Catalytic effect of rare-earth triflates in the relaxation and creep behavior of poly(epoxy imine) vitrimers

The catalytic activity of scandium triflate, known for its efficiency in transimination reactions, as well as lanthanum and ytterbium triflates, was explored in promoting imine metathesis reactions in Covalent Adaptable Networks (CANs). In the present work, we focused on a previously examined system where bisphenol A diglycidyl ether (DGEBA) was cured with a telechelic primary amine-terminated polyimine oligomer. The resulting material exhibited vitrimeric behavior ascribable to the imine metathesis reaction. The structure of the oligomer was characterized by 1 H NMR and its molecular weight was determined by end-groups analysis, after derivatization with tert -butyl isocyanate. To overcome the limitations in the stress relaxation process, caused by the network structure, we explored the addition of some rare-earth triflates to see if they could accelerate the exchange process. Fourier-transform infrared (FTIR) spectroscopy confirmed the absence of by-product formation during the curing process with these catalysts, while differential scanning calorimetry (DSC) was used to assess their potential effects on curing kinetics. Thermomechanical properties were evaluated through dynamic thermomechanical analysis (DMTA). Our findings revealed a complex effect of the triflate salts on the creep resistance of the materials. These catalysts enhanced deformation stability through imine-metal coordination but simultaneously reduced activation energies for the exchange process, balancing structural integrity with dynamic adaptability. • Vitrimers have been obtained by polycondensation of DGEBA with a polyimine oligomer. • Rare-earth triflates have been used to catalyze polyimine metathesis. • 1 H NMR spectroscopy has been used to determine the molecular weight of the oligomer. • The addition of La(OTf) 3 produced the highest reduction in the E a of the exchange process. • Yb(OTf) 3 exhibited the lowest creep rate, and reduced residual deformation.