Bis(2,3-epithiopropyl) disulfide is a sulfur-rich heterocyclic monomer engineered for high-refractive-index (RI ≥ 1.72 @ 589 nm, 25 °C) UV/LED-curable optical systems.
Each molecule carries two epithio (thiirane) rings and a disulfide bridge, providing:
Very high sulfur content (60.9 % w/w) → n<sub><sup> ≈ 1.72 while maintaining Abbe number ≈ 24
Dual cure mechanism: ring-opening of thiiranes (cationic or anionic) + disulfide radical addition → low shrinkage (< 1.5 %)
Key Optical & Physical Data:
Refractive index (n<sub><sup>): 1.715 – 1.725
Abbe number (ν<sub>): 24 ± 1
Density: 1.43 g cm⁻³ (20 °C)
Melting point: 46 – 50 °C (low-melt, suitable for precision moulding)
Viscosity (60 °C): 12 – 16 mPa·s (easy vacuum casting)
Volume shrinkage on cure: < 1.5 % (density dilatometry)
Glass-transition temperature (DSC, 3 % CPI-976M): 152 °C
Bis(2,3-epithiopropyl) disulfide
UV-Curable Materials, High refractive index monomer
Synonyms: BEDS
CAS No.: 98485-71-3
Purity: ≥98% (GC)
Refractive Index:1.72
Appearance: Colourless to light-yellow low-melting solid; faint sulfurous odour.
