogen. The rate of polymerization (R p ) at low concentration of fullerene may be represented as R p ∝ [Ylide] 0.5 [AN] 1.0 [Full] -0.6 , indicating inhibition effect of fullerene on the polymerization. The energy of activation for the polymerization was found to be 71.5 ± 0.5 kJ mol -1 . Fourier transform infrared spectro scopic analysis (FTIR) confirmed the insertion of fullerene in to the final polymer. The mechanism for the polymerization has also been proposed.