Evidence for reptation in an entangled polymer melt

摘要: ENTANGLEMENTS, their nature and role in the dynamic properties of concentrated polymer solutions melts are not well understood1,2. The classical molecular view entanglements has been one rope-like intermolecular couplings at a number points along length molecule; molecules motion would drag past these couplings, essential effect being enhanced friction1,3. There growing realisation that this model is inadequate2,4,5. essence problem, rather, seems to be topological restrictions imposed on each molecule by its neighbours: movement given chain constrained entanglement or intersection with adjacent chains2. Theoretical treatment problem difficult6, met only limited success5. An interesting proposal regarding within entangled systems put forward De Gennes4,7: according this, confined virtual ‘tube’ defined locus intersections (or ‘entanglement’) (Fig. 1). wriggle, snake-like, own length, curvilinear propagation defects such as kinks ‘twists’8 tube; mode termed reptation4 (from reptile). Reptative clearly satisfies central requirement systems: non-crossability contours neighbours. In real melt environment any (that is, surrounding it) will itself change time. This because defining it themselves mobile. If reorganisation sufficiently slow then translational enclosed effectively (reptative). Consideration problem9 suggests case an system. One expects diffusion dominated reptation. no direct experimental evidence supporting physical reality systems. I report here results experiments polyethylene critically designed test reptation concept.