Primary Structure of Polyethylene Copolymers and Dominant Factors of Gelation

线性低密度聚乙烯（LLDPE）在有机溶剂（如癸烷、环戊烷和甲苯）中在室温附近转化为热可逆凝胶。每个结晶序列中的乙烯单元数的连接点尺寸估计为短链支化数（SCB）以及聚合物和溶剂之间的Flory-Huggins相互作用参数X12的函数。此外，假设马尔可夫过程，从11 C NMR测量估计连续乙烯单元数的重均长度L（E）w<13>，并将尺寸λ与一级结构长度L（E）w进行比较。获得了以下事实：1。当在不良溶剂中制备凝胶时，连接点尺寸ε变得大于长度L（E）w。而随着u参数的减小，粒子的大小近似等于长度L（E）w.随着SCB值的增加，颗粒尺寸逐渐减小，随着12个参数的增加，颗粒尺寸逐渐增大

A linear low-density polyethylene (LLDPE) in organic solvents (such as decane, cyclopentane, and toluene) converts to thermoreversible gel near room temperature. The junction point size ζ in number of ethylene units per crystalline sequence was estimated as a function of number of short-chain branching (SCB) as well as the Flory-Huggins interaction parameter X 12 between polymer and solvent. Moreover, weight-average length in number of consecutive ethylene units L(E)w was estimated from ^<13>C NMR measurement assuming the Markov process and the size ζ was compared with the primary structure length L(E)w. The following facts were obtained:1. The junction point size ζ became larger than the length L(E)w when the gel was prepared in a poor solvent. While, the size ζ was nearly equal to the length L(E)w with decreasing % u parameter.2. The size ζ decreased with increasing SCB, and increased with increasing 12 parameter