TY - JOUR
T1 - Softness mapping of the concentration dependence of the dynamics in model soft colloidal systems
AU - Li, Qi
AU - Peng, Xiaoguang
AU - Chen, Dongjie
AU - McKenna, Gregory B.
N1 - Publisher Copyright:
© 2021 Elsevier Inc.
PY - 2022/1
Y1 - 2022/1
N2 - The dynamics of a series of soft colloids comprised of polystyrene cores with poly(N-isopropylacrylamide) (PNIPAM) coronas was investigated by diffusing wave spectroscopy (DWS). The modulus of the coronas was varied by changing the cross-link density and we were able to interpret the results within a hard-soft mapping framework. The soft, swellable particle properties were modeled using an extended Flory-Rehner theory and a Hertzian pair potential. Following volume fraction jumps, softness effects on the concentration dependence of dynamics were determined, with a ‘soft colloids make strong glass-forming liquid’-type of behavior observed close to the nominal glass transition volume fraction, φg. Such behavior from the current systems cannot be fully explained by the osmotic deswelling model alone. However, inspired by the soft-hard mapping from Schmiedeberg et al, [Europhys. Lett. 2011, 96 (3), 36010] we estimated effective hard-sphere diameters and achieved a successful mapping of the α-relaxation times to a master curve below φg. Above φg, the curves no longer collapse but show strong deviations from a Vogel-Fulcher type of divergence onto soft jamming plateaux. Our results provide evidence that osmotic deswelling itself cannot fully explain the observed dynamics. Softness also plays an important role in the dynamics of soft, concentrated colloids.
AB - The dynamics of a series of soft colloids comprised of polystyrene cores with poly(N-isopropylacrylamide) (PNIPAM) coronas was investigated by diffusing wave spectroscopy (DWS). The modulus of the coronas was varied by changing the cross-link density and we were able to interpret the results within a hard-soft mapping framework. The soft, swellable particle properties were modeled using an extended Flory-Rehner theory and a Hertzian pair potential. Following volume fraction jumps, softness effects on the concentration dependence of dynamics were determined, with a ‘soft colloids make strong glass-forming liquid’-type of behavior observed close to the nominal glass transition volume fraction, φg. Such behavior from the current systems cannot be fully explained by the osmotic deswelling model alone. However, inspired by the soft-hard mapping from Schmiedeberg et al, [Europhys. Lett. 2011, 96 (3), 36010] we estimated effective hard-sphere diameters and achieved a successful mapping of the α-relaxation times to a master curve below φg. Above φg, the curves no longer collapse but show strong deviations from a Vogel-Fulcher type of divergence onto soft jamming plateaux. Our results provide evidence that osmotic deswelling itself cannot fully explain the observed dynamics. Softness also plays an important role in the dynamics of soft, concentrated colloids.
KW - Colloids
KW - Dynamics
KW - Glass
KW - Osmotic deswelling
KW - Soft jamming
KW - Soft-hard mapping
UR - http://www.scopus.com/inward/record.url?scp=85111334684&partnerID=8YFLogxK
U2 - 10.1016/j.jcis.2021.07.089
DO - 10.1016/j.jcis.2021.07.089
M3 - Article
C2 - 34332413
AN - SCOPUS:85111334684
SN - 0021-9797
VL - 605
SP - 398
EP - 409
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
ER -