bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photopolymerization of Lyotropic Liquid Crystalline Systems: A New Route to Nanostructured Materials
Authors: Colson Colleen D. , Lester Christopher L. , Guymon C. Allan 
Published: April 2011

ABSTRACTIn recent years, a considerable amount of research has been dedicated to synthesizing highly ordered nanostructured materials. One way to achieve this is through templated polymerizations. A novel route to fabricating such materials is through the use of lyotropic liquid crystals (LLCs) that possess highly ordered nanostructures. However, LLC phases lack the necessary physical robustness. So, templating LLC phase morphology onto other materials such as organic polymers would give a nanostructure retained as part of a robust polymeric matrix. This study focuses on the photopolymerization behavior and structure retention of hydroxyethyl acrylate (HEA) / dodecyltrimethyl ammonium bromide (DTAB) / water system in a select LC phase. The results suggest that the polymerization behavior is heavily dependent on the type of LLC structure. Specifically, lamellar aggregates polymerize faster than either cubic or isotropic morphologies due to diffusional limitations on the growing polymer chain. Monomer segregation also plays a role in determining the polymerization rates. Results also indicate that the original LLC order of these systems is largely retained upon photopolymerization although some LLC phases do change upon cure. This order would be useful in applications such as ultrafiltration membranes, separation media, and drug delivery systems.
Polymer Dispersed Liquid Crystals as Mesoscale 2D and 3D Lattices
Authors: Escuti Michael J. , Crawford Gregory P. 
Published: April 2011

ABSTRACTWe introduce and explore two- and three-dimensional lattices formed in Holographic-Polymer Dispersed Liquid Crystals (H-PDLC) materials, which exhibit an electrically controllable index modulation in multiple dimensions. As electro-optically active holograms, these materials exhibit fast dynamic switching phenomena (~100 microseconds), and are simple to fabricate. While many applications have been proposed for these materials, almost all are based on one-dimensional index modulations in various grating regimes. However, constraints in additional dimensions lead to a much greater sensitivity of the polymer morphology to monomer functionality, exposure irradiance, and grating pitch. In an effort to begin to understand this relationship, two-dimensional triangle lattices were created using two monomeric blends exposed over a range of powers. Final diffraction efficiency (Bragg regime), saturation voltage, and polymer morphology were examined from the resulting triangle lattices. Three-dimensional lattices are discussed and a six-beam holographic method is proposed. Photonic crystal applications are envisioned where the pseudo-bandgap can be electrically controlled.
Structural Characterization of Segmented Polyurethanes by Small Angle Neutron Scattering
Authors: Espada Loren I. , Mang Joseph T. , Bruce Orler E. , Wrobleski Debra A. , Langlois David A. , Hjelm Rex P. 
Published: April 2011

ABSTRACTThe beneficial mechanical properties of segmented polyurethanes derive from microphase separation of immiscible hard and soft segment-rich domains at room temperature. We are interested in the structure of the domains, how these are affected by hydrolytic aging, and how the structure is modified by low molecular weight plasticizers. To assessed the distribution of the plasticizer in polyurethane, we did small-angle neutron scattering measurements on mixtures of 23% hard segment poly(esterurethane) with different amounts of either non-deuterated or deuterated plasticizer. We analyzed the results using a simple model in which the contrast, Δρ = ρH Š ρ, between the hard and soft segment-rich domains is varied by the amount of deuterated or hydrogenated plasticizer, using the fact that I(Q) ∼ Δρ2. The result demonstrated that the plasticizer is largely associated with the soft segment rich domains. The structure of PESU with the chain extender of the hard segment was assessed after aging under hydrolytic conditions. The results show that the microphase structure coarsens and segregates and that the hard and soft segments segregated as a result of the loss of constraints from hydrolytic soft segment chain scission. The results on plasticizer distribution and the effects of hydrolytic aging give insight on the loss of mechanical properties that occur in each case.
Polymerization of Poly(Itaconic Acid) on Surfaces by Atom Transfer Radical Polymerization in Aqueous Solution
Authors: Sankhe Amit Y. , Husson Scott M. , Kilbey S. Michael 
Published: April 2011

