An H-polymer has an architecture that consists of four branches symmetrically attached to the ends of a polymer backbone, similar in shape to the letter “H”. Here, a renewable H-polymer efficiently synthesized using only ring-opening transesterification is demonstrated. The strategy relies on a tetrafunctional poly(±-lactide) macroinitiator, from which four poly(±-lactide) branches are grown simultaneously. ¹H NMR spectroscopy, size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization (MALDI) spectrometry were used to verify the macroinitiator purity. Branch growth was probed using ¹H NMR spectroscopy and SEC to reveal unique transesterification phenomena that can be controlled to yield architecturally pure or more complex materials. H-shaped PLA was prepared at the multigram scale with a weight-average molar mass M_w > 100 kg/mol and low dispersity Đ < 1.15. Purification involved routine precipitations steps, which yielded products that were architecturally relatively pure (∼93%). Small-amplitude oscillatory shear and extensional rheology measurements demonstrate the unique viscoelastic behavior associated with the H-shaped architecture.

中文翻译：

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H型聚丙交酯的制备及表征


H-聚合物的结构由四个分支组成，对称地连接到聚合物主链的末端，形状类似于字母“H”。在这里，展示了仅使用开环酯交换反应有效合成的可再生 H 聚合物。该策略依赖于四官能聚(±-丙交酯)大分子引发剂，四个聚(±-丙交酯)分支同时生长。 ¹ H NMR 光谱、尺寸排阻色谱 (SEC) 和基质辅助激光解吸/电离 (MALDI) 光谱用于验证大分子引发剂的纯度。使用 ¹ H NMR 光谱和SEC 探测支链生长，以揭示独特的酯交换现象，可以控制该现象以产生结构纯或更复杂的材料。在多克规模下制备了重均摩尔质量 M _w > 100 kg/mol 和低分散度 Đ < 1.15 的 H 形 PLA。纯化涉及常规沉淀步骤，产生的产物在结构上相对纯净（~93%）。小振幅振荡剪切和拉伸流变学测量证明了与 H 形结构相关的独特粘弹性行为。