Paper Number
VP31 

Session
Pre-recorded Flash Presentations (virtual)

Title
Unravelling the transient network topology of hydrophobically associating multiblock copolymers and their resulting elasticity and relaxation times

Presentation Date and Time
All Week (Asynchronous) Any Time

Track / Room
Pre-recorded Presentation / Virtual

Authors (Click on name to view author profile)

  1. Huysecom, An-Sofie (KU Leuven, Chemical Engineering, Soft Matter, Rheology and Technology)
  2. Thielemans, Wim (KU Leuven Kulak, Chemical Engineering, Sustainable Materials lab)
  3. Cardinaels, Ruth (KU Leuven, Chemical Engineering)
  4. Moldenaers, Paula (KU Leuven, Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
An-Sofie Huysecom1, Wim Thielemans2, Ruth Cardinaels1 and Paula Moldenaers1
1Chemical Engineering, Soft Matter, Rheology and Technology, KU Leuven, Leuven, Belgium; 2Chemical Engineering, Sustainable Materials lab, KU Leuven Kulak, Kortrijk, Belgium

Speaker / Presenter 
Huysecom, An-Sofie

Keywords
gels; micelles; surfactants

Text of Abstract
Hydrophobically associating block copolymers are interesting materials for the design of physical hydrogels, and are often studied to gain fundamental understanding of transient polymer networks. In this contribution, linear rheology and small-angle X-ray scattering (SAXS) are combined to unravel the concentration dependent elasticity and relaxation dynamics of these networks. Whereas most studies use telechelic triblock copolymers as model systems, our study focuses on alternating multiblock copolymers having hydrophobic blocks distributed along the chain, thereby complicating their network behavior. Our experimental rheological data are compared to the predictions of a generalized transient network model, which we developed by adapting Annable's mechano-statistical model for telechelic triblock copolymers [1,2] to more general multiblock copolymers, based on a combinatorics approach. The spatial distribution of hydrophobic nodes as inferred from SAXS, is used as input for our transient network model to improve its descriptive strength. 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. The concentration dependence of the relaxation times, on the other hand, reveals the importance of superstructures such as superbridges and superloops, on the sticky Rouse-like relaxation dynamics of the network. A thorough understanding of the network topology and its effect on the rheological properties of the network, should pave the way for the development of transient networks with designed elasticity and relaxation spectra.

  1. T. Annable et al., Journal of Rheology, 1993, 37, 695
  2. T. Annable et al., Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1996, 112, 97