Systems for producing M yarns, wherein M1, include N extruders, M spin stations, and a processor, wherein N>1. Each extruder includes a thermoplastic polymer having a color, hue, and/or dyability characteristic, which are different from each other. Each spin station produces one yarn comprising at least one bundle of filaments. Each spin station comprises at least one spinneret through which filaments are spun from at least two molten thermoplastic polymer streams received by the respective spin station and N spin pumps upstream of the spinneret for the respective spin station. Each spin pump is paired with one of the N extruders. The processor is in electrical communication with the N*M spin pumps and is configured to adjust the volumetric flow rate of the polymers pumped from each spin pump to achieve a ratio of the polymers to be included in each M yarn.

A polyacrylonitrile homopolymer, wherein the homopolymer has a number average molecular weight of from about 50,000 to about 1,000,000 g/mol, as measured by gel permeation chromatography, and a polydispersity index of from about 1.0 to about 1.5. Also disclosed is a method of making a polyacrylonitrile homopolymer, comprising mixing a)-c) to form a mixture: a) an amount of an acrylonitrile monomer; b) an amount of a chain transfer agent, and c) an amount of an aqueous solution comprising one or more components selected from the group consisting of an inorganic salts, organic salts, transition metals, and one or more organic solvents; and
polymerizing the mixture via photo-iniferter reversible addition-fragmentation chain transfer (PI-RAFT) polymerization.

A polyacrylonitrile homopolymer, wherein the homopolymer has a number average molecular weight of from about 50,000 to about 1,000,000 g/mol, as measured by gel permeation chromatography, and a polydispersity index of from about 1.0 to about 1.5. Also disclosed is a method of making a polyacrylonitrile homopolymer, comprising mixing a)-c) to form a mixture: a) an amount of an acrylonitrile monomer; b) an amount of a chain transfer agent, and c) an amount of an aqueous solution comprising one or more components selected from the group consisting of an inorganic salts, organic salts, transition metals, and one or more organic solvents; and
polymerizing the mixture via photo-iniferter reversible addition-fragmentation chain transfer (PI-RAFT) polymerization.