Molecularly Defined Caprolactone Oligomers and Polymers: Synthesis and Characterization
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- 作者：Kenichi Takizawa ; Chuanbing Tang ; Craig J. Hawker
- 刊名：Journal of the American Chemical Society
- 出版年：2008
- 出版时间：February 6, 2008
- 年：2008
- 卷：130
- 期：5
- 页码：1718 - 1726
- 全文大小：947K
- 年卷期：v.130,no.5(February 6, 2008)
- ISSN：1520-5126
文摘
The synthesis of molecularly defined 
-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 acidgroup, a highly efficient synthetic strategy was developed with yields for both deprotection steps beingessentially quantitative and for the coupling reactions using 1,3-dicyclohexylcarbodiimide (DCC), yields of80-95% 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 usingmass spectroscopy, size exclusion chromatography (SEC), and IR and NMR spectroscopy. Thermal andphysical properties were measured using thermogravimetric analysis (TGA), differential scanning calorimetry(DSC), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). These results conclusivelyshow a distinct structure/property relationship with a close correlation between the number of repeat unitsand physical properties. In addition, a number of marked differences were observed on comparison withthe parent poly(caprolactone) polymer.
-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 acidgroup, a highly efficient synthetic strategy was developed with yields for both deprotection steps beingessentially quantitative and for the coupling reactions using 1,3-dicyclohexylcarbodiimide (DCC), yields of80-95% 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 usingmass spectroscopy, size exclusion chromatography (SEC), and IR and NMR spectroscopy. Thermal andphysical properties were measured using thermogravimetric analysis (TGA), differential scanning calorimetry(DSC), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS). These results conclusivelyshow a distinct structure/property relationship with a close correlation between the number of repeat unitsand physical properties. In addition, a number of marked differences were observed on comparison withthe parent poly(caprolactone) polymer.