Helix-Sense-Selective Encapsulation of Helical Poly(lactic acid)s within a Helical Cavity of Syndiotactic Poly(methyl methacrylate) with Helicity Memory
Helix-Sense-Selective Encapsulation of Helical Poly(lactic acid)s within a Helical Cavity of Syndiotactic Poly(methyl methacrylate) with Helicity Memory
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DOI：
10.1021/jacs.0c11204
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发表时间：
2020-12-30
影响因子：
15
通讯作者：
Yashima, Eiji
中科院分区：
文献类型：
--
作者：
Ikai, Tomoyuki;Kawabata, Satoshi;Yashima, Eiji
通过间规聚甲基丙烯酸甲酯(St-PMMA)螺旋腔内独特的“螺旋中”超结构的形成和单手螺旋度记忆，我们报道了一种具有高度对映体和螺旋选择性的螺旋状聚乳酸S(PLAs)的包埋。光学纯的L丙交酯和D-丙交酯分别开环活性聚合，然后用4-卤代苯甲酸酯和C-60单元封端，得到不同摩尔质量和窄摩尔质量分布的M-和P-螺旋聚乳酸，得到不含C-60和结合C-60的M-和P-聚乳酸。不含C-60和结合C-60的M-和P-PLA与非手性St-PMMA形成晶体包合物，同时在St-PMMA主链上形成择优螺旋诱导，从而形成相互同手的螺旋超结构。用去手性C-60取代后，诱导的螺旋状St-PMMA仍然保留，这表明St-PMMA的诱导螺旋性已被记忆。将C-60和C-60结合的螺旋聚乳酸选择性地包裹在光学活性的M-和P-St-PMMA的螺旋中空空间中，并用手性胺制备螺旋度存储器。M-和P-PLA优先被封装在M-和P-St-PMMA螺旋腔内，并且彼此具有相同的手性，而与终端单元无关。与不结合C-60的PLA相比，结合C-60的PLA在St-PMMA中具有更高的效率和对映体选择性。对映体选择性高度依赖于C-60结合的和不含C-60的聚乳酸的摩尔质量，并且随着聚乳酸摩尔质量的增加而显著增加。
We report a highly enantio- and helix-sense-selective encapsulation of helical poly(lactic acid)s (PLAs) through a unique "helix-in-helix" superstructure formation within the helical cavity of syndiotactic poly(methyl methacrylate) (st-PMMA) with a one-handed helicity memory, which enables the separation of the enantiomeric helices of the left (M)- and right (P)-handed-PLAs. The M- and P-helical PLAs with different molar masses and a narrow molar mass distribution were prepared by the ring-opening living polymerization of the optically pure L- and D-lactides, respectively, followed by end-capping of the terminal residues of the PLAs with a 4-halobenzoate and then a C-60 unit, giving the C-60-free and C-60-bound M- and P-PLAs. The C-60-free and C-60-bound M- and P-PLAs formed crystalline inclusion complexes with achiral st-PMMA accompanied by a preferred-handed helix induction in the st-PMMA backbone, thereby producing helix-in-helix superstructures with the same-handedness to each other. The induced helical st-PMMAs were retained after replacement with the achiral C-60, indicating the memory of the induced helicity of the st-PMMAs. Both the C-60-free and C-60-bound helical PLAs were enantio- and helix-sense selectively encapsulated into the helical hollow space of the optically active M- and P-st-PMMAs with the helicity memory prepared using chiral amines. The M- and P-PLAs are preferentially encapsulated within the M- and P-st-PMMA helical cavity with the same-handedness to each other, respectively, independent of the terminal units. The C-60-bound PLAs were more efficiently and enantioselectively trapped in the st-PMMA compared to the C-60-free PLAs. The enantioselectivities were highly dependent on the molar mass of the C-60-bound and C-60-free PLAs and significantly increased as the molar mass of the PLAs increased.