Study on the Stereoregularity of Polyacrylonitrile Produced by Precipitation Polymerization in Supercritical CO2

Teng, Xinying; Hu, Xuechao; Shao, Huili

doi:10.1295/polymj.34.534

Cited by 7 publications

(7 citation statements)

References 16 publications

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“…As one of the most widely used polymers for textiles and precursors of carbon fibers, polyacrylonitrile (PAN) is prepared commercially by radical polymerization of acrylonitrile (AN), without specific stereoregularity along the chain direction . Since a highly stereoregular PAN is essential to obtain high-tenacity acrylic fibers and carbon fibers, − considerable efforts have been devoted to producing PAN in higher isotactic level. − On the other hand, a number of methods have been developed for the molecular design and controlled synthesis of PAN. − Up to now, completely isotactic PAN (meso/meso triad (mm) >99%) has not yet been obtained. The simultaneous control of the molecular weight and the tacticity for the polymerization of AN has not been attained.…”

Section: Introductionmentioning

confidence: 99%

Radiation-Induced Inclusion Polymerization of Acrylonitrile in Urea Canals: Toward Synthesis of Completely Isotactic Polyacrylonitrile with Controlled Molecular Weight

et al. 2013

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Completely isotactic polyacrylonitrile (meso/meso triad >99%) has been synthesized successfully by radiation-induced inclusion polymerization of acrylonitrile in urea canals. The long-lived nature of the growing radical species and the linear dependence of molecular weight on conversion were observed. The molecular weight distribution of product polymers was relatively narrow (<1.5). The results indicate that the dual control of the molecular weight and the tacticity for inclusion polymerization of acrylonitrile in urea canals is achieved. In addition, the effect of experimental factors of inclusion polymerization on the isotacticity of product polymers was investigated. It is found that to ensure completely isotactic polyacrylonitrile, the following conditions should be met simultaneously: (1) acrylonitrile monomers are included in urea canals totally before γ-ray irradiation, (2) the temperature at the chain propagation step is lower than −90 °C, and (3) the heat of polymerization is removed effectively.

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Section: Introductionmentioning

confidence: 99%

Radiation-Induced Inclusion Polymerization of Acrylonitrile in Urea Canals: Toward Synthesis of Completely Isotactic Polyacrylonitrile with Controlled Molecular Weight

et al. 2013

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“…It has been shown that PAN synthesized in supercritical CO 2 had lower isotacicity than PAN polymerized by other methods, and therefore the PAN homopolymer turned out to be completely random in stereoregularity. 23 (c) Thermal Charaterization. Figures 5 and 6 show the thermogravimetric (TGA) behavior and differential scanning calorimetry (DSC) results on some of the copolymers.…”

Section: Resultsmentioning

confidence: 99%

Copolymerization of Acrylonitrile with Methyl Methacrylate and 2-Chlorostyrene in Supercritical CO₂

Yeo

Kiran

2004

Macromolecules

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Free-radical precipitation copolymerizations of acrylonitrile with methyl methacrylate and 2-chlorostyrene were carried out using AIBN as initiator at 70 °C and 220 bar in carbon dioxide at a total comonomer concentration of 13.6 wt %. Polymerizations were carried out without the use of stabilizers with different feed comonomer molar ratios of 100:0; 98:2; 96:4; 94:6; 90:10; 50:50, and 0:100 acrylonitrile: methyl methacrylate or acrylonitrile:2-chlorostyrene. The preliminary experiments conducted in a view cell showed that these systems that are initially homogeneous solutions undergo phase separation within about 3 h of polymerization time upon formation of polymer chains that are no longer completely miscible in the polymerization medium. Polymerizations that were carried out in a 50 mL high-pressure batch reactor for 20 h under rotational agitation of an impeller at 200 rpm resulted in end products that were either free-flowing powder, or soft solid, or gel (as observed upon depressurization and opening the reactor). The actual physical form was found to be dependent on the initial feed comonomer ratio. Homopolymerization of acrylonitrile led to powders, homopolymerization of 2-chlorostyrene resulted in a soft solid, and homopolymerization of methyl methacrylate resulted in a gel. In the copolymers, those with high acrylonitrile content resulted in powders and became gellike with increasing methyl methacrylate or soft solid with increasing 2-chlorostyrene content. Polymer yield which was about 50% in homopolymerizations was found to decrease in copolymerizations as the acrylonitrile content in the feed mixture was reduced. The number-average molecular weights of the polymers were in the range from 40 000 to 300 000, with polydispersities in the range from 1.4 to 4.8. The polymers were characterized by FTIR, DSC, TGA, 1 H NMR, and 13 C NMR, and the morphologies were evaluated with electron microscopic studies. The acrylonitrile:methyl methacrylate molar ratios in the copolymers as calculated from 1 H NMR were lower than the respective feed comonomer ratios used in their polymerizations. These ratios were even lower in the acrylonitrile-2-chlorostyrene copolymers, suggesting relatively lower reactivity ratios in copolymerizations involving 2-chlorostyrene.

