Sulfur-Rich Norbornadiene-Derived Infrared Transparent Polymers by Inverse Vulcanization.

Area of Science:

• Materials Science
• Polymer Chemistry
• Optical Engineering

Background:

• Developing infrared (IR) transparent polymers is crucial for IR optics, but balancing their optical and thermal properties is challenging due to inherent organic material absorption.
• Existing inorganic materials often have limitations in terms of processability and cost for IR optical devices.

Purpose of the Study:

• To develop novel IR transparent polymer materials with balanced thermal and optical properties.
• To introduce a new strategy for creating polymers suitable for IR optical applications, specifically focusing on IR lenses.

Main Methods:

• Inverse vulcanization was employed using a novel high boiling point symmetrical molecular norbornadiene derivative cross-linking agent (DMMD) and molten sulfur.
• Poly (S-r-DMMD) with varying sulfur content was synthesized by controlling the feed ratio of sulfur.
• The thermal properties (glass transition temperature, T_g) and IR transmittance (MWIR and LWIR) of the synthesized polymers were characterized.

Main Results:

• The prepared Poly (S-r-DMMD) exhibited tunable thermal properties with T_g ranging from 98.3 to 119.8 °C.
• High IR transmittance was achieved: 42.9-52.6% in the medium-wave IR (MWIR) and 1.5-5.29% in the long-wave IR (LWIR).
• Large-size, free-standing Fresnel lenses for IR imaging were successfully fabricated using hot-pressing, demonstrating the material's processability.

Conclusions:

• A novel strategy was established for balancing the thermal and optical properties of IR transparent polymer materials.
• The developed Poly (S-r-DMMD) offers a promising alternative to inorganic materials for IR optical devices.
• The material's suitability for fabricating IR Fresnel lenses highlights its potential for flexible design and production in IR optics.