Self-Assembly of Janus Cylinders into Hierarchical Superstructures

Abstract

We present in-depth studies of the size tunability and the self-assembly behavior of Janus cylinders possessing a phase segregation into two hemicylinders. The cylinders are prepared by cross-linking the lamella-cylinder morphology of a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) block terpolymer. The length of the Janus cylinders can be adjusted by both the amplitude and the duration of a sonication treatment from the micro- to the nanometer length. The corona segregation into a biphasic particle is evidenced by selective staining of the PS domains with RuO(4) and subsequent imaging. The self-assembly behavior of these facial amphiphiles on different length scales is investigated combining dynamic light scattering (DLS), small-angle neutron scattering (SANS), and imaging procedures. Cryogenic transmission electron microscopy images of the Janus cylinders in THF, which is a good solvent for both blocks, exhibit unimolecularly dissolved Janus cylinders with a core-corona structure. These results are corroborated by SANS measurements. Supramolecular aggregation takes place in acetone, which is a nonsolvent for polystyrene, leading to the observation of fiber-like aggregates. The length of these fibers depends on the concentration of the solution. A critical aggregation concentration is found, under which unimolecularly dissolved Janus cylinders exist. The fibers are composed of 2-4 Janus cylinders, shielding the inner insoluble polystyrene hemicylinder against the solvent. Herein, the SANS data reveal a core-shell structure of the aggregates. Upon deposition of the Janus cylinders from more concentrated solution, a second type of superstructure is formed on a significantly larger length scale. The Janus cylinders form fibrillar networks, in which the pore size depends on the concentration and deposition time of the sample.

Colour-tunable fluorescent multiblock micelles

“…Although several reports have described the preparation of cylindrical nanostructures with segregated fluorescent regions 12,14,39 , this represents the first example of such structures where full control over the length, number and emission colour of the fluorescent regions can be achieved. Although a wide range of nanoscale morphologies are accessible through BCP self-assembly, relatively few examples exist of methods for the preparation of non-centrosymmetric, non-spherical structures 40,41 . However, non-centrosymmetric micelles can be accessed by CDSA using a unidirectional growth approach, by the generation of seed micelles capable of further epitaxial growth at one end only 42 Fig.…”

Design Advances in Particulate Systems for Biomedical Applications

“…[ [258][259][260] Spherical Polystyrene Poly(propylene carbonate) Poly(9,9-dioctylfl uorene-2,7-diyl-co-bis-N , Nfl uorene-2,7-diyl-co-bis-N , Nphenyl-1,4-phenylenedi amine) (PFB) Poly(9,9-dioctylfl uorene-2,7-diyl-cobenzothiadiazole) (F8BT) Miniemulsion, phase separation…”

Alignment of cylindrical colloids near chemically patterned substrates induced by critical Casimir torques

“…Highly elliptical and (sphero-) cylindrical colloids are widely used in present research and may have applications in new materials [45,46]. A diverse set of elongated particles such as cylindrical micelles [47], block copolymers [48], the mosaic tobacco virus [49], and carbon nanotubes [50,51] is experimentally available. The (self-) alignment of the latter type of particles can also be used in biological cell analyses [52], and may lead to improvements in different technologies such as solar cells [53], energy storage [54], or liquid crystal displays [55].…”

“…The experimental fabrication of such particles is of research interest in itself [48,58,59], as is the theoretical understanding of the interactions between spherical [60,61] or between non-spherical Janus particles [62,63], because they are considered to be promising building-blocks for selfassembling materials.…”