Synthesis and characterization of a new 2-iminothiolate-modified dimethacrylate monomer with potential dental applications

Abstract

A 2-iminothiolate-functionalized dimethacrylate monomer (Bis-[GMA–TBA]) was rationally engineered to modulate network architecture and reduce polymerization shrinkage in methacrylate-based systems. The monomer was synthesized from bisphenol A-glycidyl methacrylate (Bis-GMA) through a sequential Mitsunobu azidation, Staudinger reduction, and post-functionalization with 2-iminothiolane. Structural integrity and successful side-chain incorporation were confirmed by FT-IR, ¹H NMR, and ESI-MS analyses. Photocurable matrices containing 50 wt% Bis-[GMA–TBA]/TEGDMA were formulated to evaluate structure-property relationships relative to conventional Bis-GMA/TEGDMA systems. The modified formulation exhibited a volumetric shrinkage of 8.2%, representing a ∼27% reduction compared to the reference system (11.3%). Notably, this shrinkage reduction was achieved without compromising mechanical performance, as shear bond strength values remained comparable (55 ± 1.7 N vs. 49 ± 1.2 N), and marginal microleakage showed no significant differences. The reduced shrinkage is attributed to increased free volume and steric hindrance introduced by the bulky iminothiolate moiety, which modulates crosslink density and polymer network packing. These results demonstrate that targeted side-chain engineering provides an effective molecular strategy to tailor polymerization behavior while preserving mechanical integrity. This approach offers a versatile platform for the development of next-generation functional methacrylates for advanced biomedical materials.