立构规整度对聚丙烯和聚（乙烯-丙烯）共聚物构象性质的影响,Macromolecules

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立构规整度对聚丙烯和聚（乙烯-丙烯）共聚物构象性质的影响
Macromolecules ( IF 5.1 ) Pub Date : 2018-08-28 00:00:00 , DOI: 10.1021/acs.macromol.8b01099
Panagiotis-Nikolaos Tzounis ₁ , Dora V. Argyropoulou ₁ , Stefanos D. Anogiannakis ₁ , Doros N. Theodorou ₁

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立构规整度是立构规整聚合物的最重要特征之一，它对形态和各种性质（如构象，热，流变，机械等）具有重大影响。在这项工作中，我们重点研究构象上的立构规整度，更具体地说单个聚丙烯（PP）均聚物以及嵌段和无规聚（乙烯-丙烯）共聚物链的无扰尺寸。通过应用Tzounis等人的单链蒙特卡罗算法，可以实现所有链的平衡。[大分子2017，50，4575-4587]。与以往的研究一致，我们发现立构规整度对PP均聚物的刚度有重要影响。特征比显示出非单调依赖于分数通过分析PP链骨架的扭转状态揭示了PP链上的内消旋二元组，这是由两种相互竞争的机制导致的。建立了一个简单的理论模型来描述聚（乙烯-嵌段-丙烯）共聚物的刚度对其丙烯含量及其PP嵌段的立构规整度的依赖性。最后，发现立构规整度和丙烯含量对用于模拟乙烯-丙烯单体（EPM）材料的聚（乙烯-无规-丙烯）链的刚度的影响与可用的旋转异构状态具有很好的定性一致性（RIS）模型预测。

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Tacticity Effect on the Conformational Properties of Polypropylene and Poly(ethylene–propylene) Copolymers

Tacticity is one of the most important features of stereoregular polymers, with significant impact on morphology and on a variety of properties such as conformational, thermal, rheological, mechanical, etc. In this work we focus on tacticity effects on the conformations and more specifically on the unperturbed dimensions of single polypropylene (PP) homopolymer and both block and random poly(ethylene–propylene) copolymer chains. The equilibration of all chains is achieved by applying the single-chain Monte Carlo algorithm of Tzounis et al. [Macromolecules2017, 50, 4575–4587]. In agreement with past studies, we find that tacticity has a significant effect on the stiffness of PP homopolymer. The characteristic ratio exhibits a nonmonotonic dependence on the fraction of meso dyads along the PP chains, which results from two competing mechanisms, revealed by analysis of the torsional states of the PP chain backbones. A simple theoretical model is developed to describe the dependence of the stiffness of poly(ethylene-block-propylene) copolymer on its propylene content and on the tacticity of its PP block. Finally, the effect of both tacticity and propylene content on the stiffness of poly(ethylene-random-propylene) chains, used to model ethylene–propylene monomer (EPM) materials, is found to be in very good qualitative agreement with available rotational isomeric state (RIS) model predictions.

更新日期：2018-08-28

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