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PubMed Journals Articles About "Polymer Films Conduct Heat Instead Trapping" RSS

23:17 EDT 19th September 2019 | BioPortfolio

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Showing "Polymer Films Conduct Heat Instead Trapping" PubMed Articles 1–25 of 4,900+

Heating of Polymer Films Induced by High-Intensity Focused Ultrasound: Study of Acoustic and Thermal Effects.

This paper presents the study of the thermal and acoustic effects occurring in polymer samples of different thicknesses receiving high-intensity focused ultrasound (HIFU). Whereas the heating mechanisms in polymer plates immersed in water are well known, the physical mechanisms enabling the heating of polymer films using a solid waveguide transducer remain not fully understood. A coupled acousto-thermal finite element simulation is conducted to model the sound field and the heat generation inside polymer sa...


Tightly-Bound PMMA on Silica Has Reduced Heat Capacities.

The heat capacities of very small adsorbed amounts of poly(methyl methacrylate) on high surface-area silica (Cab-O-Sil) were measured using temperature-modulated differential scanning calorimetry (TMDSC) using a quasi-isothermal method and interpreted via different models. The composition-dependent heat capacities of the adsorbed samples were measurably less than those predicted with a simple mixture model. A two-state model, comprised of tightly- and loosely-bound polymer, fit the data better with heat cap...

Preparation and Composition Optimization of PEO:MC Polymer Blend Films to Enhance Electrical Conductivity.

The polymer blend technique was used to improve amorphous phases of a semicrystalline polymer. A series of solid polymer blend films based on polyethylene oxide (PEO) and methylcellulose (MC) were prepared using the solution cast technique. X-ray diffraction (XRD), Polarized optical microscope (POM), Fourier transform infrared (FTIR) and electrical impedance spectroscopy (EIS) were used to characterize the prepared blend films. The XRD and POM studies indicated that all polymer blend films are semicrystalli...


Hydrogen-bonded thin films of cellulose ethers and poly(acrylic acid).

Etherification of cellulose can get a series of water soluble derivatives, which can form hydrogen-bonded polymer complex with poly(acrylic acid) (PAA). Three cellulose ethers hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC) and methyl cellulose (MC) are LbL assembled with PAA to fabricate thin films. The hydrogen bonding of the films is characterized with FT-IR. The film growth behaviors are monitored by a quartz crystal microbalance (QCM) and a spectroscopic interferometer, which shows a differ...

The effect of the chemical composition and structure of polymer films made from resorbable polyhydroxyalkanoates on blood cell response.

Four PHA types were synthesized in the culture of Cupriavidus eutrophus B-10646 under special conditions, poly(3‑hydroxybutyrate) [P(3HB)] and of copolymers, which contained 3HB monomers and 4‑hydroxybutyrate (4HB), 3‑hydroxyvalerate (3HV), or 3‑hydroxyhexanoate (3HHx). All copolymers had the M of about 550-670 kDa, and the homopolymer P(3HB) had a significantly higher M - 920 kDa. P(3HB‑co‑4HB) and P(3HB‑co‑3HHx) had the lowest C (42 and 49%) while P(3HB‑co‑3HV) and P(3HB) exhibited...

Improved responsivity performance of ZnO film ultraviolet photodetectors by vertical arrays ZnO nanowires with light trapping effect.

The light trapping effect of ZnO UV PDs has been established as a promising way to optimize the performance of optoelectronic devices. In this paper, we report a light trapping fabricated metal-semiconductor-metal (MSM) structure, consisting of ZnO nanowire array as top layer light absorber supported by a ZnO film. The ZnO film is bridged between two interdigitated metal electrodes for collecting photo-generated carriers. In this connection, high-dense ZnO nanowires can be used as a light trapping unit and ...

Polymer Template Synthesis of Soft, Light, and Robust Oxide Ceramic Films.

Oxide ceramic materials underpin a wide variety of technologies. However, the inherent fragility of these materials limits their use in emerging fields like wearable electronics and soft energy storage devices. Here, we develop a sol-gel electrospinning technique followed by calcination to create a range of oxide ceramic nanofiber films that exhibit significant softness without fragility after various deformations. This approach causes the ceramic crystals to fuse together at a low temperature during their ...

