Polymers find widespread applications in diverse sectors such as building materials, aerospace, and flexible devices, owing to their outstanding processability that translates into substantial economic advantages. Nonetheless, several intrinsic limitations impede their progressive development, encompassing inadequate flame retardancy, brittleness, and resistance to aging. Conventional additives employed to address these challenges remain constrained by single-functionality, high additive concentrations, and the antagonistic effects of different additives. Therefore, this paper presents the development of a series of porphyrin-based multifunctional additives aimed at augmenting the overall performance of polymers. The specifics are elucidated below:

1. 5,10,15,20-tetrakis(4-bromophenyl) porphyrin (TBPP) and zinc 5,10,15,20-tetrakis(4-bromophenyl) porphyrin (Zn-TBPP) were synthesized as multifunctional additives for fabricating high-performance polystyrene (PS) composites. Both TBPP and Zn-TBPP showed high thermal stability and excellent UV-absorption, which significantly enhanced the UV-resistance of PS without sacrificing mechanical property after 100 h UV-aging. The addition of 5 wt% Zn-TBPP led to the remarkable improvement of thermal stability of PS (41 °C and 79 °C increases in the thermal decomposition temperature at 5 wt% mass loss under N2 and air, respectively). Moreover, contributed from the strong π-π interaction between porphyrins and PS chains, the mechanical properties of PS were enhanced when 5 wt% Zn-TBPP was added into PS. Furthermore, compared to TBPP/PS, Zn-TBPP/PS exhibited an improved flame retardant performance with 26.0%, 14.4% and 31.5% reduction of PHRR, PCOP and PCO2P respectively, indicating the catalytic flame retardant effect from zinc element.

2. Epoxy resins (EPs) with excellent toughening and remarkable fire-retarded efficiency are highly demanded. A novel phosphorus-containing porphyrin (PPR) was synthesized to address the poor flame retardancy, thermal and mechanical properties of EP. Incorporating PPR can effectively enhance the glass transition temperature and improve the thermodynamic properties of EP. Meanwhile, PPR exhibits a significant toughening effect of EP with the enhancement of 59.5% of elongation at the break without any stress sacrifice. Moreover, the loading of 5 wt% PPR leads to the UL-94 V-0 rating for EP, while the peak heat release rate and peak smoke release rate are reduced by 44.3% and 22.2%, respectively, indicating the distinguished flame retardant properties.

3. A vanillin-based biomass porphyrin (VPR) was designed and synthesized to efficiently improve the mechanical, anti-UV, and fire retarded properties of Polylactic acid (PLA). Owing to the strong intermolecular interaction, incorporating 3 wt% VPR endows PLA with a significant toughening effect. Compared to pure PLA, the elongation at break and impact strength for PLA/3VPR were improved by 88.2% and 104.2% respectively without any sacrifice of tensile strength. Meanwhile, the PLA/VPR biocomposites exhibited a significantly improved anti-UV performance with only 1.5% and 8.6% decrease of the strength and elongation at break respectively. More importantly, by incorporating only 3 wt% VPR loading, excellent self-extinguishing properties and UL-94 V-0 level were achieved for the PLA/3VPR composite, which greatly improved the versatility of PLA. Overall, the incorporation of bio-based VPR into PLA promotes multifunctional features which could extensively broaden the applications of PLA composites.