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arXiv · 1807.01692

Relaxation dynamics, Softness and Fragility of Microgels with Interpenetrated Polymer Networks

Valentina Nigro·Barbara Ruzicka·Beatrice Ruta·Federico Zontone·Monica Bertoldo·Elena Buratti·Roberta Angelini
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Abstract

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.

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Valentina Nigro, Barbara Ruzicka, Beatrice Ruta, Federico Zontone, Monica Bertoldo, Elena Buratti, Roberta Angelini. 2018-07-04. Relaxation dynamics, Softness and Fragility of Microgels with Interpenetrated Polymer Networks. https://arxiv.org/abs/1807.01692

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