Impact of a minority enantiomer on the polymerization of alanine-based isocyanides with an oligothiophene pendant
Impact of a minority enantiomer on the polymerization of alanine-based isocyanides with an oligothiophene pendant
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少数对映体对带有低聚噻吩侧链的丙氨酸基异氰化物聚合的影响
DOI：
10.1039/c6py01351a
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发表时间：
2016
影响因子：
4.6
通讯作者：
K.-i.
中科院分区：
文献类型：
--
作者：
Ikai;T.; Wada;Y.; Takagi;Y.; Shinohara;K.-i.
使用镍催化剂对带有五喹噻吩侧基的 L-和 D-丙氨酸基对映体异氰化物进行（共）聚合。通过色谱、圆二色光谱、原子力显微镜（AFM）和全原子分子动力学模拟研究了单体进料比对聚合动力学和所得聚合物结构（包括分子量和主链构象）的影响。对于对映体纯单体的聚合，链增长反应几乎在几分钟内完成，并产生分子量超过 1 × 107 g mol−1 的单手螺旋多异氰化物。通过高分辨率AFM直接观察微米级长度的聚合物单链。当聚合原料含有 9 mol% 对映共聚单体时，单体消耗率和聚合物分子量下降至约 10%。分别是对映体纯系统中获得的值的七分之一和百分之一。我们还发现，仅含有 2 mol% 对映体单元的聚合物根本不采用螺旋结构，而是完全无规螺旋构象。实验和模拟研究表明，超过 50 个重复单元的长程纯手性序列上的协同分子内相互作用对于维持螺旋构象是必要的。这些相互作用包括酰胺基团之间的氢键以及五喹啉噻吩侧链之间的 π-π 堆积。这种协同作用在插入的单体和不断增长的链端之间提供了有利的相互作用，这可能对促进单体与镍中心的配位并加速聚合反应发挥重要作用。
L- and D-Alanine-based enantiomeric isocyanides bearing a quinquethiophene pendant group were (co)polymerized using a nickel catalyst. The influences of the monomer feed ratio on the polymerization kinetics and the resulting polymer structures, including molecular weights and backbone conformations, were investigated by chromatography, circular dichroism spectroscopy, atomic force microscopy (AFM) and all-atom molecular dynamics simulations. For polymerization of the enantiopure monomer, the chain growth reaction was almost complete within a few minutes and yielded a one-handed helical polyisocyanide with a molecular weight of more than 1 × 107 g mol−1. The polymer single chains of micrometer-order length were directly observed by high-resolution AFM. When the polymerization feed contained 9 mol% of the antipode comonomer, the monomer consumption rate and polymer molecular weight decreased to ca. one seven-hundredth and one one-hundredth of the values obtained in the enantiopure system, respectively. We also found that the polymer containing only 2 mol% of antipode units did not adopt a helical structure at all and possessed a totally random-coil conformation. The experimental and simulation study revealed that cooperative intramolecular interactions over a long-range homochiral sequence of more than 50 repeating units were necessary for maintaining a helical conformation. These interactions included hydrogen-bonding between amide groups, and π–π stacking between quinquethiophene pendants. This cooperativity provided a favorable interaction between an inserted monomer and a growing chain end, which would likely play an important role to promote the monomer coordination to the nickel center and to accelerate the polymerization reaction.
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影响因子：
5.5
作者：
K. Onitsuka;Tomoko Mori;Mari Yamamoto;F. Takei;Shigetoshi Takahashi
通讯作者：
K. Onitsuka;Tomoko Mori;Mari Yamamoto;F. Takei;Shigetoshi Takahashi
种族和光学活性4-甲基-1-己炔的聚合
影响因子：
2.5
作者：
F. Ciardelli;E. Benedetti;O. Pieroni
通讯作者：
O. Pieroni
甲基丙烯酸苯基-2-吡啶基-邻甲苯基甲酯的不对称和对映体选择性聚合
DOI：
10.1295/polymj.19.897
发表时间：
1987
期刊：
影响因子：
--
作者：
E. Yashima;Y. Okamoto;K. Hatada
通讯作者：
K. Hatada
调整 PS-嵌段共聚物的性能及其组装成聚合物囊泡。
影响因子：
3.4
作者：
H. M. de Hoog;D. M. Vriezema;M. Nallani;Suzanne M Kuiper;J. Cornelissen;A. Rowan;R. Nolte
通讯作者：
R. Nolte
DOI：
10.1007/bf00696533
发表时间：
1992
期刊：
影响因子：
--
作者：
K. Matyjaszewski
通讯作者：
K. Matyjaszewski