APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022;
Chicago
Session T18: Polymer and Polyelectrolyte Rheology II
11:30 AM–2:18 PM,
Thursday, March 17, 2022
Room: McCormick Place W-184D
Sponsoring
Unit:
DPOLY
Chair: Samanvaya Srivastava, UCLA
Abstract: T18.00012 : Linear viscoelastic behavior of supramolecular polymer networks from non-telechelic associative block copolymers
1:42 PM–2:18 PM
Abstract
Presenter:
Ruth Cardinaels
(KU Leuven)
Authors:
Ruth Cardinaels
(KU Leuven)
An-Sofie Huysecom
(KU Leuven)
Paula Moldenaers
(KU Leuven)
Supramolecular polymer networks formed from physically associating polymers are a class of materials with special features such as self-healing, stimuli-responsiveness and reprocessibility. They owe this to the presence of associating groups, either along the chain or at the chain ends. Associating behavior can originate from various non-covalent interactions such as hydrogen bonds, electrostatic interactions, metal-ligand bonds, etc. A thorough understanding of the network topology and its effect on the rheological properties can pave the way for the development of transient networks with designed elasticity and relaxation spectra. In the present work, the focus is on block copolymers that associate into micelles via hydrophobic blocks distributed along the chain. The network formation upon increasing temperature is mapped out with rheology, differential scanning calorimetry and turbidimetry. The concentration dependent elasticity and relaxation dynamics of the networks is characterized via linear rheology. Using a combinatorics approach, the Annable’s mechano-statistical model for telechelic triblock copolymers was extended to more general multiblock copolymers. The model requires input about the spatial distribution of the micelles and their size, which was derived from X-ray scattering. A comparison between experimental data and model results shows the model’s predictive capability for the concentration-dependent plateau modulus. The evolution of the high-frequency plateau modulus and hence the elasticity with concentration hints towards a change in network topology upon increasing concentration. The structure evolves from loop-dominated with limited elasticity at low concentrations to bridge-dominated and highly elastic at higher concentrations. On the other hand, the concentration dependence of the relaxation time(s) reveals the importance of superstructures such as superbridges and superloops, on the sticky Rouse-like relaxation dynamics of the network.