Reentrant phase diagram and pH effects in cross-linked gelatin gels

TL;DR

This study uses Monte Carlo simulations to explore how pH influences gelation in cross-linked gelatin solutions, revealing a reentrant phase diagram where gelation is hindered at both low and high reactant concentrations.

Contribution

The paper introduces a lattice model simulation approach to analyze pH effects on gelatin gelation, uncovering a reentrant phase diagram and time ratio dependencies consistent with experiments.

Findings

Reentrant phase diagram with gelation hindered at low and high reactant concentrations.

Time ratio of bond formation depends on reactant reactivity.

Simulation results align with experimental observations.

Abstract

Experimental results have shown that the kinetics of bond formation in chemical crosslinking of gelatin solutions is strongly affected not only by gelatin and reactant concentrations but also by the solution pH. We present an extended numerical investigation of the phase diagram and of the kinetics of bond formation as a function of the pH, via Monte Carlo simulations of a lattice model for gelatin chains and reactant agent in solution. We find a reentrant phase diagram, namely gelation can be hindered either by loop formation, at low reactant concentrations, or by saturation of active sites of the chains via formation of single bonds with crosslinkers, at high reactant concentrations. The ratio of the characteristic times for the formation of the first and of the second bond between the crosslinker and an active site of a chain is found to depend on the reactant reactivity, in good agreement with experimental data.