Metallopolymer-Based Shape Anisotropic Nanoparticles

Abstract

The formation of nanostructured shape anisotropic nanoparticles from poly(ferrocenylsilane)-b-poly(2-vinylpyridine) (PFS-b-P2VP) block copolymers is presented. Ellipsoidal particles with an axially stacked lamellar structure and nanosheets with a hexagonal structure of PFS cylinders are obtained under neutral wetting conditions through the use of a mixed surfactant system during self-assembly. In contrast to traditional systems, the resulting particle structure is strongly influenced by crystallization of the PFS domains under colloidal confinement with lamella-forming PFS-b-P2VP block copolymers leading to cylindrical morphologies. A blending approach was developed to control this morphological change and by the addition of PFS homopolymers, ellipsoidal particles with a lamellar structure could also be obtained. Ultimately, the spatial control over two orthogonal functionalities was exploited to demonstrate morphology transitions for nanosheets upon the exposure to methanol as solvent for P2VP and FeCl 3 as a redox stimulus, opening up a variety of applications in the field of stimuli-responsive materials.T he unique performance of many natural materials is a direct result of the combination of multiple structural features in a synergistic fashion. 1 Highly specific functional properties are achieved by simultaneously controlling shape anisotropy, morphology, and stimuli-responsiveness from the nano-to the micrometer length scale. While this has long inspired researchers to strive for similar abilities in synthetic materials, approaching nature's extraordinary level of control remains a challenge. 2 One promising approach to such complex materials is based on controlling the self-assembly of block copolymers (BCPs) in nanoparticles upon solvent evaporation from emulsions. In such three-dimensional confinements, phase-separation gives access to unique structures and is dramatically influenced by the particle/water interface. One promising strategy to selectively tune the BCP self-assembly in these colloidal systems is based on using functional surfactants to adjust the surface energies between the different blocks and the surrounding medium. This facile and scalable methodology not only allows control over particle morphology, but also the overall shape. 3−12 The increasing availability of nanostructured shape anisotropic particles 13,14 is of significant interest as it opens up a variety of applications due to their unique properties, for example, in optics 15 or in cell internalization. 16 Recent examples include convex-shaped nanodiscs/-sheets with cylindrical domains 17,18 (perpendicular to the long axis) and striped ellipsoidal nanoparticles. 6,19 In such systems, both BCP domains are adjoining the particle surface, which enables access by chemical reagents present in the surrounding medium. In the case of stimuli-responsive BCPs, a specific response of a domain can lead to an overall change of the particles' structure. This has recently been demonstrated by the preparation of dynamic shape changing parti...

Polyferrocenylsilanes: synthesis, properties, and applications

“…338 This opens up applications as stimuliresponsive materials. 338 This opens up applications as stimuliresponsive materials.…”

“…221 For example, PI 320 -b-PFDMS 53 has a block ratio of 6 : 1 (PI : PFS) and self-assembles into cylindrical micelles in PI-selective hexanes, however PI 30 -b-PFDMS 60 , which has a block ratio of 1 : 2, forms tape-like platelet micelles (see Fig. 338 Nanosheets with a hexagonal array of PFS cylinders in a P2VP matrix were formed when a PFDMS-b-P2VP BCP was self-assembled under neutral wetting conditions (Fig. Although both materials have similar PFS block lengths, the significant difference in coronal block lengths has an obvious effect on the morphology formed.…”

Synthesis and Solution Self‐Assembly of Polyisoprene‐block‐poly(ferrocenylmethylsilane): A Diblock Copolymer with an Atactic but Semicrystalline Core‐Forming Metalloblock

“…337 This opens up these materials for applications as stimuli-responsive materials. Fluorescent multiblock comicelles present a novel approach towards the preparation of encoded nanomaterials with potential applications in high density data storage materials and biological diagnostics.…”

“…336 Shape anisotropic nanoparticles with intrinsic nanostructures within the particles have been reported by self-assembly of an amphiphilic PFS BCP in an aqueous mixed surfactant system. 337 Nanosheets with a hexagonal array of PFS cylinders in a P2VP matrix were formed when a PFDMS-b-P2VP BCP was self-assembled under neutral wetting conditions (Figure 36a). Self-assembly of the PFS BCP with additional PFS homopolymer under the same conditions formed ellipsoidal particles with an axially stacked lamellar structure ( Figure 36b).…”

Chelation‐Induced Polymer Structural Hierarchy/Complexity in Water

“…Müller and co‐workers reported hierarchical co‐assembly via solvophobic interactions. Winnik and Hawker illustrated structural hierarchy/complexity using crystallization‐induced self‐assembly. Multidimensional hierarchical self‐assembly of amphiphilic cylindrical micelles using a crystallizable poly(ferrocenyldimethylsilane) core‐forming block was reported by Manners and co‐workers .…”