Crystalline Regio-/Stereoregular Glycine-Bearing Polymers from ROMP: Effect of Microstructures on Materials Performances

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• 作者：Maosheng Li ; Fengchao Cui ; Yunqi LiYouhua Tao ; Xianhong Wang
• 刊名：Macromolecules
• 出版年：2016
• 出版时间：December 27, 2016
• 年：2016
• 卷：49
• 期：24
• 页码：9415-9424
• 全文大小：664K
• ISSN：1520-5835

文摘

Synthesis of amino acid or peptide-bearing polymers with controlled microstructures is still a long-going challenge in polymer chemistry in contrast to natural biopolymers with exactly controlled microstructures like proteins and DNA. Here, a series of new glycine-substituted cyclooctenes monomers were designed and synthesized. Ring-opening metathesis polymerizations (ROMP) of all 3-substituted monomers with Grubbs second-generation catalyst afford glycine-bearing polymers with high head-to-tail regioregularity and high trans-stereoregularity, whereas ROMP of 5-substituted monomers is neither regio- nor stereoselective. Theoretical study revealed that sterically cumbersome glycine substituent in the 3-position is crucial for the high regio- and stereochemistry in the polymerization. Of importance, differential scanning calorimetry and wide-angle X-ray scattering measurements show that unsaturated 3-substituted polymers are semicrystalline due to their high degrees of structure regularity and the strong hydrogen-bonding interactions between glycine side-chains. Such obvious crystallization behaviors before the saturation of the backbone will facilitate its future applications as biomimetic materials. Moreover, 3-substituted polymers with high trans-HT regularity exhibit much bigger water contact angle and higher cloud point than its random 5-substituted analogues, indicating that structure regularity of these glycine-bearing polymers can decide the surface hydrophilicity and thermoresponsive behaviors. These results demonstrate the dependence of glycine-bearing polymer properties on their microstructures. Finally, the less reactive internal trans-double bonds of the polymers undergo thiol–ene addition effectively, allowing the preparation of regiospecific glycine-bearing polymers with a range of features in a facile way.