Royston W. Paynter

Superhydrophobic Aluminum Alloy Surfaces by a Novel One-Step Process

A simple one-step process has been developed to render aluminum alloy surfaces superhydrophobic by immersing the aluminum alloy substrates in a solution containing NaOH and fluoroalkyl-silane (FAS-17) molecules. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements have been performed to characterize the morphological features, chemical composition and superhydrophobicity of the surfaces. The resulting surfaces provided a water contact angle as high as ∼162° and a contact angle hysteresis as low as ∼4°. The study indicates that it is possible to fabricate superhydrophobic aluminum surfaces easily and effectively without involving the traditional two-step processes.

Chemical Nature of Superhydrophobic Aluminum Alloy Surfaces Produced via a One-Step Process Using Fluoroalkyl-Silane in a Base Medium

Various surface characterization techniques were used to study the modified surface chemistry of superhydrophobic aluminum alloy surfaces prepared by immersing the substrates in an aqueous solution containing sodium hydroxide and fluoroalkyl-silane (FAS-17) molecules. The creation of a rough micronanostructure on the treated surfaces was revealed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS) confirmed the presence of low surface energy functional groups of fluorinated carbon on the superhydrophobic surfaces. IRRAS also revealed the presence of a large number of OH groups on the hydrophilic surfaces. A possible bonding mechanism of the FAS-17 molecules with the aluminum alloy surfaces has been suggested based on the IRRAS and XPS studies. The resulting surfaces demonstrated water contact angles as high as ~166° and contact angle hystereses as low as ~4.5°. A correlation between the contact angle, rms roughnesses, and the chemical nature of the surface has been elucidated.

One-Step Deposition Process to Obtain Nanostructured Superhydrophobic Thin Films by Galvanic Exchange Reactions

Superhydrophobic thin films of silver were fabricated on copper substrates by galvanic ion exchange reactions in a one-step process by immersing copper substrates in silver nitrate solution containing fluoroalkylsilane in different quantities. The X-ray diffraction (XRD) analyses confirmed the formation of silver films on copper substrates and the fractal-like morphological features of the silver films were confirmed using scanning electron microscopy (SEM). The contact angle of water on these surfaces is found to be greater than 165°, demonstrating water repellency with water drops rolling off the surfaces. The X-ray photoelectron spectroscopy (XPS) depth profile confirms the presence of fluorine in the silver films.

Spectroscopic studies of soluble poly(N-alkyl anilines) in solution and in casted films

Abstract Absorption spectra for poly(N-alkylanilines), prepared in perchloric acid, in acetonitrile solution and in the form of thin films casted on ITO from acetonitrile solution, are presented and compared. Spectroelectrochemical studies of poly(N-alkylanilines) in the form of casted films and in acetonitrile solution were also performed. The casted polymers films on ITO dipped in 1 M perchloric acid reversibly changed their colors from pale yellow green to deep blue when the applied potentials were varied between 0.0 and 1.0 V vs Ag/AgCl reference electrode. Similar results were obtained when solutions of poly(N-alkylanilines) in acetonitrile were polarized between 0.0 and 1.0 V. The electronic structures of poly(N-alkylanilines) are discussed.

Polymerization and properties of poly(3-chlorodiphenylamine): a soluble electrochromic conducting polymer

Abstract Poly(3-chlorodiphenylamine) was prepared by electrochemical and chemical polymerization in acetonitrile solutions. The as-synthesized polymers are soluble in organic solvents and concentrated acid and exhibited a room temperature electrical conductivity of 1.6 × 10−3 S cm−1. Electropolymerized and solution cast films are electroactive and displayed reversible colour changes when cycled in organic or acid electrolytes between 0.0 V and 1.3 V versus Ag AgCl .

