The full potential of sequence-defined macromolecules remains unexplored, hindered by the difficulty of synthesizing sufficient amounts for the investigation of the properties of such uniform structures and their derived materials. Herein, we report the bidirectional synthesis and thermal behavior analysis of sequence-defined oligourethanes. The synthesis was conducted on a large scale (up to 50 grams) using a straightforward protocol, yielding uniform macromolecules as validated by NMR, ESI-MS and SEC. With this approach, a library of uniform oligourethanes (up to the octamers) was produced using two structural units: a hydrogen-bonding carbamate and a methyl-substituted alternative structure. By varying the chain length, monomer sequence and functionality, we were able to perform a systematic study of the impact of hydrogen bonding on the thermal properties of polyurethanes. Thermal analysis of the discrete oligomers using DSC revealed that both the molecular weight and microstructure significantly affect the glass transition and melting temperatures. TGA measurements also revealed differences in the thermal stability of the oligomers, underscoring the significance of the primary structure of polyurethanes. Additionally, the influence of the terminal groups on the degradation pathway was assessed via pyrolysis-GC-MS, which specifically highlighted the increased thermal stability in the absence of hydroxyl end groups. This work shows the interest of using sequence-defined synthetic macromolecules for the elucidation of structure–property relationships and thereby facilitates their fine-tuning towards specific material applications.

中文翻译：

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均匀寡氨基甲酸酯的可扩展设计，用于链长、序列和端基对热性能的影响研究


序列定义的大分子的全部潜力仍未得到探索，由于难以合成足够的量来研究这种均匀结构及其衍生材料的性质。在此，我们报道了序列定义的寡氨基甲酸酯的双向合成和热行为分析。使用简单的方案进行大规模（高达 50 g）合成，产生均一的大分子，经 NMR、ESI-MS 和 SEC 验证。通过这种方法，使用两个结构单元（氢键氨基甲酸酯和甲基取代替代结构）产生了均匀的寡氨基甲酸酯库（直至八聚体）。通过改变链长、单体序列和功能，我们能够对氢键对聚氨酯热性能的影响进行系统研究。使用 DSC 对离散低聚物进行热分析表明，分子量和微观结构都会显著影响玻璃化转变和熔融温度。TGA 测量还揭示了低聚物热稳定性的差异，强调了聚氨酯一级结构的重要性。此外，通过热解-GC-MS 评估了末端基团对降解途径的影响，这特别强调了在没有羟基末端基团的情况下热稳定性增加。这项工作表明了使用序列定义的合成大分子来阐明结构-性质关系的兴趣，从而促进了它们对特定材料应用的微调。