Synthesis of polysaccharide-based block copolymers via olefin cross-metathesis
Synthesis of polysaccharide-based block copolymers via olefin cross-metathesis
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DOI：
10.1016/j.carbpol.2019.115530
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发表时间：
2020-02-01
影响因子：
11.2
通讯作者：
Edgar, Kevin J.
中科院分区：
文献类型：
--
作者：
Chen, Junyi;Kamitakahara, Hiroshi;Edgar, Kevin J.
许多研究人员已经制备了具有刷状接枝结构的多糖基共聚物。相比之下，制备线性多糖基嵌段共聚物是一项具有挑战性的工作。尽管以可再生为基础的线性嵌段共聚物具有明显的应用潜力，但仅有几种方法被报道用于制备此类结构。区域选择性多糖端基功能化的挑战性阻碍了它们的制备。在这里，我们报告了一种不同的、灵活的线性嵌段共聚物的方法，展示了可再生的天然纤维素的衍生品。为了说明这一方法，采用偶联策略合成了三甲基纤维素-b-聚乙二醇、三甲基纤维素-b-聚四氢呋喃和三甲基纤维素-b-聚乳酸。通过将三甲基纤维素与不饱和醇溶解制得不饱和烷基缩醛，三甲基纤维素在还原端的异构碳被特定区域功能化。随后，采用温和而通用的烯烃交叉复分解反应，将三甲基纤维素嵌段与包括丙烯酸酯聚合物嵌段在内的一系列丙烯酸酯衍生物高效偶联(100%转化率)。核磁共振波谱确证了目标嵌段共聚结构，尺寸排阻色谱(SEC)表明在偶联过程中聚合度保持较好。结果表明，这种新的溶剂分解/交叉复分解方法是一种很有前途的方法，可以用于制备基于多糖基的线型AB嵌段共聚物，也可能是ABC嵌段共聚物。
Polysaccharide-based copolymers with brush-like, graft architectures have been prepared by many investigators. In contrast, it is challenging to prepare linear polysaccharide-based block copolymers. Only a few approaches have been reported for preparation of such architectures, despite the clear application potential of renewable-based, linear block copolymers. The challenging nature of regioselective polysaccharide end-group functionalization has impeded their preparation. Herein we report a different, flexible approach to linear block copolymers, demonstrated for derivatives of renewable, natural cellulose. To illustrate this approach, trimethyl cellulose-b-poly(ethylene glycol), trimethyl cellulose-b-poly(tetrahydrofuran) and trimethyl cellulose-b-poly(lactic acid) were synthesized by a coupling strategy. Trimethyl cellulose was functionalized regiospecifically at the reducing end anomeric carbon to create an.-unsaturated alkyl acetal by solvolysis of trimethyl cellulose with an.-unsaturated alcohol. Subsequently, mild and versatile olefin cross-metathesis was used to couple efficiently (100% conversion) the trimethyl cellulose block with a series of acrylate derivatives, including acrylated polymer blocks. The targeted block co-polymeric structures were confirmed by nuclear magnetic resonance (NMR) spectroscopy, and the degree of polymerization was relatively well-preserved during the coupling step, as shown by size exclusion chromatography (SEC). The results confirm that this new solvolysis/cross-metathesis method is a promising approach to polysaccharide-based linear AB, and likely ABC, block copolymers.