BEPS is a sulfur-rich diepithio monomer engineered for ultra-high refractive index (n<sub><sup> ≥ 1.70 @ 589 nm) UV/LED-curable optical systems.
Two epithio (thiirane) rings + central disulfide deliver 61 % sulfur by mass, giving:
n<sub><sup> ≈ 1.705 with Abbe number ≈ 23 – ideal for AR/VR pancake lenses, waveguide cores, high-n encapsulants
Dual cure mechanism: ring-opening (cationic) + disulfide addition → shrinkage < 1 %
Compatible with both radical & cationic photoinitiators (TPO, 6976, etc.)
Key Optical & Physical Data:
Refractive index (n<sub><sup>): 1.700 – 1.710
Abbe number (ν<sub>): 23 ± 1
Density: 1.34 g cm⁻³ (20 °C)
Viscosity (25 °C): 35 – 45 mPa·s (easy vacuum casting)
Melting point: < 25 °C (liquid at room temperature)
Volume shrinkage on cure: < 1 % (density dilatometry)
Glass-transition temperature (DSC, 2 % UVI-6976): 155 °C
Typical Formulation Use:
Ultra-high-n lens recipe:
– 60 wt % BEPDS (monomer)
– 38 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 = 162 °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 vapour; use gloves, goggles and adequate ventilation. Store in a cool, dry place away from oxidants and light. SDS available on request.