ABSTRACTPoly(itaconic acid) (PIA) was grown from surface-tethered initiator sites via atom transfer radical polymerization (ATRP). The surface-tethered PIA layers were grown from hydroxyl-terminated SAMs capped with initiator molecules of 4-(chloromethyl)-benzoylchloride. This polymerization initiator molecule and a copper-based organometallic catalyst allowed tethered PIA chains to be grown via ATRP at room temperature in aqueous solutions. Ellipsometric studies and external-reflection, Fourier-transform infrared spectroscopy (ER-FTIR) confirm the presence and growth of the surface-tethered PIA layer. We describe here how changing the temperature of polymerization alters the layer growth and kinetics of the process, and demonstrate, via ER-FTIR spectroscopy, that these surface-tethered layers do bind cationic dyes through ion-exchange mechanisms.
Mesophases of Regularly Branched Copolymers
Authors: Pickett Galen T. 
Published: April 2011

ABSTRACTThe phase diagram of A/B block copolymers is determined when the A block is a flexible, linear homopolymer, and the B block has a regularly branched tree structure with G generations. The predictions of a classical-path analysis and a lattice self-consistent mean field calculation are in general agreement. The phase diagram is considerably skewed toward keeping the A blocks inside cylindrical or spherical cores with the branched block forming a corona. There is little, if any, tendency for the branched arms to fold back to facilitate packing.
Stick-Slip Fracture of Polymer/Metal Interfaces
Authors: Toivola Y. , Somerday B.P. , Shediac R. , Ivill M.P. 
Published: April 2011

ABSTRACTThe adhesion of a thin-film of PMMA to substrates consisting of Ti or Al was measured using a four-point bend technique. Initial results revealed that cracks propagated along the PMMA/metal interfaces at stable rates. Subsequent experiments showed intermittent (“stick-slip”) interfacial crack propagation consisting of cycles of crack initiation, unstable propagation, and arrest. To investigate the origin of stick-slip fracture behavior at PMMA/metal interfaces the effect of water uptake by PMMA on fracture behavior was studied. Four-point bend sandwich specimens were stored in vacuum or deionized water environments at either 25 °C or 65 °C for a period of 7 days prior to testing. The PMMA/Al system stored at 25 °C showed a transition from stable to stick-slip crack propagation when the exposure environment was changed from vacuum to water. Interface crack propagation was stable for both the PMMA/Ti and PMMA/Al systems on exposure to 65 °C water, but the critical strain energy release rate, GC was markedly reduced, indicating that water uptake promoted stick-slip fracture up to some critical degree of hydration. No change in stick-slip behavior was observed from a variation in imposed load-point displacement rate.
Using Rheology to Probe the Mechanism of Joint Lubrication: Polyelectrolyte/protein interactions in Synovial Fluid
Authors: Oates Katherine M. N. , Krause Wendy E. , Colby Ralph H. 
Published: April 2011

ABSTRACTThe outstanding lubricating properties of synovial fluid, found in freely moving mammalian joints, may be due to intermolecular associations between hyaluronic acid, an anionic polysaccharide, and the plasma proteins. A synovial fluid model comprised of hyaluronic acid and the plasma proteins albumin and γ-globulins, was constructed. Rheological measurements reveal a pronounced viscoelasticity with a strong shear history dependence for the synovial fluid model and the plasma protein solutions at low shear rates. The addition of the anti-inflammatory drug D-Penicillamine to the solution alters the rheology of the synovial fluid model. We present two ideas about the structural features of synovial fluid that may explain this viscoelasticity and suggest further experimental techniques that can be used to test these ideas.
Assemblies of Polymerized Phospholipid Vesicle Structures Chemisorbed on Au Films Visualized in situ by Environmental Scanning Electron Microscopy
Authors: Stanish Ivan , Ray Richard I. , Singh Alok 
Published: April 2011

ABSTRACTSubmicron vesicles immobilized on gold films were visualized in situ using environmental scanning electron microscopy (ESEM). Electron micrographs show that surface immobilized vesicles composed of diacetylenic phospholipids with 1 mole percent disulfide functionality and that encapsulate NaCl are structurally stable for at least three days. Furthermore, energy dispersive spectroscopy (EDS) provides compositional evidence supporting the formation of surface immobilized vesicles. Using ESEM coupled with EDS, a two-layer vesicle structure was imaged and found to contain NaCl and lipid elements sulfur and phosphorous.
Porous Composites for Adhering Artificial Cartilage to Bone
Authors: Zhang Kai , Grimm Mary E. , Lu Qiwei , Oegema Theodore R. , Francis Lorraine F. 
Published: April 2011

