Aryl‐group substituted polysiloxanes with high‐optical transmission, thermal stability, and refractive index

Oligo-Condensation Reactions of Silanediols with Conservation of Solid-State-Structural Features

Oligo- and polysiloxanes are usually prepared by condensation reactions in solvents without control of stereochemistry. Here we present a solventless thermal condensation of stable organosilanols. We investigated the condensation reactions of organosilanediols with different organic substituents, having in common at least one aromatic group. The condensation kinetics of the precursors observed by NMR spectroscopy revealed a strong dependence on temperature, time, and substitution pattern at the silicon atom. SEC measurements showed that chain length increases with increasing condensation temperature and time and lower steric demand of the substituents, which also influences the glass transition temperatures (Tg) of the resulting oligo- or polymers. X-ray diffraction studies of the crystalline silanediols and their condensation products revealed a structural correlation between the substituent location in the crystalline precursors and the formed macromolecules induced by the hydrogen bonding pattern. In certain cases, it is possible to carry out topotactic polymerization in the solid-state, which has its origin in the crystal structure.

H-bond interaction traps vibrating fluorophore in polyurethane matrix for bifunctional environmental monitoring

A simple strategy is presented for the bifunctional detection of environmental organic vapor and temperature by utilizing H-bond interactions to trap a butterfly-vibration-based fluorophore (DPAC-OH) in a polyurethane (PU) matrix. The method opens up a new path for large-scale environmental inspections and the design of dual-response luminescent materials.

Cobalt-Catalyzed Regiodivergent Double Hydrosilylation of Arylacetylenes

Double hydrosilylation of alkynes represents a straightforward method to synthesize bis(silane)s, yet it is challenging if α-substituted vinylsilanes act as the intermediates. Here, a cobalt-catalyzed regiodivergent double hydrosilylation of arylacetylenes is reported for the first time involving this challenge, accessing both vicinal and geminal bis(silane)s with exclusive regioselectivity. Various novel bis(silane)s containing Si-H bonds can be easily obtained. The gram-scale reactions could be performed smoothly. Preliminarily mechanistic studies demonstrated that the reactions were initiated by cobalt-catalyzed α-hydrosilylation of alkynes, followed by cobalt-catalyzed β-hydrosilylation of the α-vinylsilanes to deliver vicinal bis(silane)s, or hydride-catalyzed α-hydrosilylation to give geminal ones. Notably, these bis(silane)s can be used for the synthesis of high-refractive-index polymers (n_d up to 1.83), demonstrating great potential utility in optical materials.

High Refractive Index, Enantiopure Silicones Based on BINOL

The high refractive index aromatic compound, binaphthol (BINOL), is readily incorporated into silicone polymer chains using the Piers-Rubinsztajn reaction; alternating and random linear copolymers, and elastomers are available. The highest refractive index (RI) materials were BINOL rich. It was not possible to directly make high refractive index linear polymers with very short HSi-capped, telechelic silicone chains, as they did not react cleanly. However, chain extending short vinyl-capped BINOL macromers with simple arylsilanes using hydrosilylation led to polymers with molar mass up to 8000 and refractive indices up to 1.58. Elastomers were prepared using similar processes. The reactions are facile to practice and suggest BINOL could be harnessed in these and other processes to augment RI. This article is protected by copyright. All rights reserved.