Effect of cross-linker structure on thermal and mechanical properties of poly(methyl methacrylate) networks

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To investigate the impact of cross-linker chemical structure on the thermal and mechanical properties of PMMA, this study designed and synthesized three alkynyl-terminated cross-linkers with distinct structural features: rigid and symmetrical tetra-alkyne pentaerythritol (TPOM), flexible di-alkyne dodecanediol (BD), and tetra-alkyne dodecyldiamine (TDM) featuring both a polar tertiary amine and a flexible chain. These cross-linkers were reacted with azide-terminated four-arm poly(methylmethacrylate) macromonomer ((PMMA-N3)4) via azide-alkyne click chemistry to obtain three PMMA polymer networks with different structures. The resulting cross-linked polymers were thoroughly characterized using 1H NMR, FT-IR, TGA, DSC, and DMA. And the results indicate that the rigidity, flexibility, and polarity of the cross-linkers significantly influence the microstructure of the polymer networks, consequently leading to notable differences in thermal stability, glass transition temperature (Tg), mechanical strength, modulus, elongation at break, and toughness. Specifically, CC-PMMA-TPOM exhibited the highest Tg and storage modulus due to the strong rigidity and compact structure of its cross-linking points. CC-PMMA-TDM demonstrated the highest tensile strength and Young’s modulus, attributed to the physical cross-linking introduced by the tertiary amine groups. Conversely, CC-PMMA-BD achieved a favorable balance between strength and toughness. This work provides molecular-level insights for designing cross-linked PMMA with tailored properties for advanced applications.

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