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Phase Behavior of Bowl‐Shaped Colloids: Order and Dynamics in Plastic Crystals and Glasses
Author(s) -
Meijer JanneMieke,
Crassous Jérôme J.
Publication year - 2018
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201802049
Subject(s) - materials science , plastic crystal , crystallization , polystyrene , chemical physics , phase transition , phase (matter) , colloid , anisotropy , phase diagram , crystal (programming language) , colloidal crystal , yukawa potential , volume fraction , glass transition , condensed matter physics , chemistry , optics , physics , thermodynamics , polymer , composite material , organic chemistry , particle physics , computer science , programming language
Charged fluorescent bowl‐shaped colloids consisting of a polystyrene core surrounded by a poly( N ‐isopropylmethacrylamide) shell are obtained by nanoengineering spherical composite microgels. The phase diagram of these soft bowl‐shaped colloids interacting through long‐range Yukawa‐type interactions is investigated using confocal laser scanning microscopy. The bowl‐shaped structure leads to marked differences in phase‐behavior compared to their spherical counterpart. With increasing number density, a transition from a fluid to a plastic crystal phase, with freely rotating particles, followed by a glass‐like state is observed. It is found that the anisotropic bowl shape frustrates crystallization and slows down crystallization kinetics and causes the glass‐like transition to shift to a significantly lower volume fraction than for the spheres. Quantitative analysis of the positional and orientational order demonstrates that the plastic crystal phase exhibits quasi‐long range translational order and orientational disorder, while in the disordered glass‐like phase the long‐range translational order vanishes and short‐range rotational order appears, dictated by the specific bowl shape. It is further shown that the different structural transitions are characterized by decoupling of the translational and orientational dynamics.