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Oppositely Charged, Stimuli-Responsive Anisotropic Nanoparticles for Colloidal Self-Assembly
journal contribution
posted on 2019-03-05, 00:00 authored by Eun Young Hwang, Jae Sang Lee, Dong Woo LimAnisotropic
nanoparticles (ANPs) composed of distinct compartments
are of interest as advanced materials because they offer unique physicochemical
properties controlled by polymer composition, distribution of functional
groups, and stimuli responsiveness of each compartment. Furthermore,
colloidal self-assembly of ANPs via noncovalent interactions between
compartments can create superstructures with additional functionality.
In this study, ANPs with two compartments composed of oppositely charged
and thermally responsive ternary copolymers were prepared using electrohydrodynamic
cojetting. One compartment was composed of poly(N-isopropylacrylamide-co-stearyl acrylate-co-allylamine), which is positively charged in aqueous solution
at pH 7, and the other compartment was composed of poly(N-isopropylacrylamide-co-stearyl acrylate-co-acrylic acid), which is negatively charged. The ANPs
were stabilized in aqueous solution by physical cross-linking because
of hydrophobic interactions between the 18-carbon alkyl chains of
their stearyl acrylate moieties and self-assembled into supracolloidal
nanostructures via electrostatic interactions. Colloidal self-assembly
and thermal responsiveness were controlled by compartment charge density
and solution ionic strength. The supracolloidal nanostructures exhibited
both the intrinsic temperature-responsive properties of the ANPs and
collective properties from self-assembly. These multifunctional, stimuli-responsive
nanostructures will be useful in a variety of applications, including
switchable displays, drug delivery carriers, and ion-sensitive gels.