Vitrimeric behavior revealed by fast scanning calorimetry in branched polyglycerol networks crosslinked by reversible enamine bonds

This document is the unedited author's version of a manuscript submitted for publication in Macromolecules after peer review.

Abstract: Dynamic covalent bonds formed by enamine have played a crucial role in the development of vitrimers by enabling their rearrangement and reprocessability. In this study, polymer networks obtained by crosslinking a b-ketoester-functionalized branched polyglycerol (PG-bkest) with three different diamines, i.e. diaminopropane (DAP), 2,2′-(ethylenedioxy)bis(ethylamine) (EDO) and Jeffamine D230 (Jeff) were generated through enamine bond formation enabling the formation of materials with tunable glass transition temperatures (T_g). A single, though broad, specific heat step was detected in all cases by conventional differential scanning calorimetry (DSC). However, by judiciously varying thermal protocols using fast scanning calorimetry (FSC), which permits heating/cooling rates as large as 1000 Ks^-1, we were able to separate and identify two distinct thermal events in the network composed by Jeff, used as a vitrimeric network model. Using Kissinger analysis, we conveyed information about the apparent activation energies of the two thermal events. In such a way, we were able to provide compelling evidence that the high-temperature event is due to a vitrimeric transformation (T_v), while the low-temperature event exhibits all the features of a conventional glass transition.