TY - JOUR
T1 - Anisotropic Hollow Microgels That Can Adapt Their Size, Shape, and Softness
AU - Nickel, Anne C.
AU - Scotti, Andrea
AU - Houston, Judith E.
AU - Ito, Thiago
AU - Crassous, Jérôme
AU - Pedersen, Jan Skov
AU - Richtering, Walter
PY - 2019/11
Y1 - 2019/11
N2 - The development of soft anisotropic building blocks is of great interest for various applications in soft matter. Furthermore, such systems would be important model systems for ordering phenomena in fundamental soft matter science. In this work, we address the challenge of creating hollow and anisotropically shaped thermoresponsive microgels, polymeric networks with a solvent filled cavity in their center that are swollen in a good solvent. Sacrificial elliptical hematite silica particles were utilized as a template for the synthesis of a cross-linked N-isopropylacrylamide (NIPAm) shell. By varying the amount of NIPAm, two anisotropic microgels were synthesized with either a thin or thick microgel shell. We characterized these precursor core-shell and the resulting hollow microgels using a combination of light, X-ray, and neutron scattering. New form factor models, accounting for the cavity, the polymer distribution and the anisotropy, have been developed for fitting the scattering data. With such models, we demonstrated the existence of the cavity and simultaneously the anisotropic character of the microgels. Furthermore, we show that the thickness of the shell has a major influence on the shape and the cavity dimension of the microgel after etching of the sacrificial core. Finally, the effect of temperature is investigated, showing that changes in size, softness, and aspect ratio are triggered by temperature.
AB - The development of soft anisotropic building blocks is of great interest for various applications in soft matter. Furthermore, such systems would be important model systems for ordering phenomena in fundamental soft matter science. In this work, we address the challenge of creating hollow and anisotropically shaped thermoresponsive microgels, polymeric networks with a solvent filled cavity in their center that are swollen in a good solvent. Sacrificial elliptical hematite silica particles were utilized as a template for the synthesis of a cross-linked N-isopropylacrylamide (NIPAm) shell. By varying the amount of NIPAm, two anisotropic microgels were synthesized with either a thin or thick microgel shell. We characterized these precursor core-shell and the resulting hollow microgels using a combination of light, X-ray, and neutron scattering. New form factor models, accounting for the cavity, the polymer distribution and the anisotropy, have been developed for fitting the scattering data. With such models, we demonstrated the existence of the cavity and simultaneously the anisotropic character of the microgels. Furthermore, we show that the thickness of the shell has a major influence on the shape and the cavity dimension of the microgel after etching of the sacrificial core. Finally, the effect of temperature is investigated, showing that changes in size, softness, and aspect ratio are triggered by temperature.
KW - anisotropic colloids
KW - anisotropic microgels
KW - Microgels
KW - small-angle neutron scattering
KW - soft matter
KW - thermoresponsive polymer
UR - http://www.scopus.com/inward/record.url?scp=85073869913&partnerID=8YFLogxK
U2 - 10.1021/acs.nanolett.9b03507
DO - 10.1021/acs.nanolett.9b03507
M3 - Letter
C2 - 31613114
AN - SCOPUS:85073869913
SN - 1530-6984
VL - 19
SP - 8161
EP - 8170
JO - Nano Letters
JF - Nano Letters
IS - 11
ER -