Guest aggregation within poly(L-lactic acid)/pluronic P104 thin films

Rhodamine 6G (R6G) doped thin films composed of poly(L-lactic acid) (PLLA) and Pluronic P104 were spin cast onto glass microscope slides and characterized by ultraviolet-visible, steady-state, and time-resolved fluorescence spectroscopy. The results show that R6G aggregation within the film increases as the R6G concentration and P104 loading increases. These results suggest an approach for studying drug distributions (monomers, aggregates) within biodegradable polymer formulations.     

High-throughput characterization of film thickness in thin film materials libraries by digital holographic microscopy

A high-throughput characterization technique based on digital holography for mapping film thickness in thin-film materials libraries was developed. Digital holographic microscopy is used for fully automatic measurements of the thickness of patterned films with nanometer resolution. The method has several significant advantages over conventional stylus profilometry: it is contactless and fast, substrate bending is compensated, and the experimental setup is simple. Patterned films prepared by different combinatorial thin-film approaches were characterized to investigate and demonstrate this method. The results show that this technique is valuable for the quick, reliable and high-throughput determination of the film thickness distribution in combinatorial materials research. Importantly, it can also be applied to thin films that have been structured by shadow masking.     

High-throughput characterization of film thickness in thin film materials libraries by digital holographic microscopy

Abstract

A high-throughput characterization technique based on digital holography for mapping film thickness in thin-film materials libraries was developed. Digital holographic microscopy is used for fully automatic measurements of the thickness of patterned films with nanometer resolution. The method has several significant advantages over conventional stylus profilometry: it is contactless and fast, substrate bending is compensated, and the experimental setup is simple. Patterned films prepared by different combinatorial thin-film approaches were characterized to investigate and demonstrate this method. The results show that this technique is valuable for the quick, reliable and high-throughput determination of the film thickness distribution in combinatorial materials research. Importantly, it can also be applied to thin films that have been structured by shadow masking.     

Thermal conductivity imaging at micrometre-scale resolution for combinatorial studies of materials

Combinatorial methods offer an efficient approach for the development of new materials. Methods for generating combinatorial samples of materials, and methods for characterizing local composition and structure by electron microprobe analysis and electron-backscatter diffraction are relatively well developed. But a key component for combinatorial studies of materials is high-spatial-resolution measurements of the property of interest, for example, the magnetic, optical, electrical, mechanical or thermal properties of each phase, composition or processing condition. Advances in the experimental methods used for mapping these properties will have a significant impact on materials science and engineering. Here we show how time-domain thermoreflectance can be used to image the thermal conductivity of the cross-section of a Nb-Ti-Cr-Si diffusion multiple, and thereby demonstrate rapid and quantitative measurements of thermal transport properties for combinatorial studies of materials. The lateral spatial resolution of the technique is 3.4 microm, and the time required to measure a 100 x 100 pixel image is approximately 1 h. The thermal conductivity of TiCr(2) decreases by a factor of two in crossing from the near-stoichiometric side of the phase to the Ti-rich side; and the conductivity of (Ti,Nb)(3)Si shows a strong dependence on crystalline orientation.     

In vitro degradation and drug release from polymer blends based on poly(<Emphasis Type="SmallCaps">dl</Emphasis>-lactide), poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide-glycolide) and poly(ε-caprolactone)

Bioresorbable materials are extensively used for a wide range of biomedical applications. Accurately modifying and evaluating the degradation rate of these materials is critical to their performance and the controlled release of bioactive agents. The aim of this work was to modify the physical properties, degradation rate and drug delivery characteristics of thin films for medical applications by blending poly(dl-lactic acid) (PDLLA), poly(l-lactide-co-glycolide) (PLGA) and poly(ε-caprolactone) (PCL). The thin films were prepared using solvent casting and compression moulding and the in vitro degradation study was performed by immersing the films in a phosphate-buffered saline at elevated temperature for a period of 4 weeks. The degradation rate of the materials was analysed by differential scanning calorimetry, tensile testing and weight loss studies. The thermal analysis of the blends indicated that the presence of PLGA or PDLLA in the film resulted in increased degradation of the amorphous regions of PCL. It was observed that the samples consisting of PDLLA with PCL demonstrated the greatest weight loss. The decrease in mechanical properties observed for both sets of polymer blends proved to be similar. The solvent cast technique was selected as the most appropriate for the formation of the polymer/drug matrices, due to the potentially adverse thermal processing effects associated with compression moulding. It was found that modulation of drug release was achievable by altering the ratio of PCL to PDLLA or PLGA in the thin film blends.     

