Antioxidant Silicone Elastomers without Covalent Cross-Links

Abstract

Improved sustainability is associated with elastomers that readily breakdown in the environment at end of life and, as importantly, that can be reprocessed/reused long before end of life arises. We report the preparation of silicone elastomers that possess both thermoplasticityreprocessabilityand antioxidant activity. A combination of ionic and H-bonding links natural phenolic antioxidants, including catechol, pyrogallol, tannic acid, and others, to telechelic aminoalkylsilicones. The mechanical properties of the elastomers, including their processability, are intimately linked to the ratio of [ArOH]/[H2NR] that was found to be optimal when the ratio exceeded 1:1.

Functional silicone oils and elastomers: new routes lead to new properties

“…9C); in some cases, the latter bonding motifs are sufficient to crosslink silicones. 70 7.1.1.3 Aminals. When the extremely reactive (and toxic) aldehyde formaldehyde was reacted with aminosilicones, it was shown not to stop at the imine stage but reacted further to give aminal crosslinks.…”

“…9C). 69,70 Very resilient bonding can result from the combination of any bonds of lower energies/bond, including aromatic association (that can include p-p bonding, Fig. 7D), ionic bonds and H-bonding -e.g., DNA.…”

“…The pK a of ammonium salts and phenols is very similar. As a consequence, it is possible to create elastomers by using a combination of H-and ionic bonding; 70,87,88 both small molecules like catechol and large molecules like tannic acid participate as crosslinkers with telechelic aminosilicones. The product elastomers are excellent antioxidants.…”

Biodegradable, crosslinked silicone-gelatin hydrogels

“…Several strategies have been developed to facilitate the reuse of silicones, e.g. , dynamic bonds 8 and non-covalently crosslinked systems, 9,10 among others. Note that these processes allow the formation of elastomers while avoiding the need for metal catalysts.…”

Thermoplastic, redox recyclable silicone–lipoamide elastomers

“…8,9 There is a subclass of thermoplastic materials made using these bonding strategies in which the agents responsible for thermoplasticity are biological in origin, including coumarin, 10 vanillin, 11 sugars, 12 beta alanine, 13 thiosuccinic acid, 14 and tannic acid. 15 While not yet demonstrated, it can be expected that natural processes will have an easier time degrading the biological crosslinks leaving silicone oil behind; silicone oil have been shown to exhibit surprisingly facile degradation in the environment (over a few years). [16][17][18] α-Lipoic acid 1 (LPA) is an anti-oxidant found in humans 19 and animals.…”