首页> 外文期刊>Journal of Polymer Science, Part A. Polymer Chemistry >Grafting of functional nitroxyl free radicals to polyolefins as a tool to postreactor modification of polyethylene-based materials with control of macromolecular architecture
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Grafting of functional nitroxyl free radicals to polyolefins as a tool to postreactor modification of polyethylene-based materials with control of macromolecular architecture

机译:将功能性亚硝酰基自由基接枝到聚烯烃上,作为在高分子结构控制下对聚乙烯基材料进行后反应改性的工具

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摘要

Nitroxyl radicals were used as functionalizing agents during the free radical postreactor modification process of polyolefins carried out in the melt. The 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (HO-TEMPO) and the 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (BzO-TEMPO) free radicals were successfully grafted onto a polyethylene-based material (ethylene-co-1-octene copolymer) by coupling reaction with polymer macroradicals; these last were formed by H-abstraction through peroxide addition. The macromolecular structure of the functionalized polyolefins was assessed by 1H-NMR, FTIR spectroscopy, and SEC measurements which were used to evidence the grafting site, to evaluate the grafting level and to highlight the occurrence of chain extension through crosslinking side reactions. Indeed the use of proper model compounds allowed the preparation of accurate FTIR calibration curves for the quantitative determination of the functionalization degree. Besides the high temperature SEC analysis highlighted that this fast and simple coupling reaction between macroradicals and nitroxyl free radicals grants the grafting of functionalities onto the polyolefin backbone by contemporarily preventing the side reactions liable of the structure and MW modification of the pristine polymer.
机译:在熔融物中进行的聚烯烃的自由基后反应器改性过程中,将硝基羟自由基用作官能化剂。 4-羟基-2,2,6,6-四甲基哌啶-1-氧基(HO-TEMPO)和4-苯甲酰氧基-2,2,6,6-四甲基哌啶-1-氧基(BzO-TEMPO)的自由基是通过与聚合物基自由基的偶联反应成功地接枝到聚乙烯基材料(乙烯-共-1-辛烯共聚物)上;这些最后是通过过氧化物添加H提取而形成的。通过1 H-NMR,FTIR光谱和SEC测量来评估官能化聚烯烃的大分子结构,这些结构可用于证明接枝位点,评估接枝水平并突出通过交联副反应发生扩链。实际上,使用适当的模型化合物可以制备准确的FTIR校准曲线,以定量确定功能化程度。除了高温SEC分析,还强调了大自由基与硝基氧基自由基之间的这种快速而简单的偶联反应,通过同时防止了可能造成原始聚合物结构和MW改性的副反应,使官能团接枝到了聚烯烃主链上。

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