The continuous improvement
of synthesis leads to a great variety
in the internal architecture and functionality of colloidal hydrogels.
A majority of envisioned applications use microgels as colloidal building
blocks for layer formation at solid substrates. In this context, a
fundamental understanding of the influence of these substrates on
the internal structure and physical properties is essential. Especially,
the nanomechanical properties of adsorbed poly(N-isopropylacrylamide)
microgel particles are important for their application in cell cultivation,
functional surface coatings, and others. Furthermore, these properties
are closely related to the swelling behavior and the internal structure
and dynamics of these microgels. However, the number of methods that
are able to probe the viscoelasticity of adsorbed microgels over the
entire vertical particle profile is limited. Grazing incidence neutron
scattering techniques are suited to probe soft-matter samples with
limited sample volumes at planar solid substrates and allow a resolution
in the z-direction. We used neutron spin echo spectroscopy
under grazing incidence to access fast thermal fluctuations (10–9 s) over the entire vertical particle profile. Atomic
force microscopy nanoindentation was used to characterize the nanomechanical
properties of adsorbed microgel particles prepared by batch and continuous
monomer feeding methods. The resulting force maps revealed that batch
microgels were “hard” and heterogeneous in their Young’s
moduli, while the microgels from the continuous method were “soft”
and homogeneous. Finally, neutron spin echo spectroscopy under grazing
incidence revealed major differences in the vertical dynamic profile
of both types of microgels.