Polymers with high molecular weights have superior properties, such as enhanced impact and chemical resistance. While these properties can be achieved by converting a thermoplastic into a thermoset, this can prevent polymers from further processing as thermosets cannot be melted and moulded without damaging their internal structure. Therefore, increasing the molecular weight of a polymer without losing the ability to process it is of utmost importance. Polyethylene (PE), the most commonly produced plastic in the world, is comprised of strong C–C and C–H bonds, which makes its controlled chain extension challenging to achieve. Herein, we report a novel, solution-based method for the modification of PE chains using commercially available, low-cost organic peroxides in solvents such as dichlorobenzene and tert-butylbenzene. To the best of our knowledge, this is the first solution-based methodology for PE modification through the incorporation of long chain PE branches by using organic peroxides. The effects of the modification reactions were extensively investigated using rheology, differential scanning calorimetry, small/wide angle X-ray scattering, size exclusion chromatography and NMR spectroscopy, and model studies were performed with n-dodecane to confirm the formation of branched moieties. The enhanced mechanical properties of the materials were demonstrated using rheology, where the modified polymers show significantly increased stiffness and higher viscosities. This is attributed to reactions between the PE chains to form branched structures, thus increasing both the molecular weight of the feedstock and the number of entanglements within the polymer microstructure. This methodology enables the properties of PE to be tailored, providing a shortcut for the development of new PE grades and formulations as its applications continue to grow in developing technologies such as 3D printing, artificial joints and soft robotics.

中文翻译：

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通过溶液态过氧化物改性来增强聚乙烯性能的通用改性策略

高分子量聚合物具有优异的性能，例如增强的抗冲击性和耐化学性。虽然这些特性可以通过将热塑性塑料转化为热固性塑料来实现，但这可能会阻止聚合物进一步加工，因为热固性塑料无法在不损坏其内部结构的情况下熔化和成型。因此，在不损失加工能力的情况下增加聚合物的分子量至关重要。聚乙烯 (PE) 是世界上最常生产的塑料，由强 C-C 和 C-H 键组成，这使得其受控扩链难以实现。在此，我们报告了一种基于溶液的新颖方法，使用市售的低成本有机过氧化物在二氯苯和叔丁基苯等溶剂中对 PE 链进行改性。据我们所知，这是第一个基于解决方案的 PE 改性方法，通过使用有机过氧化物掺入长链 PE 支链。使用流变学、差示扫描量热法、小/广角 X 射线散射、尺寸排阻色谱和 NMR 光谱广泛研究了改性反应的影响，并使用正十二烷进行了模型研究以确认支化部分的形成。使用流变学证明了材料机械性能的增强，其中改性聚合物显示出显着增加的刚度和更高的粘度。这是由于 PE 链之间的反应形成支化结构，从而增加了原料的分子量和聚合物微结构内的缠结数量。这种方法使 PE 的性能能够定制，为开发新的 PE 牌号和配方提供了捷径，因为它的应用在 3D 打印、人工关节和软机器人等开发技术中不断增长。