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Long-Chain Branch Measurement in Substantially Linear Ethylene Polymers by 13C NMR with Halogenated Naphthalenes as Solvents

Zhou, Zhe, Baugh, Dan, Fontaine, Philip P., He, Yiyong, Shi, Zhi, Mukhopadhyay, Sukrit, Cong, Rongjuan, Winniford, Bill, Miller, Matt
Macromolecules 2017 v.50 no.20 pp. 7959-7966
carbon, catalysts, chemical structure, ethylene, naphthalenes, nuclear magnetic resonance spectroscopy, optical properties, polymers, solvents, stable isotopes, viscoelasticity
Substantially linear ethylene polymers (SLEPs) are important commercial products which are used in various applications such as packaging, electrical insulation, toys, pipes, footwear, roofing, automotive, fabrics, and much more. SLEPs can be produced using molecular catalysts which can lead to long chain branching (LCB). The amount of LCB has an influence on viscoelastic properties which affect film production and processing as well as mechanical and optical properties. Thus, it is important to accurately measure LCB content. ¹³C NMR is one of the methods that have been used to characterize LCB. It is quite challenging to measure LCB with ¹³C NMR in the presence of short chain branches (SCBs) longer than four carbons due to the overlap of LCB signals with SCB signals. In this paper, we describe the use of halogenated naphthalenes as suitable solvents to separate ¹³C signals related to LCB from SCB. The new method presented here allows for better quantification of LCB in polymer samples with a diverse array of branching types.