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“…16 1 H NMR (400 MHz, CDCl 3 , δ): 6.41 (s, 1H, CH 2 v), 5.98 (br.s, 1H, NH), 5.87 (s, 1H, CH 2 v), 3.24 (q, 2H, 3 J HH = 6.9 Hz, -NHCH 2 CH 2 -), 3.23 (s, 2H, vC-CH 2 -), 1.49 (quint, 2H, 3 J HH = 7.36 Hz, -NHCH 2 CH 2 CH 2 -), 1.27 (br.m, 10H, -(CH 2 ) 5 CH 3 ), 0.87 (t, 3H, 3 J HH = 6.9 Hz, -CH 3 ); the peaks were assigned relative to the CHCl 3 residual signal at δ = 7.26 ppm. 13…”

Section: Methodsmentioning

confidence: 99%

“…NMR analysis. The 1 H and 13 C NMR analyses were carried out with a Bruker AVANCE 400 spectrometer operating at 400 MHz. The samples were prepared by dissolving 14 to 18 mg of the polymer in 600 μl DMSO-d 6 at 50 °C.…”

Section: Characterizationmentioning

confidence: 99%

“…Researchers have demonstrated that the sequence distributions of PAN obtained via precipitation polymerisation in supercritical CO 2 obeyed the Bernoulli statistics, while its stereo-regularity was completely random; the isotacticity of CO 2 -PAN was lower than that of PAN prepared in water because CO 2 is non-polar. 13 In 2003 Okubo took an AN-CO 2 mixture with a high AN content (up to 25% v/v and more) to perform a precipitation polymerisation in CO 2 . A few experiments with high AN concentrations were carried out; uniform particles were obtained, and the homopolymer formed in high yield.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of polyacrylonitrile copolymers as potential carbon fibre precursors in CO₂

et al. 2014

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Study on the Stereoregularity of Polyacrylonitrile Produced by Precipitation Polymerization in Supercritical CO2

Cited by 7 publications

References 16 publications

Radiation-Induced Inclusion Polymerization of Acrylonitrile in Urea Canals: Toward Synthesis of Completely Isotactic Polyacrylonitrile with Controlled Molecular Weight

Radiation-Induced Inclusion Polymerization of Acrylonitrile in Urea Canals: Toward Synthesis of Completely Isotactic Polyacrylonitrile with Controlled Molecular Weight

Copolymerization of Acrylonitrile with Methyl Methacrylate and 2-Chlorostyrene in Supercritical CO₂

Synthesis of polyacrylonitrile copolymers as potential carbon fibre precursors in CO₂

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Study on the Stereoregularity of Polyacrylonitrile Produced by Precipitation Polymerization in Supercritical CO2

Cited by 7 publications

References 16 publications

Radiation-Induced Inclusion Polymerization of Acrylonitrile in Urea Canals: Toward Synthesis of Completely Isotactic Polyacrylonitrile with Controlled Molecular Weight

Radiation-Induced Inclusion Polymerization of Acrylonitrile in Urea Canals: Toward Synthesis of Completely Isotactic Polyacrylonitrile with Controlled Molecular Weight

Copolymerization of Acrylonitrile with Methyl Methacrylate and 2-Chlorostyrene in Supercritical CO2

Synthesis of polyacrylonitrile copolymers as potential carbon fibre precursors in CO2

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Product

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Copolymerization of Acrylonitrile with Methyl Methacrylate and 2-Chlorostyrene in Supercritical CO₂

Synthesis of polyacrylonitrile copolymers as potential carbon fibre precursors in CO₂