(607d) Shear and Extensional Rheology of Highly Entangled Cyclic Polymer in Melts and Solutions

Rheology of ring-like or circular polymers remains an area of active research due to the difficulty of making ring polymers of sufficient purity free of linear contaminants[1-4]. 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. Furthermore, synthesis in dilute solution results in small amounts of material being available for study. This problem has been overcome by reversible radical recombination polymerization (R³P) recently developed in the Puskas laboratories[5, 6]. R³P synthesis 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 melt synthesized by R³P of different molecular weights, solutions of PolyDODT as a function of concentration using both shear and extensional rheometry. Of interest is that the largest PolyDODT ring investigated to date has a molecular mass corresponding to approximately 190 entanglements in the linear counterpart. The extensional rheology behavior of cyclic PIB-disulfide and cyclic PolyDODT is compared with that of linear PIB with appropriate molecular weight and literature data for Polystyrene rings[4]. Linear and nonlinear shear responses of the cyclic PIB-disulfide melts, cyclic PolyDODT melts and solutions are also compared with literature results for nominally uncontaminated cyclic Polystyrenes [2, 7, 8]. The fragility and glass transition temperature of cyclic PolyDODT solutions is also studied.

1. McKenna, G., et al., A study of the linear viscoelastic properties of cyclic polystyrenes using creep and recovery measurements. Macromolecules, 1989. 22(4): p. 1834-1852.
2. Kapnistos, M., et al., Unexpected power-law stress relaxation of entangled ring polymers. Nat Mater, 2008. 7(12): p. 997-1002.
3. Doi, Y., et al., Re-examination of terminal relaxation behavior of high-molecular-weight ring polystyrene melts. Rheologica Acta, 2017. 56(6): p. 567-581.
4. Huang, Q., et al., Unexpected stretching of entangled ring macromolecules. Physical review letters, 2019. 122(20): p. 208001.
5. Rosenthal, E.Q., J.E. Puskas, and C. Wesdemiotis, Green polymer chemistry: Living dithiol polymerization via cyclic intermediates. Biomacromolecules, 2012. 13(1): p. 154-164.
6. Rosenthal-Kim, E.Q. and J.E. Puskas, Green polymer chemistry: Investigating the mechanism of radical ring-opening redox polymerization (R3P) of 3, 6-dioxa-1, 8-octanedithiol (DODT). Molecules, 2015. 20(4): p. 6504-6519.
7. Doi, Y., et al., Melt Rheology of Ring Polystyrenes with Ultrahigh Purity. Macromolecules, 2015. 48(9): p. 3140-3147.
8. Yan, Z.-C., et al., Linear and Nonlinear Shear Rheology of a Marginally Entangled Ring Polymer. Macromolecules, 2016. 49(4): p. 1444-1453.