技术文章
测量应用案例-20220609
阅读:131 发布时间:2022-6-14
文献名:
Colloidal and polymeric contributions to the yielding of dense microgel suspensions
作者
:
M. A. Lara-Peña
ab
,
A. Licea-Claverie
c
,
I. Zapata-González
c
,
M. Laurati
a
a
Dipartimento di Chimica & CSGI, Università di Firenze, 50019 Sesto Fiorentino, Italy
b
División de Ciencias e Ingenierías, Universidad de Guanajuato, 37150 León, Mexico
c
Centro de Graduados e Investigación en Química del Tecnológico Nacional de México/Instituto Tecnológico de Tijuana, 22500 Tijuana, Mexico
摘要:
Hypothesis
Soft microgel
colloids
can be densely packed since particle networks can compress and interpenetrate. This evolution of the particle’s internal structure associated with packing is expected to determine the linear viscoelastic properties and the yielding behavior of dense suspensions of microgel colloids.
Experiments
We investigated the volume fraction-dependent linear and non-linear rheological response of suspensions of soft core-shell particles formed by a poly(
N
-isopropylacrylamide) (PNIPAM) microgel core and a thin poly(ethylene glycol) (PEG) shell.
Findings
The
linear viscoelasticity
of suspensions reveals a transition from a fluid to a jammed glass state. Increasing volume fraction within the jammed state, the linear
storage modulus
and the yield stress show distinct regimes associated with the evolution of particle contacts, which involve progressive compression and interpenetration of the shell and core. The yielding of jammed suspensions occurs in two-steps: At small strains jammed cages are rearranged, while full disentanglement of
interpenetrating networks
only occurs at
large deformations
and results in
fluidization
. Yield strains and stresses increase with increasing shear rate or frequency, suggesting a progressive dominance of the timescale associated with shear over that associated with the internal dynamics of the system.
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