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Polymers

C&EN 中文版

立体化学控制打造出高强度粘性聚合物

用手性阴离子催化剂制备聚乙烯基醚，将其从小众材料转化为实用性塑料

by Bethany Halford
April 2, 2019
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从制药行业常用的化学中获得灵感，化学家们在制造聚乙烯基醚时使用了手性阴离子来控制立体化学。北卡罗来纳大学教堂山分校的化学家Frank A. Leibfarth谈到这项研究时说，由此产生的高强度粘合性聚合物可用于制造轻质复合材料，用于自行车、船只和汽车等应用。他是在美国化学学会在奥兰多举行的全国会议上一个高分子化学讨论专题上发言的。

Leibfarth说，在此之前，聚乙烯基醚一直是相当小众的产品，因为它们无规—即从聚合物主链上脱离的醚侧链的立体化学是随机的。所得聚合物在室温下为粘性液体，主要用作粘合剂。

A photo of viscous liquid drops and fluffy white plastic pieces.
当聚异丁基乙烯基醚中侧链的立体化学呈无规状态，聚合物是粘性液体（左）。当91％的侧链具有相同的立体化学时，该聚合物是固体（右）。

Leibfarth和博士后Aaron J. Teator认为，可以通过控制醚侧链的立体化学来改善聚乙烯基醚的性质，使它们全部相同，或者如聚合物化学家所述，是全同立构的。Leibfarth说，他受到了诺贝尔奖获奖化学家Karl Ziegler和Giulio Natta的启发，后两者开发了一种生产全同立构聚烯烃（如聚丙烯）的催化剂。

“这个从无规聚丙烯到全同立构聚丙烯的转变，创造了数十亿美元的产业，因为无规聚丙烯几乎没用，”Leibfarth说。但Ziegler-Natta催化剂在路易斯碱性杂原子如氧的存在下会中毒，这意味着它们不能用于制造富氧的聚乙烯基醚。

为了在制备聚乙烯基醚时控制立体化学，Leibfarth和Teator采用了手性阴离子催化，该技术自2000年以来就被用于控制小分子的立体化学。阳离子聚合在具有低介电常数的溶剂中进行，因此在生长的聚合物链末端的阳离子与手性阴离子紧密配对，该手性阴离子决定下一个单体将添加到链的哪一侧，因此得到全同立构聚合物（如图）。

A chiral anion blocks one side of the growing polymer chain in a cationic polymerization of poly(vinyl ether).
随着聚乙烯基醚链的生长，手性阴离子阻挡住一侧，决定了单体添加的立体化学。

Leibfarth说，全同立构聚乙烯基醚具有优异的性能。它与商业化聚烯烃类似，但对玻璃等极性基材的粘附性更好。Leibfarth和Teator还于3月底在《科学》杂志上发表了该研究（DOI: 10.1126/science.aaw1703），并为该工艺提交了临时专利申请（62/719,240）。

康奈尔大学的高分子化学家Geoffrey W. Coates称这项研究是“结合了机械、合成、立体化学和聚合物属性的杰作。“他补充说，自70年前化学家Calvin Schildknecht最初提出立体控制阳离子聚合以来，相关研究较少，而现在出现了这样一个令人兴奋的进步，这将重振这一聚合物化学重要领域的研究。

本文由Nina Sun为C&EN译为中文。英文原文在此。

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2024 American Chemical Society

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