Synthesis and Characterization of Cyclic and Linear Helical Poly(α-peptoid)s by N-Heterocyclic Carbene-Mediated Ring-Opening Polymerizations of N-Substituted N-Carboxyanhydrides
Synthesis and Characterization of Cyclic and Linear Helical Poly(α-peptoid)s by N-Heterocyclic Carbene-Mediated Ring-Opening Polymerizations of N-Substituted N-Carboxyanhydrides
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DOI：
10.1002/bip.21597
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发表时间：
2011-01-01
期刊：
影响因子：
2.9
通讯作者：
Zhang, Donghui
中科院分区：
文献类型：
--
作者：
Guo, Li;Li, Jinhai;Zhang, Donghui
环状聚（α-类肽）[a.k.a.通过N-杂环卡宾介导的N-取代羧基氰（（N）R-NCA）开环聚合，合成了具有手性芳香侧链[R =（R）-或（S）-CHMePh]的聚（N-R-甘氨酸）]。它们的线性类似物已通过伯胺引发的相应（N）R-NCA的聚合来制备。通过这些方法可以容易地获得聚合物分子量（MW）在4-15 kg mol（-1）范围内和低MW分布（多分散指数（PDI）< 1.15）的聚[（R）/（S）-N-CHMePh-甘氨酸]。它们的高分子量类似物没有得到由于竞争形成的环状低聚物的物种，导致分子内转酰胺。特性粘度测量证实了通过两种方法制备的聚合物之间的结构差异，并揭示了环状和线性聚[（S）-N-CHMePh-甘氨酸]在0.1M LiBr/二甲基甲酰胺（DMF）溶液中表现为无规卷曲聚合物。圆二色性分析表明，环状和线性聚（α-类肽）的保留聚脯氨酸I螺旋构象，类似于以前报道的线性低聚物。差示扫描量热分析表明，环状和线性聚[（S）-N-CHMePh-甘氨酸]都是无定形的，环状聚合物的玻璃化转变温度（T（g）= 122 ℃）显著高于具有相同MW的线性类似物的玻璃化转变温度（T（g）= 112 ℃）。这些结果与不存在链端一致，导致聚合物具有降低的链段迁移率。(C)2011 Wiley Periodicals，Inc. Biopolymers（Pept Sci）96：596-603，2011.
Cyclic poly(alpha-peptoid)s [a.k.a. poly(N-R-glycine)] with chiral aromatic side-chains [R = (R)- or (S)-CHMePh] have been synthesized by N-heterocyclic carbene-mediated ring-opening polymerization of N-substituted N-carboxyanhydrides ((N)R-NCA). Their linear analogs have been prepared by primary amine-initiated polymerization of the corresponding (N)R-NCA. Poly [(R)/(S)-N-CHMePh-glycine] with polymer molecular weights (MWs) in the range of 4-15 kg mol(-1) and low MW distribution (Polydispersity index (PDI) < 1.15) can be readily accessed by these methods. Their high MW analogs were not obtained due to the competitive formation of cyclic oligomeric species that result from intramolecular transamidation. Intrinsic viscosity measurements confirm the architectural difference between the polymers prepared by the two methods and reveals that both cyclic and linear poly[(S)-N-CHMePh-glycine]s behave as random-coil polymers in 0.1M LiBr/Dimethylformamide (DMF) solution. Circular dichroism analysis suggests that the cyclic and linear poly(alpha-peptoid)s retain polyproline I helix conformations, analogously to previously reported linear oligomers. Differential scanning calorimetry analysis reveals that cyclic and linear poly[(S)-N-CHMePh-glycine] are both amorphous with the glass transition temperature of the cyclic polymers (T(g) = 122 degrees C) being notably higher than that of the linear analogs (T(g) = 112 degrees C) with identical MW These results are consistent with the absence of chain ends, causing the polymers to have reduced segmental mobilities. (C) 2011 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 96: 596-603, 2011.