Microstructure of Crystallizable α-Olefin Molecular Bottlebrushes: Isotactic and Atactic Poly(1-octadecene),Macromolecules

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Microstructure of Crystallizable α-Olefin Molecular Bottlebrushes: Isotactic and Atactic Poly(1-octadecene)
Macromolecules ( IF 5.1 ) Pub Date : 2018-01-24 00:00:00 , DOI: 10.1021/acs.macromol.7b02524
Carlos R. López-Barrón ₁ , Andy H. Tsou ₁ , Jarod M. Younker ₁ , Alexander I. Norman ₁ , Jonathan J. Schaefer ₁ , John R. Hagadorn ₁ , Joseph A. Throckmorton ₁

Affiliation

Isotactic and atactic poly(1-octadecene) (iPOD and aPOD) have been synthesized by organometallic coordinative insertion polymerization of 1-octadecene. Analyzing X-ray and neutron scattering data of POD melts identifies their bottlebrush structures as flexible rods where the rod length is the extended backbone length and rod radius is the side chain coil dimension. Upon cooling, both iPOD and aPOD melts crystallize by fully extending their coiled side chains to form orthorhombic alkane crystals in iPOD and nematically ordered rotator alkane crystals in aPOD, as determined by X-ray scattering and Raman spectroscopy. Molecular dynamics simulations of isotactic and atactic 48-mers of 1-octadecene were applied to define and verify melt and crystalline structures and scattering peak assignments, respectively. Modeling suggests that side chains of both crystallized isotactic and atactic PODs align at 70° and 160° to the 4/1 spiral backbone of equal probability, at an average of 115°, and POD chains pack in an antiparallel pattern. Large wheat-sheaf structural assembly of fibril bundles can be observed in aPOD, which render high opacity to these samples. Each of those fibrils is made of several bottlebrush molecules packed into a hexagonal lattice. Faster crystallization observed in iPODs hinders the formation of large crystallites, which results in translucent samples.

中文翻译：

可结晶的α-烯烃分子刷的微观结构：等规和无规聚（1-十八碳烯）

通过1-十八烯的有机金属配位插入聚合反应合成了等规和无规聚（1-十八碳烯）（iPOD和aPOD）。通过分析POD熔体的X射线和中子散射数据，可以确定其牙刷结构为柔性杆，其中杆长度是延伸的骨架长度，杆半径是侧链线圈尺寸。冷却后，通过X射线散射和拉曼光谱测定，iPOD和aPOD均通过完全延伸其卷曲的侧链以形成iPOD中的斜方烷烃晶体和aPOD中的向列有序的旋转烷烃晶体而熔融结晶。用1-十八烯的等规和无规48-mers的分子动力学模拟分别定义和验证熔体和晶体结构以及散射峰分配。建模表明，结晶的等规和无规POD的侧链平均概率为115°对齐于等概率的4/1螺旋骨架的70°和160°处，并且POD链以反平行模式排列。可以在aPOD中观察到原纤维束的大麦捆结构组装，这使这些样品具有很高的不透明性。这些原纤维中的每一个都是由填充成六边形格子的几个牙刷分子组成的。在iPOD中观察到的更快的结晶会阻碍大晶粒的形成，从而导致半透明的样品。从而使这些样品不透明。这些原纤维中的每一个都是由填充成六边形格子的几个牙刷分子组成的。在iPOD中观察到的更快的结晶会阻碍大晶粒的形成，从而导致半透明的样品。从而使这些样品不透明。这些原纤维中的每一个都是由填充成六边形格子的几个牙刷分子组成的。在iPOD中观察到的更快的结晶会阻碍大晶粒的形成，从而导致半透明的样品。

更新日期：2018-01-24

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