At The Dow Chemical Company, high-throughput research is an active area for developing new industrial coatings products. Using the principles of automation (i.e., using robotic instruments), parallel processing (i.e., prepare, process, and evaluate samples in parallel), and miniaturization (i.e., reduce sample size), high-throughput tools for synthesizing, formulating, and applying coating compositions have been developed at Dow. In addition, high-throughput workflows for measuring various coating properties, such as cure speed, hardness development, scratch resistance, impact toughness, resin compatibility, pot-life, surface defects, among others have also been developed in-house. These workflows correlate well with the traditional coatings tests, but they do not necessarily mimic those tests. The use of such high-throughput workflows in combination with smart experimental designs allows accelerated discovery and commercialization.

We describe the mechanism of cobalt and ligand binding on nanotextured poly(chloro-p-xylylene) (PPX) films as supports for catalytic release of H-2 from alkaline aqueous solutions of sodium borohydride. Cobalt catalysts are prepared on nanotextured PPX substrates via electroless plating using a Sn-free Pd(II) colloid with adsorbed pyridine ligand as an adhesion promoter. Gas physisorption studies on PPX, using N-2 and CO2 as probe gases, indicate the presence of micropores (similar to 1 to 2 nm width) responsible for the adsorption and non-covalent stabilization of pyridine molecules on the nanotextured surface. The strongly adsorbed pyridine molecules promote Co adhesion onto the PPX surface during subsequent electroless deposition, thereby retaining the metal's catalytic activity for H-2 evolution even after multiple reaction cycles. In contrast, conventionally deposited PPX is devoid of any nanotexture and contains fewer micropores capable of stabilizing pyridine adsorption, resulting in poor metallization and catalytic activity for H-2 evolution. We also demonstrate the effect of patterning the PPX substrate as a means to further improve the activity of the Co catalyst to achieve H-2 evolution rates comparable to those obtained using precious metal catalysts. (C) 2011 Elsevier B.V. All rights reserved.

The self-assembly of peptides, specifically dipeptides, offers numerous advantages for biological applications. We describe an easy, versatile method of fabricating different types of zwitterionic Phe-Phe dipeptide structures (i.e., tubes and vesicles) through solvent-mediated assembly. The stability of the dipeptide structures is increased by thin polymer coatings of poly(chloro-p-xylylene), a PPX film. We also investigated protein adsorption onto PPX-coated peptide tubes and vesicles by varying the thickness of the polymer film.

Parylene is an important class of polymer thin film that has wide-ranging applications due to its well-recognized properties, such as low-dielectric constant, biocompatibility, and exceptional barrier properties. Here, we studied the deposition of parylene nanofibers by template-based and template-free methods, which combine both vapor deposition polymerization and oblique angle deposition. A comparative study of two approaches based on surface characterization techniques is presented. These nanofibers, deposited by both approaches, have potential applications in catalysis, biodetection, and biomedical coatings.

Surface-enhanced Raman spectroscopy (SERS) substrates are prepared by electroless Ag metallization and vapor phase Au deposition on nanostructured poly(chloro-p-xylylene) (nanoPPX) templates. These substrates exhibit quasi-periodic nanomorphology inherited from the underlying nanoPPX template, resulting in highly reproducible SERS signal (<10% spot-to-spot and substrate-to-substrate signal variation for Au/nanoPPX comprising contributions from substrate imperfections). These substrates are therefore chosen for developing respiratory syncytial virus (RSV) gene detection that requires high sensitivity, stability, and reproducibility of the Raman signal. Metallized nanoPPX films show enhancement factors of similar to 10(4) to 10(6) that strongly depend on the metallization route and can be optimized by controlling the metallization parameters. RSV gene detection is achieved by using a molecular probe (MP) consisting of a fluorescent moiety and a thiol linker for attachment to the SERS substrate. To detect multiple targets, MPs are designed in two colors (Hex and Cy5 dyes) utilizing a broad range of fluorophores. Our approach provides reproducible dual-mode detection (i.e., fluorescent and SERS) where the assay results generated by fluorescence and SERS are self-confirmatory and eliminate false positives.

