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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: Crystallization, Nucleation, Self Assembly I (joint session CPP/DY, organized by CPP)

CPP 34.3: Talk

Wednesday, March 9, 2016, 10:15–10:30, H42

How realistic are *random coils* in HD-PE? Analysis of the closeness of the packing. — •Heinz H. W. Preuss — Hameln

In a previous talk (CPP 6.7 Spring Meeting 2015) was demonstrated evidence of chain folding in HD-PE after slow cooling from the melt. With an analysis of the density and closeness of Packing including a model experiment with balls close wound with a clothes line one can learn that the density of the melt can be reached only with a high portion (at 80 %) of chain segments beeing nearly close and parallel neigbouring but not with *random coils* understood as balls packed with an entangeled molecular chain. The conformation in the melt should be near to the conformation in the crystal what is easy to be understood with the existence of folded chains in the melt. Compared with the crystal structure in the melt the molecules have 27,6 % more volume and 8,5 % more average distance available for mobility and flexibility. The random coil remains an important abstract mathematical tool, but should not be missinterpreted as if an arbitrarily coiled line could be a correct model of polymer molecules in a melt.