High refractive index polythiourethane networks with high mechanical property via thiol-isocyanate click reaction

High refractive index polymers (HRIPs), especially sulfur-containing HRIPs, play an important role in optical materials; particularly the thermosetting sulfur-containing polyurethane is widely used in optical lenses. To understand the effect of thiol and isocyanate structures on thermosetting polythiourethane properties, a comprehensive study of the basic thermal, optical and mechanical properties of the obtained polythiourethane network structure was conducted, which results indicated that in addition to functionality and the presence of rigid groups affect the glass transition temperature, the conjugation effect and steric hindrance effect in the structure can also cause more changes in the glass transition temperature. All polythiourethane materials formed uniform and densely crosslinked network structures. Due to the introduction of highly polarizable sulfur atoms in 2,3-bis((2-mercaptoethyl)thio)-1-propanethiol (GST) and benzene rings in bis(isocyanatomethyl)benzene (XDI), the resulting polythiourethanes exhibited a high refractive index of 1.6559 (589 nm) and a tensile strength of 95.64 MPa while the Abbe's number was 33.24, fully meeting the lens requirements. The important structure-property relationships of polythiourethane will be helpful for the rational design of HRIPs.