W. C. E. Schofield

Electroless deposition of multi-functional zinc oxide surfaces displaying photoconductive, superhydrophobic, photowetting, and antibacterial properties

Electroless growth of zinc oxide has been accomplished using palladium catalysts coordinated to pulsed plasma deposited poly(4-vinylpyridine) nanolayers. Four different and concurrent functional properties have been identified, which encompass photoconductivity, superhydrophobicity, photo-switchable wetting, and bacterial killing.

Impact of Picoliter Droplets on Superhydrophobic Surfaces with Ultralow Spreading Ratios

The impact of picoliter-sized water droplets on superhydrophobic CF(4) plasma fluorinated polybutadiene surfaces is investigated with high-speed imaging. Variation of the surface topography by plasmachemical modification enables the dynamics of wetting to be precisely controlled. Final spreading ratios as low as 0.63 can be achieved. A comparison of the maximum spreading ratio and droplet oscillation frequencies to models described in the literature shows that both are found to be much lower than theoretically predicted.

Controlled fragrant molecule release from surface-tethered cyclodextrin host-guest inclusion complexes.

β-cyclodextrin barrels can be tethered to solid surfaces using the Williamson ether synthesis reaction via an intermediate pulsed plasma deposited poly(4-vinylbenzyl chloride) linker layer. The loading and release of perfume molecules through host-guest inclusion complex formation with surface tethered β-cyclodextrin has been followed by infrared spectroscopy and quartz crystal microbalance measurements. Fragrance release lasts for several months and can be easily recharged.

A substrate-independent approach for bactericidal surfaces.

Existing methods for imparting antibacterial performance to solid surfaces tend to either be substrate-specific or rely upon leaching modes of action that cause ecological damage. An alternative approach is outlined comprising plasmachemical functionalization of solid surfaces with poly(4-vinyl pyridine) moieties and their subsequent activation (quaternization) with bromobutane to yield bactericidal activity. These bioactive surfaces can be applied to a host of different substrate materials and are easily regenerated by rinsing in water.

Surface Actuation of Smart Nanoshutters

Patterned polymer brush surfaces have been fabricated using the molecular scratchcard lithography technique, where a functional top nanolayer (acting also as a resist) is selectively removed using a scanning probe tip to expose underlying atom-transfer radical polymerization (ATRP) initiator sites. The lateral spreading of grafted polymer brush patterns across the adjacent functional resist surface can be reversibly actuated via solvent exposure. Effectively, this methodology provides a means for hiding/unveiling functional surfaces on the nanoscale.

A Substrate-Independent Lift-Off Approach for Patterning Functional Surfaces

A lift-off method for creating multifunctional patterned surfaces has been devised. It entails consecutive pulsed plasmachemical deposition of a reactive bottom layer and a protective top release layer. By way of example, a bottom/top layer combination comprising pulsed plasma deposited poly(glycidyl methacrylate)/poly(pentafluorostyrene) has been shown to display selective adhesive lift-off of the latter. Application of a prepatterned adhesive template yields well-defined arrays of reactive epoxide functionality surrounded by a passive fluoropolymer background or vice versa.

Tailoring the Density of Surface-Tethered Bottlebrushes

Surface-tethered bottlebrushes have been prepared by ATRP grafting of the macroinitiator brush backbone onto plasmachemical-deposited poly(vinylbenzyl chloride) initiator nanofilms followed by ATRP growth of the side chains (bristles). The surface density of bottlebrushes can be precisely tailored by varying the plasmachemical deposition parameters employed for producing the poly(vinylbenzyl chloride) initiator nanolayers. Lateral force scanning probe microscopy has shown that poly(glycidyl methacrylate)-graft-poly(sodium styrene sulfonate) bottlebrush-decorated surfaces give rise to an enhancement in lubrication.

Highly ion-conducting poly(ionic liquid) layers.

Highly ion-conducting poly(ionic liquid) thin films have been prepared in the absence of solvents utilizing a simple 2-step approach comprising pulsed plasmachemical deposition of 1-allylimidazole followed by vapour-phase quaternization with 1-bromobutane.

Rewritable and switching chiroptical supramolecular nanolayers

Attachment of chiral azobenzene chromophores to plasmachemical deposited structurally well-defined nanolayers yields supramolecular chiroptical properties. In the case of (S)-3-methyl-3-amino-1-(4′-cyano-4-azobenzene)pyrrolidine derivatized pulsed plasma poly(glycidyl methacrylate) nanofilms, circular dichroism measurements demonstrate enantiomeric toggling (switching) and longevity of chiroptical performance, which can be attributed to stable supramolecular helical configurations.

Photo-rewritable molecular printing

A simple method is described for photopatterning rewritable reactive groups onto solid surfaces. This comprises pulsed plasmachemical deposition of anhydride functionalised nanolayers, followed by molecular printing of nucleophile-containing inks. Subsequent UV lithography erasure and anhydride group reformation allows surface rewriting (ready for reaction with further nucleophile-containing molecular inks). Using this approach, it is possible to create either positive or negative image multifunctional rewritable patterned surfaces.