<br/>Recently, due to the covalent adaptive network (CAN), thermoset vitrimer polymers have shown tremendous promise for structural applications such as reshaping and remolding. The trans-esterification reaction plays a vital role in the CAN mechanism, in which the efficiency of the reaction is controlled by organic or organometallic catalysts. Understanding the mechanistic insights of the trans-esterification reaction in the bulk phase is difficult due to the highly crosslinked complex structure of thermosetting vitrimers. In this work, we employ density functional theory (DFT) to investigate catalytic efficiency and the mechanism of the trans-esterification reaction using transition state theory with model systems that include alkoxy and carboxylic groups as reacting sites for mimicking the trans-esterification reaction. The catalytic efficiency of a number of catalysts, including triazabicyclodecen (TBD), dibutyltin dilaurate (DBTL), dibutyltin oxide (DBTO), zinc acetate Zn(OAc)2, zinc acetylacetonate Zn(acac)2, and tin(II) 2-ethylhexanoate (T2EH), is explored. We found that the energy difference between the frontier orbitals in electron donor-acceptor complexes including the catalyst is important. Specifically, the energy difference between the HOMO of the electron donating species and the LUMO of the electron acceptor correlates with the efficiency, where smaller gaps are observed for the more efficient catalysts as measured from experiments than that of larger gaps. The mechanism of trans-esterification reactions for Lewis acids and bases will be discussed based on results from transition state theory

Understanding catalytic efficiency and the mechanism of trans-esterification in vitrimer polymers using density functional theory

2019 Fall National Meeting

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