Vitrimers undergoing dynamic bond
exchange enable reprocessing
and recycle of thermosets. However, vitrimers are susceptible to creep,
leading to their poor dimensional stability, which limits their applications.
Here, a facile method via integration of metal complexes was utilized
to address this issue, and cross-linked polyimine was selected as
an example of vitrimer. Three different metal complexes were introduced
into a polyimine vitrimer via a one-pot preparation involving the
formation of metal complexes and cross-linking of polyimine. The addition
of 0.5 mol % Cu2+ relative to imine bond reduced creep
degree from 30% to 20% at 60 °C, and the creep resistance was
enhanced with increasing Cu2+ content. Loading 5 mol %
Cu2+ increased the initial creep temperature from 60 to
about 100 °C and raised the Arrhenius activation energy (E
a) for stress relaxation from 52.3 to 67.7 kJ
mol–1. The ability of different metal complexes
to suppress creep followed the order of Fe3+ > Cu2+ > Mg2+, and the initial creep temperature
reached around
120 °C for vitrimer with 5 mol % of Fe3+. Meanwhile,
the polyimine–metal complex vitrimers still exhibited excellent
reprocessing recyclability. Moreover, the introduction of coordination
structures enhanced the thermal and mechanical properties, solvent,
and acid resistance. Thus, metal coordination is an efficient approach
to achieve high-temperature creep resistance, excellent thermal and
mechanical properties, and chemical stability for vitrimers based
on the Schiff base.
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