Softness plays a key role in determining
the macroscopic properties
of colloidal systems, from synthetic nanogels to biological macromolecules,
from viruses to star polymers. However, we are missing a way to quantify
what the term “softness” means in nanoscience. Having
quantitative parameters is fundamental to compare different systems
and understand what the consequences of softness on the macroscopic
properties are. Here, we propose different quantities that can be
measured using scattering methods and microscopy experiments. On the
basis of these quantities, we review the recent literature on micro-
and nanogels, i.e. cross-linked polymer networks swollen in water,
a widely used model system for soft colloids. Applying our criteria,
we address the question what makes a nanomaterial soft? We discuss
and introduce general criteria to quantify the different definitions
of softness for an individual compressible colloid. This is done in
terms of the energetic cost associated with the deformation and the
capability of the colloid to isotropically deswell. Then, concentrated
solutions of soft colloids are considered. New definitions of softness
and new parameters, which depend on the particle-to-particle interactions,
are introduced in terms of faceting and interpenetration. The influence
of the different synthetic routes on the softness of nanogels is discussed.
Concentrated solutions of nanogels are considered and we review the
recent results in the literature concerning the phase behavior and
flow properties of nanogels both in three and two dimensions, in the
light of the different parameters we defined. The aim of this review
is to look at the results on micro- and nanogels in a more quantitative
way that allow us to explain the reported properties in terms of differences
in colloidal softness. Furthermore, this review can give researchers
dealing with soft colloids quantitative methods to define unambiguously
which softness matters in their compound.
HCU performed at the point of care by FDs with remote expert support interpretation using a web-based system is feasible, rapid and useful for detecting significant echocardiographic abnormalities and reducing the number of unnecessary echocardiographic studies.
We report results of small angle neutron scattering measurements made on sodium polystyrene sulfonate in aqueous salt solutions. The correlation length (ξ) and osmotic compressibility are measured as a function...
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