jp9b07754_si_002.mov (2.53 MB)
A Droplet-Based Microfluidics Route to Temperature-Responsive Colloidal Molecules
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posted on 2019-10-17, 15:04 authored by Feifei Peng, Linda K. Månsson, Stefan H. Holm, Somnath Ghosh, Göran Carlström, Jérôme
J. Crassous, Peter Schurtenberger, Jonas O. TegenfeldtSmall
clusters of spherical colloids that mimic real molecules,
so-called colloidal molecules, hold great promise as building blocks
in bottom-up routes to new materials. However, their typical hard
sphere nature has hampered their assembly into ordered structures,
largely due to a lack of control in the interparticle interactions.
To provide easy external control of the interactions, the present
work focuses on the preparation of colloidal molecules from temperature-responsive
microgel particles that undergo a transition from a soft repulsive
to a short-range attractive state as their characteristic volume phase
transition temperature (VPTT) is crossed. Preparation of the colloidal
molecules starts with the use of a droplet-based microfluidics device
to form highly uniform water-in-oil (W/O) emulsion droplets containing,
on average and with a narrow distribution, four microgels per droplet.
Evaporation of the water then leads to the formation of colloidal
molecule-like clusters, which can be harvested following cross-linking
and phase transfer. We use a mixture of two types of microgels, one
based on poly(N-isopropylacrylamide) (PNIPAM) and
the other on poly(N-isopropylmethacrylamide) (PNIPMAM),
to prepare bicomponent colloidal molecules, and show that the difference
in VPTT between the two allows for induction of attractive interparticle
interactions between the PNIPAM interaction sites at temperatures
in between the two VPTTs, analogous to the interactions among patchy
biomacromolecules such as many proteins.