Shear and extensional rheology of highly entangled cyclic polymer in melts and solutions

Rheology of circular polymers remains an area of active research due to the difficulty of making ring polymers of sufficient purity free of linear contaminants. Past work has been limited to rings made in dilute solution and, consequently, have been limited to sizes of approximately 15 entanglements in the linear analog and small amounts of material being available for study. These problems have been overcome by reversible radical recombination polymerization (R³P) recently developed in Puskas laboratory. R³P can produce 10-100g scale circular polymer which opens new avenues of research. Here we have studied poly(3,6-dioxa-1,8-octanedithiol) (PolyDODT) and Polyisobutylene disulfide synthesized by R³P of different molecular weights. Of interest is that the largest PolyDODT ring investigated to date has a molecular mass corresponding to approximately 300 entanglements in the linear counterpart. The extensional rheology behavior of cyclic PIB-disulfide and cyclic PolyDODT is compared with that of linear PIB and literature data of Polystyrene ring. Linear and nonlinear shear responses of the cyclic PIB-disulfide melts, cyclic PolyDODT melts and solutions are compared with literature results published since 1980s.