Facile thiol-ene reactions of vinyl T₁₀/T₁₂ silsesquioxanes for controlled refractive indices for transparent fiber glass reinforced composites

Abstract

A series of thioether-functionalized silsesquioxanes (SQs) was synthesized by radically initiated thiol-ene reactions of vinyl T 10 / T 12 SQ cages with a variety of commercially available thiols. The objectives of this study were to develop model reactions as the basis for using the vinyl T 10/12 compounds as novel crosslinking agents in the synthesis of new types of thiol-ene crosslinked polymers. A second motivation was to develop model compounds with controlled refractive indices and Abbe numbers as possibly modifiers of polymers used for a wide variety of optical and photonic applications. The reactions proceed under mild conditions over 24 h to give thioether SQs in high yields (>90%) and high purity without complex workup. The ease of synthesis coupled with the wide variety and availability of functionalized thiols provides a simple route to elaborating and functionalizing vinyl SQ cages. In addition, the resulting compounds exhibit refractive indices to 1.52 coupled with Abbe numbers to 51 due to the uniquely high electron density provided by the incorporated sulfur atoms, making them ideal compounds for use with optically transparent materials. In addition, cured forms of these compounds provide methods of raising the Abbe number of epoxy resins designed to index match fiberglass with the intent of making transparent fiberglass reinforced composites.

Refractive index evolution of various commercial acrylic resins during photopolymerization

“…If the refractive index of (meth)acrylic resins is often known, its evolution during their polymerization is never specified in the technical datasheets. However, these data are essential for applications in need of well controlled optical properties (holographic data-storage (HDS) technologies [15], transparent glass cloth reinforced plastics [16], gradient-index (GRIN) optics [17], transparent fiber glass reinforced composites [18] etc), as well as for the elaboration of thick homogeneous composite materials, where the prediction of the cure light transmission evolution and its influence on conversion profiles and cure depth is fundamental [19]. This work aims to characterize the refractive index evolution of some usual and commercial photocurable (meth)acrylic resins.…”

Heat resistant and transparent organic–inorganic hybrid materials composed of N‐allylmaleimide copolymer and random‐type SH‐modified silsesquioxane

“…The random‐type SQ is mostly a liquid compound and it is appropriate for the design of high‐performance transparent polymer nanohybrid materials. Several articles have been reported for the synthesis and characterization of organic–inorganic polymer hybrids using various SQs, including thermal property, fluorescence, phase‐separation structure, and nanocomposites of POSS‐maleimide polymer hybrids.…”