We describe a rapid, reliable method of preparing nanoporous Ni or Co films using nanostructured poly(chloro-p-xylylene) (nanoPPX) films as templates. The nanoPPX films are vapor deposited onto Si substrates using oblique angle polymerization (OAP), resulting in the formation of an obliquely aligned PPX nanorod array on the substrate. The nanoPPX films are then subjected to noncovalent functionalization using an aromatic ligand (i.e., pyridine) by means of treatment with either an aqueous solution of the ligand or ligand vapor. The results of quartz crystal microbalance and X-ray diffraction studies support a model in which pyridine adsorption is facilitated by the formation of pi-pi interactions with aromatic moieties in the amorphous surface regions of nanoPPX. The physisorbed pyridine in the nanoPPX film can subsequently bind a catalytic Pd(II)-based colloidal seed layer. Continuous, conformal Ni or Co films, characterized by FIB/SEM and AFM, are grown on the Pd(II)-laden nanoPPX films using electroless metallization. Analogous metallization of a conventionally deposited planar PPX film results in noncontinuous or patchy metal deposits. Such behavior is attributed to the sluggish adsorption of pyridine in the planar PPX film, resulting in an approximately 22-fold decrease in the quantity of pyridine adsorbed compared to that in a nanoPPX film. Consequently, the level of Pd(II) bound by pyridine on a planar PPX film is insufficient to catalyze continuous metallization. Results of a statistical two-level factorial design indicate that the morphology of the metal layer formed on a nanoPPX film is profoundly influenced by the ligand adsorption condition (i.e., aqueous ligand vs ligand vapor treatment) and is correlated to the catalytic activity of Co films for the production of hydrogen from sodium borohydride decomposition.

A highly accurate, real-time multisensor agent monitor for biomarker detection is required for early detection of kidney diseases. Urine creatinine level can provide useful information on the status of the kidney. We prepare nanostructured surface-enhanced Raman spectroscopy (SERS) substrates without template or lithography, which provides controllable, well-organized nanostructures on the surface, for the quantitative analysis of creatinine concentration in urine. We present our work on sensitivity of the SERS substrate to urine samples collected from diabetic patients and healthy persons. We report the preparation of a new type of SERS substrate, which provides fast (<10 s), highly sensitive (creatinine concentration <0.5 microg/mL) and reproducible (<5% variation) detection of urine. Our method to analyze the creatinine level in urine is in good agreement with the enzymatic method.

Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly( p -xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release droplet ratchet mechanism. Droplet retention forces in the pin and release directions differ by up to 80 μN, which is over ten times greater than the values reported for other engineered anisotropic surfaces. The nanofilm provides a microscale smooth surface on which to transport microlitre droplets, and is also relatively easy to synthesize by a bottom-up vapour-phase technique. An accompanying comprehensive model successfully describes the film’s anisotropic wetting behaviour as a function of measurable film morphology parameters.

The study of polymer-metal surfaces is important for basic scientific research as well as many practical applications in aircraft, automobile, biomedical, and electronics industries. The possibility of controlling particle size and particle surface chemistry of metals would help us to understand the fundamental mechanism of polymer-metal adhesion in general. We have recently demonstrated that nanostructured polymers can be fabricated by an oblique-angle polymerization method. These structures have a high aspect ratio and the production technique does not require any template or lithography method or a surfactant for deposition. We studied influences of the chemical functionality, morphology, and topology of the nanostructured films on the physical properties of metallic-polymer interfaces. Based on the nanostructured polymer mediated metal technology, we can develop novel polymer-metal interfaces with the following attributes: (1) high surface area materials with controlled roughness, (2) light weight and high adhesion strength of polymer to metal, and (3) industrial-scale deposition.

Abstract not Available.

We describe a simple, solution-based, two-step process for the fabrication of titania–parylene composite films as a prerequisite for their evaluation as materials for bioimplant applications. In the first step, a ligand capable of binding titania, such as phenylphosphonic acid, is physisorbed onto a nanostructured poly-p-xylylene thin film previously prepared via surface-promoted oblique angle polymerization of radicals formed during vapor-phase pyrolysis of [2.2]-p-cyclophanes. The adsorbed ligand templates conformal growth of titania on the polymer surface in the second step via a liquid phase deposition process involving the controlled hydrolysis of (NH4)2TiF6 in the presence of H3BO3 in pH 2.88 aqueous solution at ∼50 °C. SEM and AFM analyses support a deposition mechanism that includes direct growth of titania on the ligand-impregnated parylene surface, as well as incorporation of titania nanoparticles nucleated in solution into the growing film. XPS and XRD results show that the as-deposited titania contains both amorphous and nanocrystalline anatase phases, with the latter readily consolidated by annealing at ∼200 °C without destruction of the underlying parylene polymer. Titania adhesion can be tuned by proper choice of the ligand, with ligands such as phenylphosphonic acid that strongly bind to titanium dioxide leading to deposition of titania films that pass the Scotch® tape adhesion test.

