Vitrimer Transition Temperature Identification: Coupling Various Thermomechanical Methodologies
Amber M. Hubbard, Yixin Ren, Dominik Konkolewicz, Alireza S. Sarvestani, Catalin R. Picu, Gary S. Kedziora, Ajit K. Roy, Vikas Varshney, Dhriti Nepal
Abstract
Vitrimers hold great promise as adaptive materials capable of shape reconfigurability, welding, and self-healing due to dynamic covalent reactions occurring above the vitrimer transition temperature (Tv). Previous literature reports the Tv as one value influenced mainly by chemistry; however, literature also reports significant inconsistencies when measuring or identifying Tv trends. Herein, we present unique data interpretation methods to analyze stress–relaxation and elongational creep results allowing for excellent agreement between multiple Tv measurement methodologies. We also demonstrate that experimental parameters (e.g., heating rate and applied axial force) and catalyst concentration are crucial in dictating the Tv range. Varying the catalyst concentration or sample heating rate shifts the Tv up to 115 and 43 °C, respectively. Additionally, we present a kinetic model confirming the temperature dependence of the transesterification rate-limiting step, exhibiting excellent agreement with experimental data. Fundamentally understanding the Tv will inform future design of vitrimers toward applications ranging from recyclable actuators to structural adhesives.