Synthesis and characterization of polybenzoxazine–metal hybrids and evaluation of their thermal property

Abstract Polybenzoxazines (PBzs) are a well-established class of phenolic resins synthesized through the thermal ring-opening of benzoxazine monomers, which feature a six-membered heterocyclic ring containing nitrogen and oxygen atoms that act as Lewis base sites in the polymer network. In this study, two conventional PBz systems, poly(2 N-ab) and poly(P-pt), were investigated for their structural and thermal behaviors upon coordination with selected metal ions (Mn 2+ , Th 4+ , and Cd 2+ ). FTIR and XRD analyses confirmed successful metal coordination and structural rearrangements within the polymer matrix. Thermogravimetric analysis (TGA) demonstrated that coordination with Th 4+ significantly enhanced the thermal stability of the PBz hybrids, as evidenced by notable increases in the temperatures at 5% weight loss (Td 5 ) and 10% weight loss (Td 10 ). Specifically, poly(2 N-ab)/Th 4+ exhibited Td 5 and Td 10 values of 294 °C and 448 °C, respectively, markedly higher than 227 °C and 260 °C for the unmodified polymer. Similarly, poly(P-pt)/Th 4+ showed improvements from 150 to 192 °C to 250 and 355 °C. The char yield at 800 °C also substantially increased, rising from 5% to 83% for poly(2 N-ab)/Th 4+ and from 1% to 76% for poly(P-pt)/Th 4+ , indicating enhanced residue formation and thermal robustness. Mn 2+ and Cd 2+ complexes similarly improved the thermal degradation resistance and char yield, although to a lesser extent than Th 4+ . These findings highlight the strong metal–polymer interactions and crosslinking effects that reinforce the thermal integrity of PBz-metal hybrids, making them promising materials for high-performance applications.