A tapered copolymer is one kind of copolymer with unique microstructure, whereas a multi-arm tapered star copolymer has been rarely studied possibly due to the synthetic challenge. Herein, this work focuses on the investigation of eight-arm tapered star copolymers. Firstly, several tapered linear copolymers were prepared by the statistical anionic copolymerization of isoprene and styrene based on their reactivity difference in non-polar solvents. The tapered microstructures were confirmed by several techniques including proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and real-time ¹H NMR. Next, the tapered and diblock copolymers with similar molecular weight and volume fraction of PS were synthesized to compare the property difference by using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and rheology characterization. Moreover, the tapered linear copolymers with different ratios of soft and hard blocks were prepared by changing the feed ratios of the two monomers. It is found that the ratio of the soft and hard segments affects the thermal and mechanical properties of tapered copolymers to a large extent. Finally, octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) was introduced as a coupling agent to directly react with the tapered living copolymer chain, yielding three kinds of eight-arm tapered star copolymers 8[P(I-co-S)_x]-POSS (x = 1, 2, and 3) with different numbers of tapered blocks. The chemical structures and molecular weights of the resultant star copolymers were characterized. Furthermore, the results indicated that the introduction of the star-shaped structure could increase the thermal stability, while the increase of tapered block numbers might result in distinct thermal and viscoelastic behaviors of the copolymers.

中文翻译：

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阴离子共聚偶联反应制备八臂锥形星形共聚物的研究

锥形共聚物是一种具有独特微观结构的共聚物，而多臂锥形星形共聚物可能由于合成方面的挑战而很少被研究。在此，这项工作的重点是对八臂锥形星形共聚物的研究。首先，基于异戊二烯和苯乙烯在非极性溶剂中的反应活性差异，通过统计阴离子共聚制备了几种递变线型共聚物。通过质子核磁共振 ( ¹ H NMR)、凝胶渗透色谱 (GPC)、基质辅助激光解吸/电离飞行时间质谱 (MALDI-TOF MS) 和实时间¹核磁共振氢谱。接下来，通过热重分析 (TGA)、差示扫描量热法 (DSC) 和流变学表征，合成了具有相似分子量和 PS 体积分数的递变和二嵌段共聚物，以比较性能差异。此外，通过改变两种单体的进料比，制备了具有不同软硬嵌段比例的递变线型共聚物。发现软、硬链段的比例在很大程度上影响递变共聚物的热性能和力学性能。最后，引入八乙烯基多面体低聚倍半硅氧烷（OVPOSS）作为偶联剂与锥形活性共聚物链直接反应，得到三种八臂锥形星形共聚物8[P（I- co - S）_x]-POSS ( x = 1, 2, 和 3) 具有不同数量的锥形块。表征了所得星形共聚物的化学结构和分子量。此外，结果表明，星形结构的引入可以提高热稳定性，而锥形嵌段数的增加可能导致共聚物具有明显的热和粘弹性行为。