有机硅凝胶的可调、无催化剂制备,Industrial & Engineering Chemistry Research

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有机硅凝胶的可调、无催化剂制备
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2021-10-13 , DOI: 10.1021/acs.iecr.1c02369
Guanhua Lu ₁ , Alyssa F. Schneider ₁ , Melanie Vanderpol ₁ , Emily K. Lu ₁ , Michael Y. Wong ₁ , Michael A. Brook ₁

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有机硅凝胶通常由用硅油溶胀的有机硅弹性体组成；用于固化的催化剂和/或其副产品保留在最终材料中。由这些催化剂残留物引起的并发症，包括对热行为的影响、由于持续的催化剂反应性导致的机械性能缓慢变化、由于浸出导致的毒性等，都可能影响凝胶应用。我们之前报道了一种用于弹性体的无催化剂、高温、自动氧化固化方法，其中交联是通过自由基介导的氢从氢硅烷 (SiH) 起始材料中的氧夺取而引发的；传播通过自由基链进行。我们现在报告该方法特别适用于硅凝胶合成，并描述了具有各种机械性能和凝胶分数的硅凝胶库的制备。使用自氧化固化方法制备的有机硅凝胶的杨氏模量很容易通过起始材料中的 SiH 浓度以及固化时间和温度进行调整，如 220 至 300 °C 所示。线性有机硅的起始材料比例——氢化物官能化聚二甲基硅氧烷 (PDMS) 加上可选的非官能化 PDMS 油——变化以控制起始材料中的 SiH 浓度，其范围为 0.3 至 7.2 mol%。所有材料均在 220 °C 下在一周内完全固化，含有 <30% 的可萃取材料，杨氏模量从 0.78 到 2.75 MPa。产生更软的凝胶（>0. 02 MPa），通过在完全固化之前将配方从热源中取出，可提取材料的含量更高（提取后质量损失高达 92%）。更高的固化温度允许在更短的反应时间内实现类似的凝胶结构，在 300 °C 下只需 2.8 小时，但会导致材料变脆。然而，当在氧气气氛中进行氧化时，凝胶可以在 250°C 下可靠地合成 1.5 小时。

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Tunable, Catalyst-Free Preparation of Silicone Gels

Silicone gels are typically comprised of silicone elastomers swollen with silicone oil; catalysts used for cure and/or their byproducts remain in the final material. Complications arising from these catalyst residues, including effects on thermal behavior, slow changes in mechanical properties due to continued catalyst reactivity, toxicity due to leaching, etc., can all work to compromise gel applications. We previously reported a catalyst-free, high-temperature, autoxidation cure method for elastomers whereby crosslinking is initiated through radical-mediated hydrogen abstraction by oxygen from a hydrosilane (SiH) starting material; propagation proceeds through a radical chain. We now report that this method is particularly amenable to silicone gel synthesis and describe the preparation of a library of silicone gels with various mechanical properties and gel fractions. Young’s modulus of silicone gels prepared using the autoxidation cure method is readily tuned by the SiH concentration in the starting materials and the time and temperature of cure, as shown from 220 to 300 °C. Starting material ratios of linear silicones—hydride-functional polydimethylsiloxane (PDMS) plus, optionally, nonfunctional PDMS oil—were varied to control the SiH concentration in the starting materials, which ranged from 0.3 to 7.2 mol %. All materials were fully cured in a week at 220 °C, contained <30% extractable materials, and exhibited Young’s moduli from 0.78 to 2.75 MPa. Softer gels were produced (>0.02 MPa) with higher levels of the extractable material (up to 92% mass loss following extraction) by removing the formulations from heat prior to full cure. Higher cure temperatures allowed analogous gel structures to be realized in shorter reaction times, in as little as 2.8 h at 300 °C, but resulted in brittle materials. However, gels can be reliably synthesized for as little as 1.5 h at 250 °C when the oxidation is performed in an oxygen atmosphere.

更新日期：2021-10-27

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