Low density polyethylene (LDPE) exhibits a complex branching architecture that is characterized by the numbers and lengths of the branches. In previous work, it has been demonstrated that comprehensive microstructural information on LDPE can only be obtained via multiple preparative fractionations and subsequent advanced analysis of the fractions. In this work, microstructural differences of LDPE with similar molar masses but different melt flow indexes are addressed. The samples are fractionated using the multiple preparative fractionation concept to generate narrowly distributed branch and molar mass fractions, respectively. The individual fractions are cross‐fractionated by stepwise recrystallization using successive self‐nucleation and annealing to obtain endotherms with multiple peaks (seeds). Each seed represents a population of chains with similar branching structure or crystallizable methylene sequences. The methylene sequence lengths (MSLs) and the seed contents of the seeds with the highest population are compared for fractions with similar fractionation characteristics. Fractions showing significant differences in their MSL and/or seed content are investigated further using advanced analytical techniques and 2D liquid chromatography (2D‐LC), to correlate MSL or seed content to the branching structure.

中文翻译：

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低密度聚乙烯支化分析中热分析的选择性

低密度聚乙烯（LDPE）表现出复杂的分支结构，其特征在于分支的数量和长度。在先前的工作中，已经证明，只有通过多次制备级分和随后对级分进行高级分析才能获得有关LDPE的全面微观结构信息。在这项工作中，解决了摩尔质量相似但熔体流动指数不同的LDPE的微观结构差异。使用多重制备分馏概念对样品进行分馏，分别产生狭窄分布的支链和摩尔质量分数。通过使用连续的自成核和退火的逐步重结晶，将各个馏分进行交叉分馏，以获得具有多个峰（种子）的吸热峰。每个种子代表具有相似分支结构或可结晶亚甲基序列的链种群。比较具有相似分馏特性的馏分，比较具有最高种群的种子的亚甲基序列长度（MSL）和种子含量。使用先进的分析技术和2D液相色谱（2D-LC）进一步研究了MSL和/或种子含量存在显着差异的馏分，以将MSL或种子含量与分支结构相关联。