ABSTRACTArtificial cartilage can be grown from cultured chondrocytes, but adhering this tissue to bone presents a challenge. Porous polymer/bioactive glass composites are candidate materials for engineering the artificial cartilage/bone interface and possibly other soft-to-hard tissue (ligament/bone, tendon/bone) interfaces. A phase separation technique was used to make porous polymer/bioactive glass composites. The composites (thickness: 200-500 μm) have asymmetric structures with dense top layers and porous structures beneath. The porous structures consist of large pores (>100 μm) in a network of smaller (<10 μm) interconnected pores. The dense layers were removed and large pores exposed by abrasion or salt leaching from the casting surface. The tissue bonding abilities of the composites were studied in vitro in simulated body fluid (SBF) and in rabbit chondrocyte culture. Culture studies revealed that composite surfaces were suitable for attachment, spreading and proliferation of chondrocytes. The growth of hydroxycarbonate apatite (HCA) inside and on the composites after soaking in the SBF for two weeks demonstrates their potential for integration with bone. The results indicate the potential for the composites to facilitate growth and attachment of artificial cartilage to bone.
Formation of Supramolecular Assemblies by Modulating Self-Assembling Properties of Diacetylenic Phosphocholines
Authors: Singh Alok , Wong Eva M. , Spector Mark S. , Schnur Joel M. 
Published: April 2011

ABSTRACTDiacetylenic phospholipid dispersions in water produce tubules (500 nm diameter) and helices from their initial vesicular morphology as a function of temperature and concentration. A binary mixture consisting of diacetylenic phospholipid, 1, 2 bis (tricosa-10, 12-diynoyl)-sn-glycero-3-phosphocholine and a short chain phospholipid, 1, 2-dinonanoyl -sn-glycero-3-phosphocholine was studied to explore the morphological transformation of lipids into tubules to develop an approach to control and produce tubules of different diameters. Circular dichroic spectra not only indicated the chiral nature of these tubules, but also provided distinct spectral signatures differentiating micro- and nanotubules. The effects of temperature and lipid concentration on the formation and stability of tubules were also explored. An equimolar lipid mixture provided structures with uniform morphology, which were stable for several hours up to 36 °C. The thermal stability of nanotubules makes them an attractive candidate for many practical applications including controlled release technology.
Immunoreactivity and Characterization of Histidine-Rich Peptide Encapsulated Nanoclusters
Authors: Slocik Joseph M. , Moore Joshua T. , Wright David W. 
Published: April 2011

ABSTRACTHistidine-rich proteins (HRP), which function in the biological control of inorganic materials, have been identified in the liver fluke Fasciola hepatica, marine polychaetes, humans, and the malarial parasite Plasmodium falciparum. For example, the malarial parasite contains HRP II composed of repeating peptide sequences of Ala-His-His-Ala-His-His-AlaAla-Asp. This peptide was screened as a stabilizing peptide coat for a variety of nanoclusters of Ag0, Au0, ZnS, TiO2, and Ag2S, and characterized by UV-Vis spectroscopy, fluorescence, IR, XRD, and TEM. The resulting nanoclusters were examined for immunoreactivity against a commercial monoclonal antibody for HRP II of P. falciparum.
Technical Studies on Renaissance Bronzes
Authors: Weisman Billie Milam , Reedy Chandra L. 
Published: April 2011