Combinatorial approaches as effective tools in the study of phase diagrams and composition-structure-property relationships

This article will provide an overview of state-of-the-art combinatorial/high-throughput methodologies and tools for accelerated materials research and discovery. Combinatorial thin films with discrete composition libraries or continuous composition gradients (spreads) have been widely used to study composition-structure-property relationships and to discover new functional materials. A diffusion-multiple approach—the creation of composition gradients and intermetallic phases by long-term annealing of junctions of three or more phases/alloys—enables effective studies of phase diagrams, kinetics, and composition-structure-property relationships of bulk alloys. Such studies are made possible by localized property measurements using micro-scale probes/measurement tools. Micro-scale probes for several properties such as elastic modulus, hardness, thermal conductivity, dielectric properties, optical properties, and crystal structures are relatively well developed and will be discussed in detail. The probes for electrical conductivity, magnetic properties, and compressive yield strength need further improvement or more benchmark studies. All these micro-scale probes are very useful for materials research. For instance, a micro-scale thermal conductivity probe can be used to study order-disorder transformation, site preference in intermetallic compounds, solid-solution effects on conductivity, and compositional point defect propensity. Several probes can be combined to accelerate the development of structural materials to obtain phase diagrams, diffusion coefficients, precipitation kinetics, solution-strengthening effects, and precipitation-strengthening effects. The probes yet to be developed that would have a significant impact on materials research include ones for lattice parameter measurements at micron-scale resolution, localized melting point measurements, ductility, thermal expansion coefficients, and thermodynamic properties. The impact of the development of the micro-scale probes goes beyond combinatorial materials research since most of them can be applied to non-combinatorial metallographic or thin film samples as well. Examples will show that in addition to improved efficiency, the systematic nature of the combinatorial approaches can reveal complex phenomena and interactions that otherwise would be difficult to be aware of or find using conventional one-composition-at-a-time practice, especially when measurements of several properties are made using multiple probes.     

Structures and properties of poly(3-alkylthiophene) thin-films fabricated though vapor-phase polymerization

Organic semiconducting polymer thin-films of 3-hexylthiophene, 3-octylthiophene, 3-decylthiophene, containing highly oriented crystal were fabricated by gas-phase polymerization using the CVD technique. These poly(3-alkylthiophene) films had a crystallinity up to 80%, and possessed a Hall mobility up to 10 cm2/Vs. The degree of crystalinity and the mobility values increased as the alkyl chain length increased. The crystal structure of the polymers was composed of stacked layers constructed by a side-by-side arrangement of alkyl chains and in-plane pi-pi stacking. These thin films are capable of being applied to organic electronics as the active materials used in thin-film transistors and organic photovoltaic cells.     

Dual DC magnetron cathode co-deposition of (Al,Ti) and (Al,Ti,N) thin films with controlled depth composition

In this work (Al,Ti) and (Al,Ti,N) films with composition gradient in depth starting either with pure Al or pure Ti were deposited on Si, glass and Au at room temperature in a DC magnetron discharge without bias. The plasma parameters, for both custom made cathodes, were determined and the process was real-time controlled to obtain in the plasma the necessary deposition changes in relative metal abundances to get the desired depth profile composition on the films. In this work the process was designed to get a constant gradient for the composition depth profile. The morphology of the films was analysed by SEM while the composition gradients were measured by SIMS, XPS and RBS, confirming preset nominal depth composition profile of the films.To obtain (Al,Ti,N) thin films with gradient depth composition, N₂ must be supplied to the discharges. The plasma behaviour is modified in the presence of N₂ and the influence on the film characteristics is studied using the same techniques referred above.The (Al,Ti) and (Al,Ti,N) film properties are compared. We succeed in validating the coating technique opening new application possibilities.     

