Tannic Acid as a Natural Crosslinker for Catalyst-Free Silicone Elastomers From Hydrogen Bonding to Covalent Bonding

Abstract

The construction of silicone elastomers crosslinked by a natural crosslinker under a catalyst-free method is highly desirable. Herein we present catalyst-free silicone elastomers (SEs) by simply introducing tannic acid (TA) as a natural crosslinker when using poly (aminopropylmethylsiloxane-co-dimethylsiloxane) (PAPMS) as the base polymer. The crosslinked bonding of these SEs can be easily changed from hydrogen bonding to covalent bonding by altering the curing reaction from room temperature to heating condition. The formability and mechanical properties of the SEs can be tuned by altering various factors, including processing technique, the amount of TA and aminopropyl-terminated polydimethylsiloxane, the molecular weight and -NH2 content of PAPMS, and the amount of reinforcing filler. The hydrogen bonding was proved by the reversible crosslinking of the elastomers, which can be gradually dissolved in tetrahydrofuran and re-formed after removing the solvent. The covalent bonding was proved by a model reaction of catechol and n-decylamine and occurred through a combination of hydroxylamine reaction and Michael addition reaction. These elastomers exhibit good thermal stability and excellent hydrophobic property and can bond iron sheets to hold the weight of 500 g, indicating their promising as adhesives. These results reveal that TA as a natural product is a suitable “green” crosslinker for the construction of catalyst-free silicone elastomers by a simple crosslinking strategy. Under this strategy, TA and more natural polyphenols could be certainly utilized as crosslinkers to fabricate more organic elastomers by selecting amine-containing polymers and further explore their extensive applications in adhesives, sealants, insulators, sensors, and so forth.

Noncovalent functionalization of boron nitride via chelation of tannic acid with Fe ions for constructing high thermally conductive polymeric composites

“…Moreover, the TA exhibited good interfacial affinity with Fe 3+ , which was conducive to the formation of a stable TA/Fe chelate complexes. The pH‐dependent transition between TA and Fe 3+ binding to the dominant TA/Fe structure is shown in Figure 1B 34–36 . Meanwhile, plenty of hydrophilic units (phenol groups) promoted the dispersion of TA/Fe‐BN particles in the NR latex.…”

“…The pHdependent transition between TA and Fe 3+ binding to the dominant TA/Fe structure is shown in Figure 1B. [34][35][36] Meanwhile, plenty of hydrophilic units (phenol groups) promoted the dispersion of TA/Fe-BN particles in the NR latex. the BN surface.…”

Dispersion Enhancement of Boron Nitride Nanotubes in a Wide Range of Solvents Using Plant Polyphenol-Based Surface Modification

“…43 For the hydrophobic modification of BNNT-TA, aminecontaining alkyl chain molecules, for example, decylamine (DA), were used. 44 Fast agglomeration was observed following the addition of DA to the TA aqueous dispersion of BNNT. The fast agglomeration may be attributed to the increased hydrophobicity of BNNT-TA due to the attachment of DA (Figure 1a; right).…”

“…For the hydrophobic modification of BNNT-TA, amine-containing alkyl chain molecules, for example, decylamine (DA), were used . Fast agglomeration was observed following the addition of DA to the TA aqueous dispersion of BNNT.…”

Antioxidant Silicone Elastomers without Covalent Cross-Links

“…19 Kong et al demonstrated that aminosilicones would combine with tannic acid (Figure 1) using hydrogen bonding in a simple manner to achieve silicone elastomers linked via hydrogen bonds. 20 We wished to understand if phenolic hydrogen donors 21 � functional groups that are also antioxidants�could be used to make (re)processable silicone elastomers. Such materials would be more sustainable both because of facile reprocessing and the incorporation of natural materials.…”