Drawing inspiration from the mechanism in copolymers of Polyacrylonitrile (PAN) in the cyclization process, the present study shows the superiority of the Glucaric Acid (GA) and Mucic Acid (MA) incorporated PAN fibers as compared to non-additive incorporated PAN fibers in terms of kinetics of cyclization. To the best of our knowledge, a model-free isoconversional approach was used for the first time to evaluate the activation energies of cyclization for the fiber samples as a function of conversion. The results show almost 5 times lower activation energies of PAN/GA and PAN/MA fibers at the start of the reaction as compared to non-additive incorporated PAN fibers. A kinetic-controlled autocatalytic model was used to evaluate the activation energies of initiation and propagation and the ratio of their corresponding rate constants. GA and MA proved to enhance the ratio of rate constant by almost two orders of magnitude. The pre-exponential factor for the reaction in the constant activation energy regime was accurately evaluated using the model-based approach in combination with the artificial isokinetic relationship. Subsequently, the experimental data points that lie in the diffusion regime were treated with a diffusion-based model that proved that the diffusive rate constant is not only a function of temperature but also reaction conversion.

Cyclization kinetics of polyacrylonitrile/aldaric-acid sugar precursors using isoconversional method

ACS Spring Meeting 2021

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