Ivana Vukovic

Supramolecular Route to Well-Ordered Metal Nanofoams

Metal nanofoams with a porosity above 50% v/v have recently attracted great interest in materials science due to their interesting properties. We demonstrate a new straightforward route to prepare such nanofoams using diblock copolymer-based PS-block-P4VP(PDP) supramolecules that self-assemble into a bicontinuous gyroid morphology, consisting of PS network channels in a P4VP(PDP) matrix. After dissolving the PDP, the P4VP collapses onto the PS struts and a free-standing bicontinuous gyroid template of 50-100 μm thickness and interconnected, uniformly sized pores is formed. The hydrophilic P4VP corona facilitates the penetration of water-based plating reagents into the porous template and enables a successful metal deposition. After plating, the polymer is simply degraded by heating, resulting in a well-ordered inverse gyroid nickel foam. Essential to this approach is the removal of only one part of the matrix (i.e., PDP). Therefore, the template accounts for 50% v/v or more. The porosity characteristics (amount, size of pores) can be tuned by selecting the appropriate copolymer and by adjusting the amount of PDP.

Nanoporous Network Channels from Self‐Assembled Triblock Copolymer Supramolecules

Supramolecular complexes of a poly(tert-butoxystyrene)-block-polystyrene-block-poly(4-vinylpyridine) triblock copolymers and less than stoichiometric amounts of pentadecylphenol (PDP) are shown to self-assemble into a core-shell gyroid morphology with the core channels formed by the hydrogen-bonded P4VP(PDP)complexes. After structure formation, PDP was removed using a simple washing procedure, resulting in well-ordered nanoporous films that were used as templates for nickel plating.

Shear-Induced Orientation of Gyroid PS-b-P4VP(PDP) Supramolecules

The phase behavior of block copolymer based supramolecular complexes polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and amphiphilic pentadecylphenol (PDP) molecules resembles the phase behavior of conventional block copolymers. Several PS-b-P4VP(PDP) complexes are found to self-assemble into gyroid nanostructures. Typically, the grains are randomly oriented with a maximal size of several micrometers. Here, the orientation of a gyroid PS-b-P4VP(PDP) complex upon shearing is reported. It is found that the (111) gyroid lattice direction orients parallel to the shear direction after only several seconds of large amplitude oscillatory shearing. Oriented gyroid complexes can be used as templates for the preparation of metal nanofoams with improved ordering with potentially superior properties.

Hierarchical self-assembly of two-length-scale multiblock copolymers.

The self-assembly in diblock copolymer-based supramolecules, obtained by hydrogen bonding short side chains to one of the blocks, as well as in two-length-scale linear terpolymers results in hierarchical structure formation. The orientation of the different domains, e.g. layers in the case of a lamellar-in-lamellar structure, is determined by the molecular architecture, graft-like versus linear, and the relative magnitude of the interactions involved. In both cases parallel and perpendicular arrangements have been observed. The comb-shaped supramolecules approach is ideally suited for the preparation of nanoporous structures. A bicontinuous morphology with the supramolecular comb block forming the channels was finally achieved by extending the original approach to suitable triblock copolymer-based supramolecules.

Textural properties of poly(glycidyl methacrylate): acid-modified bentonite nanocomposites

The aim of this study was to obtain enhanced textural properties of macroporous crosslinked copolymer poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) by synthesizing nanocomposites with acid-modified bentonite. Nanocomposites were obtained by introducing various amounts of acid-modified bentonite (BA) into the reaction system. All samples were characterized by attenuated total reflectance infrared spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), mercury intrusion porosimetry, and low temperature physisorption of nitrogen. The FTIR and TEM analysis confirmed incorporation of BA into the copolymer structure and the successful formation of nanocomposites. TEM images confirmed formation of nanocomposites having both intercalated and exfoliated acid-modified bentonite in copolymer matrix. A significant increase of specific surface area, pore volume, and porosity of the nanocomposites in comparison to the copolymer were obtained. The difference between textural properties of nanocomposites with different amounts of incorporated acid-modified bentonite was less prominent.

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the templates channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.