Preparation of colloidal molecules with temperature-tunable interactions from oppositely charged microgel spheres. Issue 42 (21st October 2019)

• Record Type: Journal Article
• Authors: Månsson, Linda K.; de Wild, Tym; Peng, Feifei; Holm, Stefan H.; Tegenfeldt, Jonas O.; Schurtenberger, Peter
• Is Part Of: Soft matter. Volume 15:Issue 42(2019)
• Page Start: 8512
• Page End: 8524
• Publication Date: 2019-10-21
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c9sm01779h
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Oppositely charged, soft, temperature-responsive PNIPAM microgels are used to assemble core–satellite-type colloidal molecules, thereby enabling convenient in situ tuning of size, volume fraction and inter-particle interactions with temperature. Abstract : The self-assembly of small colloidal clusters, so-called colloidal molecules, into crystalline materials has proven extremely challenging, the outcome often being glassy, amorphous states where positions and orientations are locked. In this paper, a new type of colloidal molecule is therefore prepared, assembled from poly( N -isopropylacrylamide) (PNIPAM)-based microgels that due to their well documented softness and temperature-response allow for greater defect tolerance compared to hard spheres and for convenient in situ tuning of size, volume fraction and inter-particle interactions with temperature. The microgels (B) are assembled by electrostatic adsorption onto oppositely charged, smaller-sized microgels (A), where the relative size of the two determines the valency ( n ) of the resulting core–satellite AB n -type colloidal molecules. Following assembly, a microfluidic deterministic lateral displacement (DLD) device is used to effectively isolate AB4 -type colloidal molecules of tetrahedral geometry that possess a repulsive-to-attractive transition on crossing the microgels' volume phase transition temperature (VPTT). These soft, temperature-responsive colloidal molecules constitute highly promising building blocks for the preparation of new materials with emergent properties, and their optical wavelength-size makes them especially interesting for optical applications.