Paper Number
IM9 

Session
Inverse Problems and Material Design

Title
Tailoring rheological response via thickness and macromolecular architecture

Presentation Date and Time
October 9, 2017 (Monday) 2:45

Track / Room
Track 5 / Crestone B

Authors (Click on name to view author profile)

1. Vlassopoulos, Dimitris (FORTH-IESL)
2. Costanzo, Salvatore (FORTH-IESL)
3. Yan, Zhi-Chao (FORTH-IESL)
4. Parisi, Daniele (FORTH-IESL)

Author and Affiliation Lines (in printed abstract book)
Dimitris Vlassopoulos, Salvatore Costanzo, Zhi-Chao Yan, and Daniele Parisi
FORTH-IESL, HERAKLION, Greece

Speaker / Presenter 
Vlassopoulos, Dimitris

Text of Abstract
Since entanglements represent the key feature of long polymers, altering their number and strength is a route to tailor rheology and processability. A known example is the constraint release effect in homopolymer mixtures. Here, we discuss two recent examples where the synergy of molecular rheology and polymer synthesis can possibly advance further the field: (i) Macromolecular thickness decreases the number of entanglements and makes polymers akin to supersoft elastomers, as demonstrated with bottlebrushes. Alternatively, dendronized polymers (DPs), comprising a backbone grafted with dendrons, exhibit orientational order, weak shear thinning and elasticity, which can vary by adjusting the degree of polymerization and dendron generation, allowing to span the gap from wormlike polymers to colloidal molecules. Selective introduction of strong associating groups into the first generation of the DPs leads to unusual linear and nonlinear viscoelastic properties, which can be completely damped by introducing additional branching that causes an effective molecular shielding for these groups. (ii) Entangled ring polymers are known to exhibit self-similar stress relaxation and a zero-shear viscosity much lower than that of their linear counterparts. Yet, their mixtures, with low fraction of rings (say 20%) exhibit higher viscosity. We present a systematic study of linear and nonlinear shear rheology with both symmetric and asymmetric mixtures, in order to elucidate the phenomenology of this and propose ways to selectively modify the viscosity of homopolymer melts via entropic mixing. These examples show the power of macromolecular engineering in manipulating the rheology of polymeric systems. Work in collaboration with A. D. Schlueter, T. Chang, J. Roovers, P. Lutz and M. Kalyva.