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Autoxidation: Catalyst-Free Route to Silicone Rubbers by Crosslinking Si-H Functional Groups


Most traditional methods for silicone elastomer preparation involve catalysts whose incomplete removal can result in compromised thermal stability of the product elastomers and/or safety concerns. Herein, we report the oxidative curing of hydrosilane (H-Si) functionalized polymers to generate silicone elastomers at 250 oC in air but in the absence of catalysts. Both oxygen and Si-H groups are required for the oxidative curing process to occur; standard Me3Si-terminated silicone polymers exhibited no change under the same conditions. There are essentially no restrictions on molecular weights and the nature of Si-H (terminal or pendant) groups exploited in the precursor HSi-containing polymers. The product elastomers are bubble-free, transparent and colorless; they do not exhibit any yellowing at after thermal aging at 300 oC in air for 7 days. The moduli can be easily tuned by curing time and [HSi] in the precursors. Chain extension arises from conversion of SiH groups to Si-O-Si linkages, and crosslinks and chain extension are produced via radically induced ether formation (first step: RR’R”SiH + O2 + MeSi-silicone → RR’R”SiO-CH2Si-silicone + oxygen species). The efficiency of the radical chain and the resulting crosslinking processes increase with temperature. This process provides a facile, economic, green and catalyst free way to manufacture silicone elastomers from inexpensive, readily available starting materials.

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Publication details

The article was received on 27 Aug 2019, accepted on 08 Nov 2019 and first published on 08 Nov 2019

Article type: Paper
DOI: 10.1039/C9GC03026C
Green Chem., 2019, Accepted Manuscript

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    Autoxidation: Catalyst-Free Route to Silicone Rubbers by Crosslinking Si-H Functional Groups

    M. Y. Wong, A. Schneider, G. Lu, Y. Chen and M. A. Brook, Green Chem., 2019, Accepted Manuscript , DOI: 10.1039/C9GC03026C

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