What is the polymerization mechanism of polyacrylonitrile?

The Polymerization Mechanism of Polyacrylonitrile

Polyacrylonitrile, commonly known as PAN, is a versatile synthetic polymer formed through a process called free radical addition polymerization. To kickstart this reaction, chemical initiators are introduced. Commonly used substances for this role include azobis(isobutyronitrile) (often called AIBN), benzoyl peroxide, and various persulfates. These initiators break apart to create free radicals, which then attack the acrylonitrile monomer units and link them together in a long chain.

While homopolymers of PAN are tough and strong, they can be notoriously difficult to dissolve and dye, which poses a challenge when manufacturing textile fibers. To overcome this hurdle, chemical engineers frequently introduce comonomers during the reaction. By incorporating these extra components into the polymer backbone, the resulting material gains much better solubility in common spinning solvents like dimethylformamide. Furthermore, these comonomers significantly improve how well the final fibers can absorb and hold dyes, making PAN much more practical for commercial applications like clothing, outdoor tents, and carbon fiber precursors.