Christophe Schatz | Searcharxiv

arXiv2026

A Central Disulfide Junction Drives Transient Network Formation in Elastin-Like Polypeptides, Enabling Low-Concentration Hydrogels

The self-assembly of associative triblock copolymers composed of a central hydrophilic elastin-like polypeptide (ELP) block and short fatty acid end groups (C16) was investigated in aqueous solution. In one system, the ELP contains 80 pentapeptide units (C16-80-C16), whereas in the other two C16-ELP40 chains were oxidatively coupled through their terminal cysteine residues to form a central disulfide bond, yielding C16-(40)2-C16. Despite their nearly identical molecular weights and compositions, the two polymers exhibit markedly different self-assembly behaviors. C16-80-C16 forms large hydrophobic aggregates that remain kinetically trapped and do not develop a dynamically connected network. In contrast, C16-(40)2-C16 forms very small associative nodes with an aggregation number of only $\sim$3 chains. These nodes coexist with larger clusters and become dynamically interconnected at higher concentrations, leading to transparent hydrogels at concentrations as low as 2.5 wt %. Oscillatory rheology reveals a transient Maxwell network governed by a single relaxation process associated with the reversible association of the C16 end groups. SAXS, light scattering, cryo-TEM, and molecular modeling consistently support a model in which the central disulfide junction promotes transient network formation.

cond-mat.soft↗

arXiv2023

In situ monitoring of block copolymer self-assembly through controlled dialysis with light and neutron scattering detection

Solution self-assembly of amphiphilic block copolymers (BCs) is typically performed by a solvent-to-water exchange. However, BC assemblies are often trapped in metastable states depending on the mixing conditions such as the magnitude and rate of water addition. BC self-assembly can be performed under near thermodynamic control by dialysis, which accounts for a slow and gradual water addition. In this Letter we report the use of a specifically designed dialysis cell to continuously monitor by dynamic light scattering and small-angle neutron scattering the morphological changes of PDMS-b-PEG BCs self-assemblies during THF-to-water exchange. The complete phase diagrams of near-equilibrium structures can then be established. Spherical micelles first form before evolving to rod-like micelles and vesicles, decreasing the total developed interfacial area of self-assembled structures in response to increasing interfacial energy as the water content increases. The dialysis kinetics can be tailored to the time scale of BC self-assembly by modifying the membrane pore size, which is of interest to study the interplay between thermodynamics and kinetics in self-assembly pathways.

cond-mat.soft↗