Self-crosslinkable poly(urethane urea)-reinforced silica aerogels

Abstract

Mechanically reinforced organic-inorganic hybrid silica aerogels are produced from simultaneous hydrolysis and condensation reactions of silane precursorstetraethoxy silane (TEOS) and aminopropyltriethoxysilane (APTES)and silane-modified polyurethane urea molecules each carrying multiple ($3) reactive silane groups. In this manner, the post-gelation crosslinking reactions are avoided, the amount of polymer introduced into the aerogel structures is controlled, and the chain length between two crosslink points is tailored. The long chain polymer molecules introduce a certain degree of flexibility to the hybrid aerogel structures. The morphology, compressive properties, and surface area are obtained respectively using scanning electron microscopy, Instron tensile testers, and Brunauer-Emmett-Teller (BET) surface area analysis. The data on solid state 13 C and 29 Si NMR spectra reveal chemical reactions of the silane-modified polymers with the silica particle networks. Small angle X-ray scattering (SAXS) data are used to determine the fractal dimension of the silica networks. It is found that the self-crosslinkable multifunctional polyurethane urea chains form coatings on the silica networks and produce large enhancements in compressive modulus although with increases in shrinkage and bulk density.

Magnetic nanocomposites based on shape memory polyurethanes

“…to -3, implying rough particle surfaces [28]. The fractal dimension is lower for the most concentrates samples, indicating a rather smooth surface, which could be related with low amount of polymeric matrix adhered on their surfaces due to the reduced compatibility between nanoparticles and polymeric matrix, as was envisaged in our previous work [4].…”

Robust and superhydrophobic thiourethane bridged polysilsesquioxane aerogels as potential thermal insulation materials

“…In order to widen its applications as a functional material, the silica aerogel with high flexibility, good compression elasticity and applicable mechanical strength is the target for material scientists. 37,38 In this work, all thiourethane bridged polysilsesqiuoxane aerogel exhibit excellent mechanical properties and can withstand at least 50% deformation under compressions (Table 1 and Fig. 3).…”

Siloxane-inorganic chemical crosslinking of hyaluronic acid – based hybrid hydrogels: Structural characterization

“…Although T 2 signal has low intensity in 29 Si MAS NMR spectra, it implies different grafting degrees for different hybrid-organosilanes hydrogels composition (Peixoto et al, 2016). The relative absence of chemical shifts between -46 and -50 ppm could be attributed to T 1 prompts that APTES has reacted forming the siloxane structure in the aerogels and xerogels (Duan et al, 2015).…”