Processible poly(N-alkyl diarylamine) conducting polymers. Synthesis and spectroelectrochemistry

Abstract Chemical oxidation of N-alkyl diphenylamines N-alkylDPA and N-alkyl phenyl napthylamines N-alkylPNA (alkyl = methyl, ethyl, butyl and hexyl) using copper tetrafluoroborae in acetonitrile solution produced high molecular weight poly(N-alkyl diarylamines) polyers – a new class of conducting polymers intermediated tween poly(aniline) and poly(p-phenylene) or poly(p-naphthaene) – which are soluble in organic solvents (e.g. dimethyl formamide, dimethyl sulfoxide and N-methyl pyrrolidnone). The assynthesized poly(N-alkyl diarylamines) with doping levels lower than 25% exhibited room temperature conductivities in the range of 10 −5 to 10 −7 S/cm. Uniform and adherent polymer films, which were casted on ITO glass from dimethylformamide solutions, showed multiple color changes when cycled in 1.0 M LiClO 4 /acetonitrile solution between 0.0 and 1.0 V vs Ag/AgCl.

The ROVT Elan Valved Biplex Conduits for the Reconstruction of the Right Ventricular Outflow Tract

The reconstruction of the right ventricular outflow tract (RVOT) system represents a considerable challenge for both manufacturers and surgeons because the patients requiring this type of devices have a very diverse set of anatomical challenges that can lead to complications and subsequent early device failures. We conducted an indepth investigation of a porcine-valve conduit explanted from a patient following an adverse event. A control device was analyzed as a reference. The rapid aging of the porcine valve in the right side of the heart together with major thrombus formation raises several questions. The difficulties encountered with materials used and also the design features of the conduits are once again highlighted. This group of patients continues to increase in number due to success in the surgical outcomes in early childhood. Therefore, there is a greater demand for an appropriate device. However, much work is still needed to achieve this goal, and the best approach to achieving success remains unanswered.

The triplex BioValsalva prostheses to reconstruct the aortic valve and the aortic root

The Bentall procedure introduced in 1968 represents an undisputed cure to treat multiple pathologies involving the aortic valve and the ascending thoracic aorta. Over the years, multiple modifications have been introduced as well as a standardized approach to the operation with the goal to prevent long-term adverse events. The BioValsalva prosthesis provides a novel manner to more efficiently reconstruct the aortic valve together with the anatomy of the aortic root with the implantation of a valved conduit. This prosthesis comprises three sections: the collar supporting the valve; the skirt mimicking the Valsalva, which is suitable for the anastomoses with the coronary arteries; and the main body of the graft, which is designed to replace the ascending aorta. The BioValsalva prosthesis allows the Bentall operation to be used in patients whose aortic valve cannot be spared.

Polymer Masks Fabrication by Micropatterning Surfaces of Composite Polymer Coatings

Abstract Micropatterning of surfaces has been demonstrated using composite polymer coatings of PS and PMMA of equal molecular weights in different volume proportions with varying surface topographies on silicon surfaces. The creation of PMMA masks with various surface morphological features has also been demonstrated by removal of PS from the composite coatings using cyclohexane. Atomic force microscopy (AFM) investigations revealed that the surface pattern and the dimensions of these masks significantly changed with the change in the volume proportions of each homopolymer. The composite coatings of 20/80 vol% PS/PMMA, 50/50 vol% PS/PMMA, and 80/20 vol% PS/PMMA resulted in PMMA masks with holes (depth ∼300 nm), wrinkles (height ∼350 nm) and pillars (height ∼600 nm), respectively. Surface compositional analysis carried out using FTIR and XPS investigations confirmed the presence of polymer coatings of PS, PMMA and PS/PMMA. XPS investigations also confirmed the successful removal of PS from the PMMA mask by showing the presence of the silicon substrate on those masks where PS was previously present. The water contact angle of the composite polymer masks ranged from 70 to 90° which increased with the increase of PS vol% in the composite. The wetting behavior of certain PMMA masks showed hydrophobicity with water contact angle values above 90°.