Combinatorial initiated chemical vapor deposition (iCVD) for polymer thin film discovery

Initiated chemical vapor deposition (iCVD) is a technique used to synthesize polymer thin films and coatings from the vapor phase in situ on solid substrates via free-radical mechanisms. It is a solventless, low-temperature process capable of forming very thin conformal layers on complex architectures. By implementing a combinatorial approach that examines five initiation temperatures simultaneously, we have realized at least a five-fold increase in efficiency. The combinatorial films were compared to a series of blanket films deposited over the same conditions to ensure the combinatorial system provided the same information. Direct synthesis from the vapor phase allows for in situ control of film morphology, molecular weight and crosslinking, and the combinatorial system decreases the time required to find the relationship between these interrelated properties. Some coatings were tested for antimicrobial performance against E. coli and B. subtilis.     

酰基侧链对O-酰化壳寡糖/聚乳酸共混膜氢键的影响

以氯仿为共溶剂,用流延成膜法制备了不同酰基侧链O-酰化壳寡糖/聚乳酸（OCS/PLLA）共混膜,用FTIR、WAXD、DSC和TG等方法表征了共混膜中的氢键作用。结果表明,OCS/PLLA共混膜组分间存在较强的氢键相互作用,主要发生在O-酰化壳寡糖的氨基和聚乳酸的羰基之间;在保证脂溶性的前提下,酰基侧链越短,O-酰化壳...     

Pyroelectric polymer films

The objective of this investigation was to synthesize polymeric materials of high pyroelectric efficiency and to prepare thin test films suitable for use in pyroelectric vidicons.In our investigation of vinyl-addition polymers with highly polar pendant groups, we concentrated on atactic and isotactic substituted styrenes. Five atactic 4-substituted styrenes, poly(4-bromostyrene), poly(4-nitrostyrene), poly-(4-chlorostyrene), poly(4-methoxystyrene) and poly(4-fluorostyrene), were synthesized and evaluated, as were four isotactic 4-substituted styrenes, poly(4-bromostyrene), poly(4-chlorostyrene), poly(4-methoxystyrene) and poly(4-fluorostyrene).Hot-pressing was found to be a successful method of fabricating thick films of those polymers which did not undergo thermal decomposition near the melting point.Solvent casting of polymer films directly onto the test substrate proved to be the only practical method of handling brittle thin polymer films.Film formation by stretching and blowing was not found to be suitable for most of the polymers investigated.Laser evaporation was found to be a very useful technique for the preparation of polymer test films. Laser-evaporated poly(vinyl fluoride) showed the highest known pyroelectric coefficient for this material (1.8×10^-9C/cm² °K).None of the poly(4-substituted styrenes) showed any substantial pyro-electric behavior. This result can be attributed to their characteristics helical structure and lack of net permanent dipole moment.     

Sol–gel derived ZnO/PVP nanocomposite thin film for superoxide radical sensor

Pure ZnO films and ZnO nanoparticle-dispersed polyvinylpyrrolidone (PVP) composite films are prepared on Pyrex glass substrates by the sol–gel dip-coating technique utilizing zinc acetate precursor. The thin films are extensively characterized for surface morphology, chemistry, and nanocrystallite size using various advanced analytical techniques including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For the processing conditions considered, ZnO semiconductor thin films with nanocrystallite size 20–30 nm are obtained. The ZnO nanoparticle size in the PVP composite film increases with increase in ZnO content. The resistance of both the synthesized ZnO and ZnO/PVP thin films decrease significantly after exposure to solution containing superoxide anion radicals (SOR). The results thus indicate that ZnO and ZnO/PVP composite thin films can be used as biosensors for SOR and potentially for characterizing the antioxidant properties of fluids.     

