Modeling of Living Cationic Ring-Opening Polymerization of Cyclic Ethers: Active Chain End versus Activated Monomer Mechanism

Document Type: Research Article

Authors

1 Nanotechnology Research Center, Urmia University, Urmia, I.R. IRAN

2 Institute of Chemical Research and Technology, Tehran, I.R. IRAN

3 Institute of Chemical Research and Technology, Tehran, I. R. IRAN

4 Nanochemistry Department, Institute of Nanotechnology, Urmia University, Urmia, I.R. IRAN

5 Department of Chemistry, Payame Noor University (PNU), Tehran, I.R. IRAN

Abstract

Living cationic ring-opening polymerization of cyclic ethers in the presence of diol was modeled using method of moments. A widespread kinetic model was developed based on the previous experimental studies. Then, moment and population balance of reactants were obtained. Modeling results were employed to study the influence of initiator and water amounts (as the impurity) as well as feeding policy in polymerization kinetics and final properties of polymer. In addition, sensitivity of modeling results to initiation, backbiting and finally propagation via activated monomer reactions were investigated. Results showed the population of chains is the function of their precursors. In a typical polymerization, chains with diol functionality are the majority. Therefore, most of polymerized monomers are incorporated into those chains. This makes the chains with diol functionality as the determining group in molecular weight distribution (MWD). The kinetics of polymerization and properties of reactor product are highly dependent on the ratio of the rate of propagation via Activated monomer (AM) mechanism to the rate of propagation via active chain end (ACE). Increase in this ratio decreases the probability of occurrence of backbiting reaction. Therefore, cyclic dimers are less formed and MWD narrows. On the other hand, decreasing this ratio results in less diol reacted with protonated monomers. Consequently, the rate of regeneration of initiator and hence the rate of polymerization is decreased. These findings give complete facts about the ring-opening syntheses of polyethers and are valuable for evolving new grades as well as optimization current processes.

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