Showing papers by "Adam M. Rawlett published in 2007"

Super-Hydrophobic Surfaces via Micrometer-Scale Templated Pillars

Abstract: The fabrication of enhanced hydrophobic surfaces via simple and inexpensive means will be discussed. Regular arrays of microscale pores were prepared in polymer matrices via the spontaneous assembly of water-vapor condensation, the so-called breath figure method. Using these regular arrays of pores as templates, the analogous array of pillars (inverse pores) was transferred to polymeric films. These microtextured surfaces have greatly enhanced the hydrophobicity of the polymer when measured by the contact angle. This method of producing super-hydrophobic textured surfaces should be amenable to high-throughput, low-cost manufacturing of many polymeric surfaces.

Optical Properties of Phthalocyanine and Naphthalocyanine Compounds

Abstract: Phthalocyanines, naphthalocyanins, and their derivatives are frequently used as light modulating materials. These compounds, with their stable planar square structure and highly delocalized π-electron system, are being used in numerous technological applications, such as pigments in chemical sensors, and more recently as photosensitizers for photodynamic therapy. The nonlinear optical properties (NLO) of these compounds are of particular importance. Using density functional method (DFT), we calculated the optical properties of phthalocyanine and naphthalocyanine complexes with Si as a central atom. We examined the effect of hydrophilic axial substituents and the size of polycyclic aromatic hydrocarbons surrounding the porphyrazine-Si kernel on the optical properties of title molecules. Both UV-vis and RSA spectra are calculated and are compared with available experimental results. The time-dependent DFT (TDDFT) with the B3LYP functional predicts that the characteristic UV-vis absorption maxima are blue-shifted; however, the relative error is almost constant for phthalocyanine and naphthalocyanine compounds. The TDDFT triplet-triplet absorption spectra of Si-phthalocyanine and Si-naphthalocyanine complexes reproduce experimental data well.

Decontamination of Chemical Agent Simulant by Nanometal Oxides

Abstract: : The ability of a U.S. Army vehicle or a piece of equipment to decontaminate itself in situ from the threat of chemical agents is highly desirable and may reduce the weight and logistical footprints associated with decontamination operations. This work explores the ability of several nanometal oxide powders (that could potentially be incorporated into U.S. Army coatings) to decontaminate 2-chloroethyl ethyl sulfide, a simulant for the blister agent sulfur mustard. Another mustard stimulant, 2-chloroethyl phenyl sulfide, and a simulant for the nerve agent GB, dimethyl methylphosphonate, were also examined.

Nanoengineered Additives for Active Coatings

Abstract: : Novel additives for polymeric coatings have been developed based on modified hyperbranched polymers The additives are polyfunctional and have been prepared to spontaneously segregate to the surface of the polymer in which they are dispersed They ave been used to install active sites in polymeric films, with little or no change in the formulation, bulk properties, or application of the coating

Porous Thin Films Based on Photo-Cross-Linked

Abstract: Self-assembly processes and subsequent photo-cross-linking were used to generate cross-linked, ordered microporous structures on the surfaces of well defined four-arm star-shaped poly(D,L-lactide) (PDLLA) thin films. The four-arm star-shaped PDLLAs were synthesized using an ethoxylated pentaerythritol initiator. Solutions of the PDLLAs were cast in a humid environment, and upon solvent evaporation, ordered honeycomb structures (or breath figures) were obtained. Correlations between molar mass, polymer solution viscosity, and pore dimensions were established. The average pore dimension decreased with increasing polymer solution concentration, and a linear relationship was observed between relative humidity and average pore dimensions. Highly ordered microporous structures were also developed on four-arm star-shaped methacrylate-modified PDLLA (PDLLA-UM) thin films. Subsequent photo-cross-linking resulted in more stable PDLLA porous films. The photo-cross-linked films were insoluble, and the honeycomb structures were retained despite solvent exposure. Free-standing, structured PDLLA-UM thin films were obtained upon drying for 24 h. Ordered microporous films based on biocompatible and biodegradable polymers, such as PDLLA, offer potential applications in biosensing and biomedical applications.

Effect of Substituents on UV-Vis Spectra and RSA Properties of Phthalocyanine Compounds

Abstract: : The use of optically transparent materials to modulate or impede laser light in a real time setting is significant. This goal stimulates an interest in metalloporphyrins, phthalocyanines, naphthalocyanins and their derivatives. The most desired derivatives would be optically transparent, absorb laser light and also be soluble in water. Phthalocyanines (PC) with their stable, planar square structure and highly delocalized pi-electron system, are being used in numerous technological applications, such as pigments, in chemical sensors, and more recently as photosensitizers for photodynamic therapy. The nonlinear optical properties (NLO) of these compounds are of particular importance. Using quantum chemistry methods we study both visual and NLO properties of phthalocyanines complexes with Si as a central atom. The effect of hydrophilic axial substituents of the material on their optical properties is examined. We are mainly interested in the PEG poly(ethylene oxide) as an axial substituent because it is used in our laboratory to synthesize soluble PC complexes.