Novel Potential Precursor of Carbon Fiber Based on Copolymers of Acrylonitrile, Acrylamide, and Alkyl Acrylates

Controlled synthesis of terpolymers of acrylonitrile with acrylamide and alkyl acrylate of similar composition but differing in the alkyl substituent (methyl, butyl, 2-ethylhexyl, and lauryl) has been performed for the first time via the reversible addition-fragmentation chain transfer polymerization under the action of dibenzyl trithiocarbonate. Investigation of thermal behavior of the terpolymers under inert atmosphere has allowed determination of the activation energy of the ionic cyclization as of ~80 kJ/mol irrespectively of the alkyl acrylate nature. Mechanism of chemical transformations of the terpolymers under isothermal treatment at 250°C has not differed from this known for the binary acrylonitrile–acrylamide and acrylonitrile–alkyl acrylate copolymers. At the same time, the rate of the polyconjugated structure formation has been higher in comparison with the analogous terpolymers with acrylic acid. The rate of the stabilization has changed along the following series of alkyl acrylates: methyl acrylate < butyl acrylate ≈ 2-ethylhexyl acrylate < lauryl acrylate. Concentration ranges of the dilute, semidilute, and concentrated solutions have been determined for the synthesized terpolymers.