Combinatorial optimization of a molecular glass photoresist system for electron beam lithography

Electron beam lithography is a powerful technique for the production of nanostructures but pattern quality depends on numerous interacting process variables. Orthogonal gradients of resist composition, baking temperatures, and development time as well as dose variations inside writing fields are used to prepare ternary combinatorial libraries for an efficient stepwise optimization of a molecular glass negative tone resist system.     

Tailoring molecular architectures with cobalt tetrasulfonated phthalocyanine: immobilization in layer-by-layer films and sensing applications

In the field of organic thin films, manipulation at the nanoscale can be obtained by immobilization of different materials on platforms designed to enhance a specific property via the layer-by-layer technique. In this paper we describe the fabrication of nanostructured films containing cobalt tetrasulfonated phthalocyanine (CoTsPc) obtained through the layer-by-layer architecture and assembled with linear poly(allylamine hydrochloride) (PAH) and poly(amidoamine) dendrimer (PAMAM) polyelectrolytes. Film growth was monitored by UV-vis spectroscopy following the Q band of CoTsPc and revealed a linear growth for both systems. Fourier transform infrared (FTIR) spectroscopy showed that the driving force keeping the structure of the films was achieved upon interactions of CoTsPc sulfonic groups with protonated amine groups present in the positive polyelectrolyte. A comprehensive SPR investigation on film growth reproduced the deposition process dynamically and provided an estimation of the thicknesses of the layers. Both FTIR and SPR techniques suggested a preferential orientation of the Pc ring parallel to the substrate. The electrical conductivity of the PAH films deposited on interdigitated electrodes was found to be very sensitive to water vapor. These results point to the development of a phthalocyanine-based humidity sensor obtained from a simple thin film deposition technique, whose ability to tailor molecular organization was crucial to achieve high sensitivity.     

Synthesis and characterization of thin films of poly(3-methyl thiophene) by rf-plasma polymerization

To facilitate synthesis of poly(3-methyl thiophene) thin film by RF-plasma polymerization process, suitable modifications have been done in a RF-sputtering set up. The deposition rate is found to be 3.33 nm/min. The synthesized films are characterized by FTIR, XRD, Ellipsometry, UV-Visible absorption spectroscopy and SEM. From FTIR, the formation of poly(3-methyl thiophene) has been confirmed. It is found that the synthesized polymer is cross-linked. XRD shows the amorphous nature of the prepared polymer film. The optical band gap has been estimated to be 2.14 eV from UV-visible absorption spectrum. Thickness of the polymer films has been measured to be 2000 Å by ellipsometry.     

Creation of biofunctionalized micropatterns on poly(methyl methacrylate) by single-step phase separation method

In this study, the polymer thin films containing micropatterns and biological functionalities were created by one-step procedure. The adjustable compositions among poly(methyl methacrylate) (PMMA), solvents, nonsolvent, and additional macromolecules formed the polymer thin films with different diameters ranging from 5 to 37 μm. The influences of topographical and chemical cues were investigated by directly cultivating L-929 fibroblasts on the prepared samples. The results revealed the predominant effect of surface topography that the cell density of L-929 fibroblasts increased proportionally with the average diameter of microconcaves. The cell number raised significantly on the PMMA thin films containing type I collagen and dopamine, with or without microstructures. On the other hand, the addition of bovine serum albumin in PMMA limited the growth of cells. The surface chemical composition and cell responses were evaluated by electron spectroscopy for chemical analysis (ESCA), viability assay, and immunostaining, respectively. This work proposed a simple and effective approach to incorporate the biological functions and surface topography simultaneously onto surface of materials that provided further applications for biomedical materials.     

