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

Abstract

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.

The X-ray investigation of the macro-stresses and design for its realization (laboratory practicum)

“…The MMD of the polymer product was relatively narrow (the polydispersity coefficient is less than 1.5). The results show that double control -MM and tact is simultaneously observed, which, according to the authors of [49], is due to polymerization involving urea. Varying the conditions of polymerization showed that for the synthesis of a fully isotactic PAN, the following conditions must be ensured at the same time: (1) mixing of AN and urea before the start of gamma irradiation,…”

The formation of conjugated structure and its transformation to pseudo-graphite structure during thermal treatment of polyacrylonitrile

“…PAN synthesized through free radical polymerization has an atactic structure; and the isotactic-rich PAN can be obtained by g-ray radiant polymerization in channel complexes of urea. [13][14][15] The neighboring nitrile group on the isotactic units creates conditions favoring the cyclization. 16,17 Coleman et al 18 concluded that the distribution of the tactic placements of the polymer chain limited the cyclization degree, and this result was further confirmed by a computer simulation.…”

High-strength carbon fiber and polymer composites based on acrylonitrile

“…Almost completely isotactic polyacrylonitrile (the proportion of meso-triadiads is > 99%), as well as copolymers of AN, were successfully synthesized by Chinese chemists [49] under conditions of radiation-induced polymerization of acrylonitrile in the presence of urea. In this case, the main signs of "live" controlled polymerization were observed, including the linear dependence of the MM polymer on conversion.…”