No abstract

Derivatization of the porphyrin TPMP improves its dispersion in silicone dielectric elastomers, resulting in materials capable of achieving high actuations at low voltages.

Soybean oil-derived polyurethanes, while much greener than those derived from isocyanates, have a problematic combustion profile; concerns exist about the nitrogen-containing compounds found in the smoke. Silicones typically burn cleanly to form an insulating silica layer upon combustion. We have examined the ability of silicones to convey improved thermal stability to soybean oil. The oil was modified via an ene reaction to incorporate an alkoxysilane functionality that was used in a subsequent Piers–Rubinsztajn reaction with silicones to create foams and elastomers. Cross-linked materials with densities ranging from ∼0.6 to 0.9 g/mL and containing up 76% by weight soybean oil were prepared. The addition of varying amounts of a linear PDMS chain extender allowed for control of the modulus (0.04–0.32 MPa). Cross-linking rapidly occurred, <60 s for full cure. Foams were produced without the need for external blowing agents, due to the generation of methane as a byproduct of the Piers–Rubinsztajn reaction. The soybean oil/silicone materials burned cleanly and without dripping, as shown in particular with the elastomer containing 76 wt % soybean oil. The external surfaces of the objects, after combustion, were rigid silica-rich structures.

Antioxidants are important mediators of radical processes. Nature exploits a variety of antioxidants, including vitamins, to moderate oxidation in living systems. Silicone oils and elastomers, widely used in personal care...

The encapsulation of hemin in polymer systems represents a powerful tool for the preparation of synthetic enzymes. Reported systems largely focus on the creation of hydrogels or microreactors that require a degree of modification to the hemin molecule itself. The straightforward synthesis of hydrophobic hemin‐aminosilicone crosslinked silicone elastomers is described with peroxidase like reactivity. Elastomers are formed from purely ionic interactions between commercial aminoalkylsilicones and native hemin, which acts as a crosslinker. Elastomers prepared from ethylene diamine‐based silicones are robust elastomers in which hemin is retained, while hemin can leach monoamine analogues into the adjacent aqueous environment. The system is easily tunable, allowing for precise control of the hemin concentration and the physical properties of the elastomer. Upon exposure to peroxide‐containing solutions, elastomers readily oxidize the substrate 3′,3′,5′,5′‐tetramethylbenzidine at the interface. Elastomers containing excess amine show greater catalytic efficiency due to the coordination of the amines to the iron center of hemin, which is known to be activating. The reaction can be followed using UV‐visible spectroscopy; rates of reaction and Michaelis–Menten parameters are derived.