Hydrogenated butadiene/ethene/1‐olefin terpolymers as model substances for short‐chain branched polyethylene

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Abstract
Poly[(butadiene‐alt‐ethene)‐co‐(butadiene‐alt‐1‐olefin)] terpolymers were synthesized by Ziegler‐Natta polymerization using VO(O‐neopentyl)2Cl/Al(i‐Bu)3 catalyst system in toluene. Variation of the 1‐olefin/ethene ratio in the monomer feed produces terpolymers with mixed units of butadiene‐alt‐ethene and butadiene‐alt‐1‐olefin. After hydrogenation one obtains model substances for LLDPE with a special distribution of methylene sequences between branching points. Differential scanning calorimetry (DSC) was used to determine the degree of crystallinity and the melting behavior. From the melting temperature region, the thickness distribution of the crystal lamellac, and thus the average number of C‐atoms between the alkyl branches, can be determined. From detailed X‐ray diffractometry, the mean crystallite size, the lattice distortions and the degree of crystallinity was determined for those products which show distinct reflections. The crystallization behavior can only be described by a three‐phase model.