The review summarizes recent advances in the production of carbon fiber precursors based on melt-spun acrylonitrile copolymers. Approaches to decrease the melting point of polyacrylonitrile and acrylonitrile copolymers are analyzed, including copolymerization with inert comonomers, plasticization by various solvents and additives, among them the eco-friendly ways to use the carbon dioxide and ionic liquids. The methods for preliminary modification of precursors that provides the thermal oxidative stabilization of the fibers without their melting and the reduction in the stabilization duration without the loss of the mechanical characteristics of the fibers are discussed. Special attention is paid to different ways of crosslinking by irradiation with different sources. Examples of the carbon fibers preparation from melt-processable acrylonitrile copolymers are considered in detail. A patent search was carried out and the information on the methods for producing carbon fibers from precursors based on melt-spun acrylonitrile copolymers are summarized.

Amphiphilic narrow dispersed copolymers of acrylic acid and fluoroalkyl acrylates are synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization using dibenzyl trithiocarbonate in DMF solution. These copolymers and polyacrylic acid containing the trithiocarbonate group within the polymeric chain are used for the synthesis of triblock copolymers in organic, aqueous–organic or aqueous media by chain extension with n-butyl acrylate or its mixture with fluoroalkyl acrylates. Both dispersion polymerization and emulsifier-free emulsion polymerization lead to self-assembling of triblock copolymers in the core–shell particles; the former route provides the formation of microstructured polymer films with a percolated structure.

The influence of introducing acrylic acid (AA) into the reaction mixture with acrylonitrile at the synthesis of copolymers by free-radical polymerization (FRP) and radical polymerization with reversible addition–fragmentation chain transfer (RAFT) on the rheological properties of their solutions in dimethyl sulfoxide, as well as on the capability to spin fibers by the mechanotropic method, is analyzed. The influence of AA dosing conditions on the rheological properties of the solutions in the concentration range above the crossover point was not revealed. In the case of RAFT synthesis, the rheological properties differ distinctively in the high concentration region that is expressed by unusual viscoelastic characteristics. Dilute solution viscometry revealed the influence of the comonomer loading order on the interaction intensity of the copolymer macromolecules with a solvent, which is more pronounced for samples synthesized by FRP and can be associated with the copolymers’ molecular structure. Fiber spinning from solutions of polyacrylonitrile and its copolymers (PAN) synthesized by the RAFT method was not able to achieve a high degree of orientation drawing, while for polymers with a wider molecular weight distribution synthesized by FRP, it was possible to realize large stretches, which led to high-quality fibers with strength values up to 640 MPa and elongation at a break of 20%.

The copolymers of acrylonitrile and acrylic acid are synthesized for the first time by trithiocarbonate-mediated reversible addition-fragmentation chain transfer polymerization in DMSO at a content of comonomers in the reaction mixture of 40%. Various regimes of acrylic acid introduction into the reaction are tested. This makes it possible to synthesize copolymers with close average composition and different unit distribution in a chain. It is shown that, with an increase in the fraction of acrylic acid in the copolymer, the contribution of the ionic mechanism of cyclization grows, which is favorable for widening the temperature interval of cyclization and decrease in the intensity of heat flow. Reduction in the rate of introduction of acrylic acid into copolymerization and, as a consequence, its more uniform distribution in the chain lead to analogous effects and cause a decrease in the activation energy of cyclization by both the ionic and radical mechanism. Thus, the use of reversible addition-fragmentation chain transfer polymerization with the dosed introduction of the comonomer allows one to tune the properties of the copolymers during their heat treatment.