Interplay between shear loading and structural aging in a physical gel

TL;DR

This study investigates how shear stress influences the aging process in gelatin gels, revealing that stress accelerates structural stiffening through localized coil-to-helix transitions, with implications for understanding aging in soft materials.

Contribution

It demonstrates that shear stress affects gelatin gel aging via localized structural events, extending the phenomenology of aging in soft glassy materials.

Findings

Stress accelerates logarithmic stiffening in gelatin gels.

Aging dynamics slow down with increased geometric frustration.

The process involves elastically-aided coil-to-helix transitions.

Abstract

We show that the aging of the mechanical relaxation of a gelatin gel exhibits the same scaling phenomenology as polymer and colloidal glasses. Besides, gelatin is known to exhibit logarithmic structural aging (stiffening). We find that stress accelerates this process. However, this effect is definitely irreducible to a mere age shift with respect to natural aging. We suggest that it is interpretable in terms of elastically-aided elementary (coil$\to$helix) local events whose dynamics gradually slows down as aging increases geometric frustration.