Effect of cross-link density on optoelectronic properties of thermally cured 1,2-epoxy-5-hexene incorporated polysiloxane

The synergesic effect from copolymerising polysiloxane and epoxy functionality offer a viable encapsulant material for use in electronic devices. A series of epoxy group-containing organopolysiloxane without ether bond spacer was prepared. The cross-link density was progressively monitored by controlling the mole ratio of the epoxy monomer. Thermal, optical, dielectric and hardness properties were measured and related to the cross-link density. The crosslink density affect an increase in refractive indices in the range 1.4359–1.4655 and dielectric constants in the range 2.78–3.34 at 500 MHz. Transparency were in the range 60–80% in visible region. A higher crosslink structure displays an improved transparency in the UV–visible region. These observations were related to changes in free volume and group polarizability and discussed within the scope of Lorentz–Lorenz relationship.

► Organopolysiloxane containing epoxy groups were studied.
► Optoelectronic properties were quantified based on the Lorentz-Lorenz model.
► They were related well with the cross-link density.