Submitted for the MAR09 Meeting of The American Physical Society Spatially Organized Polymer Films Prepared by Oblique Angle Polymerization NIRANJAN MALVADKAR, MELIK DEMIREL, Pennsylvania State University — We developed a novel, bottom-up method to prepare nanostructured poly(p-xylylene) (PPX) films called oblique angle polymerization (OAP). In OAP, the monomer vapor flux is directed at an angle (< 10o) to the substrate. The morphology of the film is influenced by the combination of nucleation, surface diffusion and geometrical self-shadowing. The final nanostructure consists of 40 × 106 /mm2 obliquely aligned, quasi-periodic PPX nanowires on the substrate[1]. The nanostructure can be controlled by tuning the physical deposition parameters and/or the monomer chemistry. Functional materials prepared by depositing conformal metal layer on these nanostructured PPX films have opened new avenues of application in the areas of biodetection[2] and catalysis[3]. [1] Cetinkaya, M., Malvadkar, N., Demirel, M. J. Poly. Sci. B, 46, 640 (2008). [2] Kao, P., Malvadkar N., Wang, H., Allara, D., Demirel, M. Adv. Mat., 20, 3562 (2008). [3] Malvadkar, N., Park, S., MacDonald, M., Wang, H., Demirel, M. J. Power Sources, 182, 323 (2008). c ⃝ 2008 Elsevier Niranjan Malvadkar Pennsylvania State University Date submitted: 23 Nov 2008 Electronic form version 1.4

Nanostructured and planar films of poly(p-xylylene) (PPX) are fabricated by an oblique angle polymerization method and coated with cobalt using electroless deposition. The catalytic activity of cobalt coated on the nanostructured and planar PPX films is studied by measuring the rate of hydrogen evolution by the hydrolysis of alkaline-stabilized sodium borohydride (NaBH4) solution. The hydrogen release rate data show an asymptotic increase for the structured PPX film as a function of the electroless bath time, but the planar PPX films show a lower catalytic activity due to the inefficiency of cobalt deposition. The hydrogen release rate of the cobalt-coated nanostructured PPX film shows a rate between 2000 and 4250mL(gmin)−1 (i.e., rate of hydrogen gas per cobalt mass at room temperature and pressure), which is comparable to the values obtained on platinum, and ruthenium systems.

The development of a SERS substrate with high uniformity and sample-to-sample reproducibility is reported. Nanostructured poly(p-xylylene) films are prepared using an oblique-angle polymerization method, and SERS-active metals are deposited onto the nanostructured polymer by using thermal evaporation (see figure). The use of the substrate for a robust and reagentless detection of both Gram-positive and Gram-negative bacteria is demonstrated.

This study describes the evolution and growth of structured polymers by oblique angle deposition of poly(p-xylylene) (PPX) derivatives. The deposition of structured PPX polymers have been demonstrated recently, but the mechanism of growth has not been studied. Here, we provide experimental evidence for the growth of structured PPX polymers by an atomic force microscope, electron microscope, and a profilometer. Individual columns expand with respect to their heights according to a power-law, d = ch(P), where d is the column diameter, c and p are constants, and h is the height of a column. Values of p for structured poly(chloro-p-xylylene), poly(trifloroacetly-p-xylylene-co-p-xylylene), and poly(bromo-p-xylylene) films are estimated as 0.11 +/- 0.01, 0.15 +/- 0.01, and 0.18 +/- 0.01, respectively. This result is different from the traditional oblique angle deposition processes of nonpolymeric materials where the surface diffusion is low. Further analysis with two-dimensional power spectral density (PSD) method showed that the ordering of columns is quasi-periodic. Additionally, the X-ray and transmission electron microscope characterization of the columns revealed that the columns are semicrystalline. (C) 2008 Wiley Periodicals, Inc.