ABSTRACTThe merging of art production and technological innovation during the Renaissance in Europe led to some of the world's most renowned master works in bronze. Published technical studies of such bronzes are still relatively few in number. The objective of the present study was to conduct a comprehensive investigation of comparative examination and analysis on fifty-two bronze sculptures which were attributed to a wide variety of workshops and individual artists. The sculptures are housed in the permanent collection of the Kunsthistorisches Museum in Vienna, Austria, and were shown in the museum's 1987 exhibition, Renaissance Master Bronzes. Technical analysis included identifying and characterizing casting and fabricating techniques through visual surface examination; studying x-radiographs; and identifying clay core materials through thin-section petrography. The results of these studies were subsequently compared to technical treatises/accounts of bronze techniques by three Renaissance artist-scholars: Biringuccio (ca. 1540), Vasari (ca. 1550), and Cellini (ca. 1568). The present investigation shows a strong correlation between its technical results and those set forth by the above scholars from the Renaissance period. The findings of this research and comparison indicate that many methods and procedures in Renaissance bronze production were not standardized. Rather, there is shown to have been a wide range of technical variation. The broad variance is demonstrated through numerous processes, including: modes of separate cast-piece attachment, armature construction, chaplet insertion, selection of clay core and additive materials, and removal of clay core portions after casting. The variance is also evident in the quality and extent of surface tooling and/or chasing, and in the visual appearance of patinas. One result of this study is a better understanding of the nature of bronze sculpture technology during the Renaissance period.
Early Historic Period Ceramic Smoking Pipes from Budhigarh, in the Kalahandi District of Orissa, India
Authors: McCarthy Blythe , Downie Christine , Mohanty Pradeep 
Published: April 2011

ABSTRACTAmong ceramics found at early historic sites in the Kalahandi district of India are a great variety of terracotta smoking pipes or hukka. The pipes are fashioned from fine, iron-rich clay with extensive surface decoration. Their intricacy makes them the most distinctive art form of the area. Found at the majority of sites in the region, they are of special interest, both due to the care used in their execution and as they predate the introduction of tobacco to the area, leaving the plant being smoked a question. To determine their method of manufacture, and investigate the possibility of local manufacture, an initial study was conducted of a small number of pipes from the site of Budhigarh. The pipes, along with clay from the site (used extensively by modern potters), were studied using x-ray radiography, petrography, and inductively coupled plasma spectroscopy (ICP).
The Relationship Between Microstructure and Mechanical Properties of Late 19th/Early 20th Century Wrought Iron Using the Generalized Method of Cells Model
Authors: Hooper Jennifer J. , Graham Lori , Foecke Tim , Weihs Timothy P. 
Published: April 2011

ABSTRACTThe discovery of the RMS Titanic has led to a number of scientific studies, one of which addresses the role that the structural materials played in the sinking of the ship. Chemical, microstructural, and mechanical analysis of the hull steel suggests that it was state-of-the-art for 1912 with adequate fracture toughness for the application. However, the quality of the wrought iron rivets may have been an important factor in the opening of the steel plates during flooding. Preliminary studies of Titanic wrought iron rivets revealed an orthotropic, inhomogeneous composite material composed of glassy iron silicate (slag) particles embedded in a ferrite matrix. To date, very little is understood about the properties of wrought iron from that period. Therefore, in order to assess the quality of the Titanic material, contemporary wrought iron was obtained from additional late 19th/early 20th century buildings, bridges, and ships for comparison. Image analysis completed on the Titanic wrought iron microstructure showed a high slag content that is very coarse and unevenly distributed. To investigate how microstructure impacts the mechanical properties, and hence the quality of late 19th/early 20th century wrought iron, a detailed analysis of the relationship between the microstructural features and the mechanical behavior was completed. Here we present the first step in that process: the use of the Generalized Method of Cells (GMC) to predict the mechanical response of composites with variable microstructural properties. The GMC tool is used to generate the effective inelastic behavior of the composite from the individual constituent properties.
Analysis of CizhouMonochrome Green Enamels and Lead Glazes From Guantai Kiln in Northern China, Song to Jin Dynasty
Authors: Liu Wei , McCarthy Blythe 
Published: April 2011

ABSTRACTThe composition and microstructure of Cizhou monochrome overglaze enamels, the first known form of overglazed enamels in China, and green lead glazes from Guantai kiln were determined. Although microstructure and thickness of the enamels were very similar to those found for the single layer lead glazes, lead contents were lower. Enamels from the later part of the twelfth century formed a narrower compositional grouping than the lead glazes, indicating that increased control of the technology was attained. The monochrome enamels are thicker and have a composition distinct from that published for later painted enamels from sites other than Guantai. Increased viscosity and decreased values of thermal expansion coefficients were calculated for Guantai enamels relative to the glazes. An attempt to promote adhesion and reduce crawling may have caused the use of lower lead in the enamels relative to the single layer lead glazes.
Painted Qero Cups from the Inka and Colonial Periods in Peru: An Analytical Study of Pigments and Media
Authors: Newman Richard , Derrick Michele 
Published: April 2011