Aragonite Nanorods in Calcium Carbonate/Polymer Hybrids Formed through Self‐Organization Processes from Amorphous Calcium Carbonate Solution

Nanostructured inorganic/polymer hybrid thin films comprising aragonite nanorods derived from aqueous suspensions of amorphous calcium carbonate (ACC) are prepared. For the formation of calcium carbonate (CaCO₃)/polymer hybrids, spincoated and annealed films of poly(vinyl alcohol) (PVA) that function as polymer matrices are soaked in aqueous colloidal solutions dispersing ACC stabilized by poly(acrylic acid) (PAA). In the initial stage, calcite thin films form on the surface. Subsequently, aragonite crystals start to form inside the PVA matrix that contains PVA crystallites which induce aragonite nucleation. Nanostructured hybrids composed of calcite thin films consisting of nanoparticles and assembled aragonite nanorods are formed in the matrices of PVA.     

Plasma polymers prepared by RF sputtering of polyethylene

Hydrocarbon plasma polymer thin films were deposited by means of magnetron sputtering of polyethylene (PE) using Ar as the working gas. AFM, ESCA, FTIR techniques were applied to investigate the films properties and composition. The films sputtered at Radio frequency (RF) power up to 100 W have a plasma polymer structure whereas further increase of RF power results in hydrocarbon plasma polymers more resembling conventional PE.     

Porous and dense poly(L-lactic acid) and poly(D,L-lactic acid-co-glycolic acid) scaffolds: <Emphasis Type="Italic">In vitro</Emphasis> degradation in culture medium and osteoblasts culture

The use of bioresorbable polymers as a support for culturing cells has received special attention as an alternative for the treatment of lesions and the loss of tissue. The aim of this work was to evaluate the degradation in cell culture medium of dense and porous scaffolds of poly(L-lactic acid) (PLLA) and poly(D,L-lactic acid-co-glycolic acid) (50:50) (PLGA₅₀) prepared by casting. The adhesion and morphology of osteoblast cells on the surface of these polymers was evaluated. Thermal analyses were done by differential scanning calorimetry and thermogravimetric analysis and cell morphology was assessed by scanning electron microscopy. Autocatalysis was observed in PLGA₅₀ samples because of the concentration of acid constituents in this material. Samples of PLLA showed no autocatalysis and hence no changes in their morphology, indicating that this polymer can be used as a structural support. Osteoblasts showed low adhesion to PLLA compared to PLGA₅₀. The cell morphology on the surface of these materials was highly dispersed, which indicated a good interaction of the cells with the polymer substrate.     

Molecular depth profiling of multilayer polymer films using time-of-flight secondary ion mass spectrometry

The low penetration depth and high sputter rates obtained using polyatomic primary ions have facilitated their use for the molecular depth profiling of some spin-cast polymer films by secondary ion mass spectrometry (SIMS). In this study, dual-beam time-of-flight (TOF) SIMS (sputter ion, 5 keV SF(5)(+); analysis ion, 10 keV Ar(+)) was used to depth profile spin-cast multilayers of poly(methyl methacrylate) (PMMA), poly(2-hydroxyethyl methacrylate) (PHEMA), and trifluoroacetic anhydride-derivatized poly(2-hydroxyethyl methacrylate) (TFAA-PHEMA) on silicon substrates. Characteristic positive and negative secondary ions were monitored as a function of depth using SF(5)(+) primary ion doses necessary to sputter through the polymer layer and uncover the silicon substrate (>5 x10(14) ions/cm(2)). The sputter rates of the polymers in the multilayers were typically less than for corresponding single-layer films, and the order of the polymers in the multilayer affected the sputter rates of the polymers. Multilayer samples with PHEMA as the outermost layer resulted in lowered sputter rates for the underlying polymer layer due to increased ion-induced damage accumulation rates in PHEMA. Additionally, the presence of a PMMA or PHEMA overlayer significantly decreased the sputter rate of TFAA-PHEMA underlayers due to ion-induced damage accumulation in the overlayer. Typical interface widths between adjacent polymer layers were 10-15 nm for bilayer films and increased with depth to approximately 35 nm for the trilayer films. The increase in interface width and observations using optical microscopy showed the formation of sputter-induced surface roughness during the depth profiles of the trilayer polymer films. This study shows that polyatomic primary ions can be used for the molecular depth profiling of some multilayer polymer films and presents new opportunities for the analysis of thin organic films using TOF-SIMS.