Uniaxial extensional rheology of well-characterized comb polymers

H. Lentzakis, D. Vlassopoulos*, D. J. Read, H. Lee, T. Chang, P. Driva, N. Hadjichristidis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


We present a detailed systematic investigation of the transient uniaxial extensional response of a series of well-characterized, anionically synthesized comb polystyrenes and polyisoprenes. The comb architecture consists of a linear chain backbone with multiple branches of equal molar mass, and represents an excellent model branched polymer. The linear viscoelastic response has been studied already in great detail. Our results indicate that the strain hardening becomes more important as the Hencky strain rate is increased. In general, the larger the number of entanglements of the segments between branches and/or of the branches, the stronger the strain hardening and the smaller the characteristic rate for its onset. The key molecular parameter appears to be the number of entanglements per branch. By varying it, one can tailor the amount and onset of strain hardening. This can be rationalized by accounting for the combined effect of backbone tube dilation and extra friction, brought about by the branches. In fact, we define an effective "stretch time" of the comb as the timescale for stretch relaxation along the dilated backbone tube when accounting for the large friction that comes from the branches and suggest that extension hardening occurs at rates equal to or greater than its inverse. The good comparison of this prediction to experimental data is a promising guide toward a universal framework for understanding the effects of branches on extensional rheology, and hence providing some insight into the behavior of long-chain branched polyolefins.

Original languageEnglish (US)
Pages (from-to)605-625
Number of pages21
JournalJournal of Rheology
Issue number2
StatePublished - Mar 2013

Bibliographical note

Funding Information:
The authors thank J. Roovers for generously providing the PS combs used in this work. They acknowledge support by the EU (ITN DYNACOP 214627), NRF (SRC R11-2008-052-03002), and WCU (R31-2008-000-10059-0). They thank M. Kempf and D. Auhl for help in the early stages of the experimental work, as well as F. Snijkers, R. Pasquino, and C. Das for helpful discussions. They also acknowledge the hospitality of O. Hassager in DTU where some test measurements were taken with the FSR with the help of Q. Huang, and the assistance of L. Hawke (Leeds) with running the pom-pom code.


  • Comb polymer
  • Dynamic dilution
  • Strain hardening
  • Stretch time
  • Uniaxial extension

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • General Materials Science


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