Microgels are elastic and deformable particles with a hybrid nature between that of polymers and colloids and unconventional behaviors 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 the 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 behavior, 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
Relaxation dynamics, softness, and fragility of microgels with interpenetrated polymer networks
Valentina Nigro
;Barbara Ruzicka
;Monica Bertoldo;Elena Buratti;Roberta Angelini
2020
Abstract
Microgels are elastic and deformable particles with a hybrid nature between that of polymers and colloids and unconventional behaviors 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 the 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 behavior, 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 theoryFile | Dimensione | Formato | |
---|---|---|---|
prod_418516-doc_161061.pdf
solo utenti autorizzati
Descrizione: relaxation dynamics, softness, and fragility of microgels with interpenetrated polymer networks
Tipologia:
Versione Editoriale (PDF)
Licenza:
NON PUBBLICO - Accesso privato/ristretto
Dimensione
1.44 MB
Formato
Adobe PDF
|
1.44 MB | Adobe PDF | Visualizza/Apri Richiedi una copia |
1807.01692.pdf
accesso aperto
Descrizione: Relaxation dynamics, softness, and fragility of microgels with interpenetrated polymer networks
Tipologia:
Documento in Pre-print
Licenza:
Altro tipo di licenza
Dimensione
839.92 kB
Formato
Adobe PDF
|
839.92 kB | Adobe PDF | Visualizza/Apri |
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.