Takizawa Kenichi, Tang Chuanbing, Hawker Craig J
Materials Research Laboratory and Department of Materials, University of California, Santa Barbara, California 93106, USA.
J Am Chem Soc. 2008 Feb 6;130(5):1718-26. doi: 10.1021/ja077149w. Epub 2008 Jan 12.
The synthesis of molecularly defined epsilon-caprolactone oligomers and polymers up to the 64-mer, via an exponential growth strategy, is described. By careful selection of orthogonal protecting groups, t-butyldimethylsilyl (TBDMS) ether for the hydroxyl group and benzyl (Bn) ester for the carboxylic acid group, a highly efficient synthetic strategy was developed with yields for both deprotection steps being essentially quantitative and for the coupling reactions using 1,3-dicyclohexylcarbodiimide (DCC), yields of 80-95% were obtained even at high molecular weights. This allows monodisperse dimers, tetramers, octamers, 16-mers, 32-mers and 64-mers to be prepared in gram quantities and fully characterized using mass spectroscopy, size exclusion chromatography (SEC), and IR and NMR spectroscopy. Thermal and physical properties were measured using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). These results conclusively show a distinct structure/property relationship with a close correlation between the number of repeat units and physical properties. In addition, a number of marked differences were observed on comparison with the parent poly(caprolactone) polymer.
本文描述了通过指数增长策略合成分子定义明确的ε-己内酯低聚物和聚合物（直至64聚体）的方法。通过精心选择正交保护基团，羟基用叔丁基二甲基硅烷基（TBDMS）醚保护，羧酸基团用苄基（Bn）酯保护，开发了一种高效的合成策略，两个脱保护步骤的产率基本为定量，对于使用1,3 - 二环己基碳二亚胺（DCC）的偶联反应，即使在高分子量下产率也能达到80 - 95%。这使得能够以克级量制备单分散二聚体、四聚体、八聚体、16聚体、32聚体和64聚体，并使用质谱、尺寸排阻色谱（SEC）、红外光谱和核磁共振光谱进行全面表征。使用热重分析（TGA）、差示扫描量热法（DSC）、原子力显微镜（AFM）和小角X射线散射（SAXS）测量热性能和物理性能。这些结果确凿地表明了一种独特的结构/性能关系，即重复单元数量与物理性能之间存在密切相关性。此外，与母体聚己内酯聚合物相比，观察到了许多显著差异。
