To overcome difficulties associated with unlinked linear side products from their anionic synthesis, cyclic polymers were purified via fractionation using liquid chromatography at the critical condition.  Recently it has been shown that this approach yields reasonably pure cyclic polystyrenes  which at a molar mass corresponding to 12 entanglements do not exhibit a rubbery plateau, in contrast to their linear counterparts. This is suggestive of the (new) self-similar mechanism of stress relaxation of these macromolecules and of the conformation they adopt in the entanglement state (lattice animal).  Here, we extend this work in different directions: we use different chemistries, polyisoprene, polystyrene and poly(ethylene oxide).  Molar masses extend from unentangled regime to about 15 entanglements. We compare the as-synthesized and purified cyclic polymers, and blend the latter with linear polymers of the same molar mass over a wide range of concentrations. We compare results against mean-field model and scaling predictions as well as recent molecular dynamics simulations. In addition, a first attempt at studying knotted cyclic polymers of low molar mass is discussed. Finally, we critically discuss the results, also in view of earlier findings, and attempt at putting together the emerging picture of the physics of cyclic polymers (power-law stress relaxation, sensitivity to linear additives, scaling laws in blends) while discussing the open issues and challenges ahead.This work is part of a huge international effort involving the groups of J�lich (A. Bras, A. Wischnewski, W. Pyckhout-Hintzen, J. Allgaeir, D. Richter), Athens (G. Sakellariou, N. Hadjichristidis), Pohang (Y. C. Yeong, T. Chang), North Carolina (M. Rubinstein) and Crete (R. Pasquino, D. Vlassopoulos). It is supported in part by the EU (Softcomp, Dynacop).

Viscoelastic properties of critically purified cyclic polymers over a wide range of molecular weights

245th National Meeting (2013)

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