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
Typical Formulation Use:
High-n lens recipe example:
– 65 wt % Bis(2,3-epithiopropyl) disulfide (monomer)
– 33 wt % divinyl-benzene (cross-linker, n = 1.62)
– 2 wt % UVI-6976 → UV-LED cure (365 nm, 1 J cm⁻²)
→ Cured film: n = 1.738 @ 589 nm; Tg = 160 °C; yellowness index < 1.
Quality Specification (Optical Grade):
Purity (GC): ≥ 98 %
Colour (Pt-Co): ≤ 30
Water content (KF): ≤ 0.1 %
Metal ions (ICP-OES): Na⁺, K⁺, Ca²⁺, Fe³⁺ each ≤ 0.5 ppm
Transmittance (400 nm, 1 cm cell): ≥ 96 %
Hazard Statement:
Causes skin and eye irritation (H315 + H319); harmful if swallowed (H302). Avoid inhalation of dust/vapour; use gloves, goggles and adequate ventilation. Store in a cool, dry place away from oxidants and light. SDS available on request.
