Synthesis and characterization of siloxane‐based cyanate ester elastomers from readily available materials: a top‐down approach

Abstract

A number of siloxane‐based cyanate ester (SiCE) elastomers were prepared from commercially available starting reagents employing a hydrosilylation reaction. Each elastomer was designed to utilize 2,4,6‐tris(allyloxy)‐1,3,5‐triazine as a crosslinker and multifunctional vinyl component in the hydrosilylation reaction, ensuring that the triazine rings were completely formed, and thus the elastomers resemble fully cured cyanate ester networks. The hydride‐terminated siloxane components used were varied from small‐molecule siloxanes to pre‐polymers of different molecular weights. Attenuated total reflectance Fourier transform infrared analysis confirmed the successful hydrosilylation reaction and complete curing of the SiCE elastomers via functional group analysis. Thermal characterization by thermogravimetric analysis and differential scanning calorimetry demonstrated that thermal properties of the elastomers could be tailored depending on the type of siloxane component that was utilized. The gel content of the elastomers was also determined. Investigations into the effects of a platinum catalyst on the elastomers determined that the presence of the catalyst affected the thermochemical stability of the SiCE elastomers. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Synthesis, Characterization, and Thermal Properties of Fluoropyridyl-Functionalized Siloxanes of Diverse Polymeric Architectures

“…The pentyl ether functionalized network series net7a−7d demonstrated slight improvement in thermal stability with post-Soxhlet extraction compared with no extraction presumably due to the removal of the residual Pt catalyst that is known to cause accelerated thermal degradation with T d exceeding 378 °C to as high as 418 °C with increasing PDMS chain-length (n) inclusion. 9 A similar trend is observed of higher char yield with increasing PDMS chain length up to 43% for net7c that possesses higher silicon content, which oxidizes to SiC and SiO 2 char under inert polymer pyrolysis of the post-Soxhlet sample. Surprisingly, the T g remains relatively unaffected, ranging −42 to −49 °C by chain length for net7a and net7b, whereby longer chain length is expected to induce a plasticizing effect and increasing network chain mobility, thus lowering T g .…”

“…Selected thermal properties of networked 3,5-fluoropyridine functionalized silicone elastomers net7 and net8 using DSC and TGA are illustrated in Table . The pentyl ether functionalized network series net7a–7d demonstrated slight improvement in thermal stability with post-Soxhlet extraction compared with no extraction presumably due to the removal of the residual Pt catalyst that is known to cause accelerated thermal degradation with T d exceeding 378 °C to as high as 418 °C with increasing PDMS chain-length ( n ) inclusion . A similar trend is observed of higher char yield with increasing PDMS chain length up to 43% for net7c that possesses higher silicon content, which oxidizes to SiC and SiO 2 char under inert polymer pyrolysis of the post-Soxhlet sample.…”

“…Additionally, these materials can be accessed via facile procedures, including metal-free azide–alkyne and thiol-ene click chemistries. − However, one of the most common and rapid methods remains the platinum-catalyzed hydrosilylation reaction. The incorporation of siloxane segments into polymers provides a number of enhanced properties to these materials, such as low surface energy, chemical resistance, low T g , resistance to impact damage or fracture, and thermal stability. − Common siloxane additives include polydimethylsiloxane (PDMS) and polyhedral oligomeric silsequioxane (POSS) macromers, the latter receiving substantial recognition in recent years for its diverse features. The robust POSS cage architecture is an attractive platform due to its high degree of tunability and ease of incorporation, demonstrably augmenting their use in thermoplastic elastomers, polymer composites, and reprocessable thermosetting networks (vitrimers). − Hence, the incorporation of POSS components is a distinct and expedient option for the fabrication of novel high-performance thermosets and elastomers.…”

Organic–Inorganic Hybrid Thermal Insulation Materials Prepared via Hydrosilylation of Polysilsesquioxane Having Hydrosilyl Groups and Triallylisocyanurate

“…Characterization. 1 H, 13 C, and 29 Si nuclear magnetic resonance (NMR) measurements were performed on a Varian 500 MHz spectrometer. The samples were dissolved in deuterated chloroform (CDCl 3 ), and residual chloroform or tetramethylsilane was used as an internal standard for chemical shift referencing.…”

“…The samples were dissolved in deuterated chloroform (CDCl 3 ), and residual chloroform or tetramethylsilane was used as an internal standard for chemical shift referencing. 13 C and 29 Si solidstate NMR measurements were performed on a Varian 600 MHz spectrometer. Attenuated total reflection Fourier transform infrared (ATR−FTIR) spectra were recorded on a Shimadzu IR Affinity-1 spectrometer equipped with an ATR unit.…”