High-Resolution Comonomer Sequencing of Blocky Brominated Syndiotactic Polystyrene Copolymers Using 13C NMR Spectroscopy and Computer Simulations,Macromolecules

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High-Resolution Comonomer Sequencing of Blocky Brominated Syndiotactic Polystyrene Copolymers Using 13C NMR Spectroscopy and Computer Simulations
Macromolecules ( IF 5.1 ) Pub Date : 2020-10-27 , DOI: 10.1021/acs.macromol.0c01630
Kristen F. Noble ₁ , Diego Troya ₁ , Samantha J. Talley ₁ , Jan Ilavsky ₂ , Robert B. Moore ₁

Affiliation

This work demonstrates the first high-resolution comonomer sequencing of Blocky brominated syndiotactic polystyrene (sPS-co-sPS-Br) copolymers based on pentad assignments of the quaternary carbon region of the nuclear magnetic resonance spectrum. Copolymers containing p-bromostyrene (Br-Sty) units were prepared in matched sets using postpolymerization bromination methods carried out in the heterogeneous gel state (Blocky) and homogeneous solution state (Random). Quantitative information from the quaternary carbon spectra, heteronuclear multiple bond correlation spectroscopy, electronic structure calculations, and simulated statistically random copolymers was correlated to confirm the carbon resonance assignments for all 20 possible pentad comonomer sequences. Using the experimental pentad sequence prevalences, a computer code was developed to simulate chains with microstructures typical of each sample as a means to visually represent the copolymer blockiness with quantitative precision. Based on the microstructure and distribution of run lengths in these chains, the simulations revealed that the Blocky copolymers contain a high degree of blockiness. By comparing the run lengths in the simulated chains to the average number of styrene units in a crystalline segment of sPS (found by small-angle X-ray scattering), copolymer crystallizability was predicted. For the simulated Blocky B-21% (21 mol % Br-Sty) chain, the probability of randomly selecting a styrene unit in a crystallizable block was 25.8%, while that in the simulated Random R-18% was zero, in excellent agreement with the experimental crystallization behavior measured by differential scanning calorimetry. These predictions confirmed that the simulated chains accurately represent the ensemble of chains in their respective copolymer samples. Furthermore, each simulated Blocky chain contained one or more long sPS blocks that paralleled the measured 38–40 styrene units spanning a crystalline segment within the sPS/CCl₄ gel. This finding affirmed that the long sPS segments originated from the precise lamellar structure within the heterogeneous gel morphology (i.e., block length is correlated with lamellar thickness). Overall, the ability to tailor the copolymer microstructure through control of the semicrystalline gel morphology opens the door to synthesizing ordered copolymers by postpolymerization functionalization processes with unprecedented levels of compositional control.

中文翻译：

使用¹³ C NMR光谱和计算机模拟对嵌段溴化间同立构聚苯乙烯共聚物进行高分辨率共聚单体测序

这项工作展示了基于核磁共振谱的季碳区的五单元组分配的嵌段溴化间同立构聚苯乙烯（sPS - co -sPS-Br）共聚物的第一个高分辨率共聚单体序列。含p的共聚物使用在异相凝胶态（Blocky）和均相溶液态（Random）中进行的后聚合溴化方法，以匹配的组合形式制备β-溴苯乙烯（Br-Sty）单元。来自季碳光谱，异核多键相关光谱，电子结构计算和模拟的统计随机共聚物的定量信息相互关联，以确认所有20种可能的五单元共聚单体序列的碳共振分配。使用实验五单元组的普遍性，开发了计算机代码来模拟具有每个样品的典型微结构的链，以可视化地定量表示共聚物的嵌段性。根据这些链条的行程长度的微观结构和分布，模拟表明，嵌段共聚物具有高度的嵌段性。通过将模拟链中的游程长度与sPS结晶段中苯乙烯单元的平均数目（通过小角度X射线散射发现）进行比较，可以预测共聚物的结晶性。对于模拟的块状B-21％（21 mol％Br-Sty）链，在可结晶嵌段中随机选择苯乙烯单元的概率为25.8％，而在模拟的随机R-18％中随机选择苯乙烯单元的概率为零，非常吻合通过差示扫描量热法测量的实验结晶行为。这些预测证实了模拟链准确地代表了它们各自共聚物样品中链的整体。此外，₄凝胶。该发现证实了长的sPS片段源自异质凝胶形态内的精确的层状结构（即，嵌段长度与层状厚度相关）。总体而言，通过控制半结晶凝胶形态来调整共聚物微观结构的能力为通过后聚合功能化过程以前所未有的组成控制水平合成有序共聚物打开了大门。

更新日期：2020-11-12

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