ABSTRACTQero cups, made from wood, ceramics and precious metals, have been used for millennia in the Andean region for ritual consumption of maize beer. From the cusp of the Inka-Colonial period, painted decoration became more common on qero cups. Most of the painted decoration actually consists of thin layers of a pigmented rubbery material that was cut and inlaid into shallow carved cavities in the wood substrate. For this project, 312 paint samples from 53 qerocups in collections of the Brooklyn Museum of Art, National Museum of the American Indian/Smithsonian Institution, Metropolitan Museum of Art, and American Museum of Natural History were analyzed. The study of paints is part of larger study of the technology of over 150 qero cups from these four collections. Samples from seven qeros in Peruvian collections have also been analyzed. Nearly two dozen pigments have been identified, including mineral, synthetic inorganic compounds, and natural dyestuffs. The binder consisted of an unusual natural resin (commonly called ‘mopa mopa’) usually mixed with a nondrying or semidrying oil. This resin, which was used at least locally during the pre-Inka period and continued to be used through the Colonial period and later, came from a tree that grows in the montana of southwest Colombia, a region that was part of the northernmost extension of the Inka empire.
High frequency contact mechanics based on quartz crystal resonators: application to polymer surfaces
Authors: Berg Steffen , Johannsmann Diethelm 
Published: April 2011

ABSTRACTHigh frequency contact mechanics experiments were carried with a quartz crystal resonator, the surface of which was coated with a polystyrene film. The experiment is based on the ring-down of the resonator after the electrical excitation has been stopped. When a tip touches the quartz surface, the shear motion of the quartz is perturbed, which can be used to study force-displacement and force-speed relations in the contact zone. A nonlinear spring constant κl(x) and a nonlinear friction coefficient ξl(ẋ) are explicitly derived. When a ceramic sphere touches a polymer film the friction force depends more than linearly on lateral speed. This contrasts to metal-metal contacts or contacts between ceramic surfaces, where the friction force depends either linearly of sub-linearly on speed.
Adhesion Property of Novel Polyimides Containing Fluorine and Phosphine Oxide Moieties
Authors: Jeong K. U. , Jo Y. J. , Knag H. M. , Yoon T. H. 
Published: April 2011

ABSTRACTNovel diamine monomers, containing fluorine and phosphine oxide - bis(3-aminophenyl)-3,5-bis(trifluoromethyl)phenyl phosphine oxide (mDA6FPPO) and bis(3-aminophenyl)-4-(trifluoromethyl)phenyl phosphine oxide (mDA3PPO) - were utilized to prepare polyimides with dianhydrides such as 6FDA, BTDA or ODPA by the conventional two-step route, i.e., preparation of poly(amic-acid), followed by solution imidization. Adhesion property of the polyimides was evaluated via a peel test with bare Cu foil, as well as Cr/silane coated Cu foils, and failure surfaces were analyzed by SEM/EDX to elucidate the adhesion mechanism. The polyimides with 3FDAm exhibited the highest Tg, followed by mDAPPO-, mDA3FPPO- and mDA6FPPO-based polyimides, but the mDAPPO-based polyimides exhibited the highest adhesion properties, followed by mDA3FPPO, mDA6FPPO, mDDS and 3FDAm, attributing to phosphine oxide and fluorine moieties.
Correlation Between Nanostructure and Crystalline Morphology and Mechanical Response in Nylon 6 Nanocomposites
Authors: Reynaud E. , Shah D. , Giannelis E.P. 
Published: April 2011

ABSTRACTSeveral nylon nanocomposites was prepared using pristine and organically modified silicates. DSC and XRD reveal that the metastable γ phase is stabilized in the nanocomposites and the amount of γ phase scales with the silicate loading. Both storage and loss moduli of the nanocomposites increase with increasing silicate content. The overall characteristics of these systems become more solid-like before the onset of the glass transition. The increases in moduli are most pronounced in the rubbery regime. Pristine silicates have marginal effect on the mechanical response due to poor dispersion and/or lack of interactions with the polymer matrix.