mz400344e_si_001.pdf (343.07 kB)
Viscosity of Ring Polymer Melts
journal contribution
posted on 2016-02-18, 15:57 authored by Rossana Pasquino, Thodoris C. Vasilakopoulos, Youn Cheol Jeong, Hyojoon Lee, Simon Rogers, George Sakellariou, Jürgen Allgaier, Atsushi Takano, Ana R. Brás, Taihyun Chang, Sebastian Gooßen, Wim Pyckhout-Hintzen, Andreas Wischnewski, Nikos Hadjichristidis, Dieter Richter, Michael Rubinstein, Dimitris VlassopoulosWe
have measured the linear rheology of critically purified ring
polyisoprenes, polystyrenes, and polyethyleneoxides of different molar
masses. The ratio of the zero-shear viscosities of linear polymer
melts η0,linear to their ring counterparts η0,ring at isofrictional conditions is discussed
as a function of the number of entanglements Z. In
the unentangled regime η0,linear/η0,ring is virtually
constant, consistent with the earlier data, atomistic simulations,
and the theoretical expectation η0,linear/η0,ring = 2. In
the entanglement regime, the Z-dependence of ring
viscosity is much weaker than that of linear polymers, in qualitative
agreement with predictions from scaling theory and simulations. The
power-law extracted from the available experimental data in the rather
limited range 1 < Z < 20, η0,linear/η0,ring ∼ Z1.2±0.3,
is weaker than the scaling prediction (η0,linear/η0,ring ∼ Z1.6±0.3)
and the simulations (η0,linear/η0,ring ∼ Z2.0±0.3). Nevertheless,
the present collection
of state-of-the-art experimental data unambiguously demonstrates that
rings exhibit a universal trend clearly departing from that of their
linear counterparts, and hence it represents a major step toward resolving
a 30-year-old problem.