Complete Dynamic Phase Diagram of a Supramolecular Polymer

Nikolaos Burger , Gaelle Pembouong (1) , Laurent Bouteiller (1) , Dimitris Vlassopoulos (2) , Benoit Loppinet (3)

1 IPCM - Institut Parisien de Chimie Moléculaire
2 UOC - University of Crete [Heraklion]
3 FORTH-IESL - Institute of Electronic Structure and Laser

We revisit the equilibrium phase diagram of the much studied model supramolecular polymer, 2,4bis(2-ethylhexylureido)toluene (EHUT) in non-polar solvents, which had previously been studied at atmospheric pressure, and provide unambiguous evidence of a much richer behavior, characterized by four distinct regimes. Typically, two types of self-assembled structures are formed: tubes (filaments) at higher (lower) concentrations and lower (higher) temperatures, respectively. The tube structure forms viscoelastic solutions that had been characterized by rheology, however without detailed analysis of the experimental signals. Here, we combine rheology and microrheology to establish the complete dynamic phase diagram of EHUT in dodecane. It still comprises two structures, tubes and filaments, with the transition temperature being almost constant over the examined wide concentration range, as confirmed with the help of complementary differential scanning calorimetry measurements. The tubes are found to exist in three dynamic states with increasing concentration, unentangled, partially entangled and well-entangled, which are separated by iso-length lines. We present criteria for unambiguously identifying these phases and discuss their distinct concentration and temperature dependencies. The new, complete phase diagram may serve as guide for investigating other supramolecular polymers with tunable rheology and, more importantly, providing insights toward a universal description of one-dimensional selfassembled structures by linking this class of materials with the classic wormlike surfactant micelles, for which the partially and well-entangled regimes were recently elucidated.

Domaines: Matériaux

Nikolaos Burger, Gaelle Pembouong, Laurent Bouteiller, Dimitris Vlassopoulos, Benoit Loppinet. Complete Dynamic Phase Diagram of a Supramolecular Polymer. Macromolecules, 2022, 55 (7), pp.2609-2614. ⟨10.1021/acs.macromol.1c02508⟩. ⟨hal-03857181⟩