Microgels are elastic and deformable particles with a hybrid nature between that of polymers and colloids and unconventional behaviours with respect to hard colloids. We investigated the dynamics of a soft microgel made of interpenetrated polymer networks of PNIPAM and PAAc by means of coherent X-ray and light scattering techniques. By varying the particle softness through PAAc content we can tune at wish the fragility of IPN microgels. Interestingly we find the occurrence of a dynamical crossover at a critical weight concentration which leads to an evolution of the structural relaxation time from a super-Arrhenius to a slower than Arrhenius behaviour, a minimum for the shape parameter of intensity autocorrelation function and the emerging of distinct anomalous mechanisms for particle motion. This complex phenomenology can be described by a Fickian diffusion at very low concentrations, an effective non Fickian anomalous diffusion at intermediate values and a ballistic motion well described within the Mode Coupling Theory.
@article{arxiv.1807.01692,
title = {Relaxation dynamics, Softness and Fragility of Microgels with Interpenetrated Polymer Networks},
author = {Valentina Nigro and Barbara Ruzicka and Beatrice Ruta and Federico Zontone and Monica Bertoldo and Elena Buratti and Roberta Angelini},
journal= {arXiv preprint arXiv:1807.01692},
year = {2023}
}