Entropy-Driven Depolymerization of Poly(dimethylsiloxane)
Entropy-Driven Depolymerization of Poly(dimethylsiloxane)
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聚二甲基硅氧烷的熵驱动解聚
DOI：
10.1021/acs.macromol.2c02554
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发表时间：
2023
期刊：
影响因子：
5.5
通讯作者：
Miller, Stephen A.
中科院分区：
文献类型：
--
作者：
Torgunrud, Jordan L.;Reverón Pérez, Aracelee M.;Spitzberg, Emily B.;Miller, Stephen A.
聚（二甲基硅氧烷）（PDMS）由于其独特的性能而被广泛使用，但需要从二氧化硅开始进行高污染和高能耗的合成。化学品回收提供了一个机会，再生具有可比性能的新材料，同时避免了新合成的低效率。在这里，我们报告的计算和实验结果解聚PDMS与二醇。计算上，用甲醇解聚总是吸能的，而用2-甲基-2，4-戊二醇（己二醇，HG）解聚在宽温度范围内是放能的。SiMe 2（OMe）2和己二醇之间的酸催化交换反应表明，由于熵有利的螯合作用，硅对二醇的热力学偏好。一个优化的程序解聚PDMS与己二醇的环状单体，M2 HG，开发和应用于各种商业PDMS源。环状硅氧烷是反应早期的副产物，需要两步工艺才能获得高纯度的M2 HG。即使在复杂的反应混合物中，该方法对PDMS也具有选择性，并且无论使用何种起始材料，都具有良好的产率（38-78%）。将M2 HG聚合回PDMS证明具有挑战性但可行。分别用三氟甲磺酸和对甲苯磺酸催化M2 HG开环聚合，得到低分子量的聚硅醇缩醛（Mn ~ 1500）和高分子量的聚二甲基硅氧烷（Mn ~ 39，900）。M2 HG与乙烯基醚和醛的三元共聚物也产生低分子量材料（Mn高达5000）。在阳离子乳液聚合条件下，成功地从M2 HG重构PDMS，提供高达Mn = 49，000的高分子量。
Poly(dimethylsiloxanes) (PDMSs) are widely used because of their unique properties but require a highly polluting and energy-intensive synthesis starting from silica. Chemical recycling offers an opportunity to regenerate new materials with comparable properties while avoiding the inefficiencies of thede novosynthesis. Herein, we report computational and experimental results of depolymerizing PDMS with diols. Computationally, depolymerization with methanol is always endergonic, while depolymerization with 2-methyl-2,4-pentanediol (hexylene glycol, HG) is exergonic over a wide temperature range. Acid-catalyzed exchange reactions between SiMe2(OMe)2and hexylene glycol show silicon’s thermodynamic preference for the diol due to entropically favorable chelation. An optimized procedure for depolymerizing PDMS with hexylene glycol to a cyclic monomer, M2HG, was developed and applied to a variety of commercial PDMS sources. Cyclic siloxanes are byproducts early in the reaction, requiring a two-step process to obtain highly pure M2HG. The procedure is selective for PDMS even in complex reaction mixtures and gives good yields (38–78%) regardless of the starting material used. Polymerizing M2HG back to PDMS proved challenging but feasible. Ring-opening polymerization of M2HG was catalyzed by trifluoromethanesulfonic acid orp-toluenesulfonic acid to yield low-molecular-weight polysilicon acetals (Mnup to 1500) or high-molecular-weight PDMS (Mn∼ 39,900), respectively. Terpolymerizations of M2HG with vinyl ethers and aldehydes also yielded low-molecular-weight material (Mnup to 5000). PDMS was successfully reconstituted from M2HG under cationic emulsion polymerization conditions, affording high molecular weights up toMn= 49,000.
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影响因子：
2.6
作者：
Torgunrud, Jordan L.;Faria, Alejandro J.;Miller, Stephen A.
通讯作者：
Miller, Stephen A.
DOI：
--
发表时间：
2015
期刊：
Resources and Technology
影响因子：
--
作者：
Maik Weidauer;Benedict Heyder;Daniel Woelki;Moritz Tschiersch;Angela Köhler;Stephan Enthaler
通讯作者：
Stephan Enthaler
填充弹性体的性能和负载之间的半经验关系
DOI：
--
发表时间：
1989
期刊：
影响因子：
--
作者：
A. Pouchelon;P. Vondracek
通讯作者：
P. Vondracek
影响因子：
5
作者：
Rupasinghe, Buddhima;Furgal, Joseph C.
通讯作者：
Furgal, Joseph C.
影响因子：
5.5
作者：
Ryosuke Hada;Arihiro Kanazawa;S. Aoshima
通讯作者：
Ryosuke Hada;Arihiro Kanazawa;S. Aoshima