Direct measurement of entanglementformation in ultrahigh molecular weight polyethylene (UHMWPE)

Ultra-high molecular weight polyethylene (UHMWPE) with molecular weights in the order of 10^7 g/mol is characterized by a highly entangled state exhibiting enormous viscosities, which prohibit its melt processability. The single macromolecules form little single crystals containing one molecule only. These molecules naturally are unentangled giving rise to significantly lower melt viscosities. With ongoing time by interdiffusion the unentangled non equilibrium initial state evolves into the equilibrium entangled melt. This process offers the unique opportunity to observe the formation of entanglements as a function of time - after melting the huge molecules gradually entangle with each other, a process that takes several days. Presently, nothing is known about the molecular mechanisms of entanglement formation. NSE is a unique probe to follow this process on the scale of the entanglement itself and addresses the aspects like spatial evolution, heterogeneity. We propose such a study using fully deuterated UHMWPE co-crystallized with shorter hydrogenated PE that will act as a probe. The acquired knowledge will be crucial for designing the spinning process of ultra-strong PE fibers.