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一种具有热稳定右旋螺旋构象的刚性手性树枝状聚合物。

A rigid, chiral, dendronized polymer with a thermally stable, right-handed helical conformation.

作者信息

Zhang Afang, Rodríguez-Ropero Francisco, Zanuy David, Alemán Carlos, Meijer E W, Schlüter A Dieter

机构信息

Institute of Polymers, Department of Materials, ETH Zürich, Wolfgang-Pauli-Straase 10, Zürich, Switzerland.

出版信息

Chemistry. 2008;14(23):6924-34. doi: 10.1002/chem.200800325.

Abstract

First- and second-generation dendronized polymethacrylates PG1 and PG2 carrying chiral 4-aminoproline-based dendrons were obtained on the half-gram scale in high molar masses (PG1: M(n)=5 x 10(6) g mol(-1), PG2: M(n)=1x10(6) g mol(-1)) by spontaneous (radical) polymerization of the corresponding vinyl macromonomers. NMR spectroscopic studies on PG2 together with its unprecedented high glass transition temperature (T(g)>200 degrees C, decomp) and structural parameters provided by atomistic MD simulations show this polymer to be rather rigid. Optical rotation and CD measurements revealed that PG2 adopts a helical conformation that remains unchanged over wide ranges of temperature and solvent polarity. It is also retained when the polymer is deprotected (and thus positively charged, de-PG2) at its terminal amino groups, by which the mass and steric demand of the dendrons is reduced by roughly 50 %. Molecular dynamics simulations on models of PG2 reveal its helical conformation to be right-handed, irrespective of backbone tacticity, and initial results also indicate that de-PG2 retains the right-handedness.

摘要

通过相应乙烯基大分子单体的自发(自由基)聚合反应,以半克规模获得了带有基于手性4-氨基脯氨酸树枝状分子的第一代和第二代树枝状聚甲基丙烯酸酯PG1和PG2,其摩尔质量较高(PG1:M(n)=5×10(6) g mol(-1),PG2:M(n)=1×10(6) g mol(-1))。对PG2进行的核磁共振光谱研究,连同其前所未有的高玻璃化转变温度(T(g)>200℃,分解)以及原子尺度分子动力学模拟提供的结构参数,表明该聚合物相当刚性。旋光和圆二色测量表明,PG2呈现螺旋构象,在很宽的温度和溶剂极性范围内保持不变。当聚合物在其末端氨基处脱保护(从而带正电荷,脱保护的PG2)时,这种构象也得以保留,此时树枝状分子的质量和空间需求大约降低了50%。对PG2模型进行的分子动力学模拟表明,无论主链规整度如何,其螺旋构象均为右手螺旋,初步结果还表明脱保护的PG2保留了右手螺旋性。

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