Materials World Network: Electrochemical Processing of Nanoporous Structures for Superhydrophobic Materials and Polymer Imprinting

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The collaborative program with University of South Australia (UniSA) is aimed at designing and assessing the properties of nanoporous metal (NPM) architectures with controllable pore size and surface roughness. Electrochemical processing based on de-alloying of binary alloys and/or potential controlled galvanic displacement (PCD) will be employed to produce robust, surface-confined porous layers with lateral length-scales in the range of 5 nm to several microns. A subsequent surface modification of these layers (e.g. self-assembly of monolayers, silane chemisorption, plasma polymer deposition) will render these substrates superhydrophobic. Modified structures of that kind possess highly depressed adhesion properties and hence a significant chemical resistance. Also, the virtually non-existing contact angle hysteresis helps water droplets to easily roll off the superhybrophobic surface at small tilting angles. Another direction of this proposal emphasizes research aimed at developing of viable procedure for making polymer imprints from NPM structures confined in a thin surface layer. Potential applications of superhydrophobic NPM and their polymer replicas include self-cleaning windows, snow-repelling satellite antenna, pipes with reduced friction and rain-resistant transmission lines.The objectives of the American counterpart in this collaborative initiative are primarily focused on the development of protocols for synthesis of nanoporous Cu, Ag, Au, Pd and Pt, based on results of: (i) a fundamental study exploring tunable parameters that control the pore size during de-alloying in Cu-Au and Cu-Pt (one component dissolves) and Zn-Cu and Cu-Pd (both components dissolve) alloys; (ii) a fundamental investigation of the PCD process in Cu-Ag (immiscible) and Cu-Au (miscible) systems with emphasis on the factors controlling the evolution of surface morphology. The main scientific outcome will be manifested by the accomplishment of a comparative study of de-alloying and PCD processes aimed at identifying similarities and differences in view of controlling factors and resulting surface morphology. While the alloy processing will be carried out mainly by classical electrochemical methods, the structure, morphology and surface composition of the synthesized NPM will be characterized using scanning electron microscopy (SEM), scanning probe microscopy (SPM), Small Angle Neutron Scattering (SANS) and X-ray Photoelectron Spectroscopy (XPS)The research activity (co-funded by the Australian Research Council) is arranged in three strongly connected modules developed in collaboration with UniSA: (i) Fundamental investigation and development of optimal electrochemical pathways for synthesis of NPM, (ii) Exploration and implementation of efficient strategies for the hydrophobization of the NPM surfaces, and (iii) Development of procedures for fabricating polymer imprints that replicate the NPM surface topography. The award will support graduate students who will be exposed to an international research environment in summer-long student exchange initiatives with the counterpart institution.This award is co-supported by East Asia-Pacific Program of the NSF Office of International Science and Engineering, and by the Metals and Solid State Chemistry Programs of the Division of Materials Research.