Cu nanoparticles constrain segmental dynamics of cross-linked polyethers: a trade-off between non-fouling and antibacterial properties.

Copper has a strong bactericidal effect against multi-drug resistant pathogens and polyethers are known for their resistance to biofilm formation. Herein, we combined Cu nanoparticles (NPs) and a polyether plasma polymer in the form of nanocomposite thin films and studied whether both effects can be coupled. Cu NPs were produced by magnetron sputtering via the aggregation in a cool buffer gas whereas polyether layers were synthesized by Plasma-Assisted Vapor Phase Deposition with poly(ethylene oxide) (PEO) ...

Thermo- and Photo-Responsive Actuator with Free-standing Carbon Nitride Film.

The development of versatile actuators that convert environmental energy (heat or light, especially sunlight) into mechanical energy remains a great challenge. Herein, free-standing carbon nitride films were prepared by the physical vapor deposition method using bulk g-C3N4 powder as a starting material. The carbon nitride films exhibited controllable deformation under the stimuli of heat and light. An alarm device for high temperature and an artificial hand for grasping and releasing an object were designe...

CaCO mineralization in polymer composites with cellulose nanocrystals providing a chiral nematic mesomorphic structure.

CaCO mineralization was carried out using cellulose nanocrystal (CNC)/polymer composites wherein a chiral nematic structure of CNC assembly was immobilized in advance via a polymerization process of the precursory aqueous CNC/vinyl monomer lyotropics (7-11 wt% CNC in feed). Two series of polymer composites were prepared: CNC/poly(2-hydroxyethyl methacrylate) (PHEMA) and CNC/poly(2-hydroxyethyl methacrylate-co-acrylic acid) (P(HEMA-co-AA), HEMA:AA = 95:5-70:30 in mol). The mineralization was allowed to...

Combining Top-Down and Bottom-Up with Photodegradable Layer-by-Layer Films.

Layer-by-layer (LbL) self-assembly of polymer coatings is a bottom-up fabrication technique with broad applicability across a wide range of materials and applications that require control over interfacial properties. While most LbL coatings are chemically uniform in directions both tangent and perpendicular to their substrate, control over the properties of surface coatings as a function of space can enhance their function. To contribute to this rapidly advancing field, our group has focused on the top-down...

Characterization of Ultrathin Polymer Films Using p-polarized ATR-FTIR and Its Comparison with XPS.

We report on the chemical analysis of ultrathin (10 nm) polymer films using attenuated total reflectance (ATR)-FTIR technique based on p-polarized IR light and two types of enhancing substrates, i.e. metallic (Au) and dielectric (Si). We selected low temperature plasma treated ~ 10 nm-thick polystyrene films as a test case for demonstrating the capability of the p-polarized ATR-FTIR whose performance was further compared with the conventional X-ray photoelectron spectroscopy (XPS) techniques. Although the A...

A Predictive Transport Model for Convective Drying of Polymer Strip Films Loaded with a BCS Class II Drug.

Drying is an important unit operation in the manufacturing of polymer strip films as it affects various film quality attributes. Optimal design and control of convective drying process require models that capture the impact of critical process parameters such as air temperature and velocity on the temporal evolution of film thickness and moisture. Here, a detailed transport model was presented to capture moisture diffusion, heat transfer and moving boundary in convective drying of polymer strip films loaded...

Ultrafast, scalable laser photothermal synthesis and writing of uniformly dispersed metal nanoclusters in polymer films.

This paper presents a fast CO2 laser synthesis and writing technique - laser photothermal synthesis and writing (LPSW) - to generate and write a high concentration of unaggregated, spherical sub-10 nm metal nanoparticles (sMNPs). The method is generic, and we demonstrate the fabrication of Ni, Cu, and Ag directly in polymer thin films. A partly IR-absorbing thin polymer film can be heated by the laser to high temperatures in a short time, triggering metal-reduction, nucleation, and growth. Rapid quenching o...

Development of mucoadhesive vaginal films based on HPMC and zein as novel formulations to prevent sexual transmission of HIV.

Although vaginal films were initially developed for a fast release of the drug, with the adequate formulation they can also be useful for sustained release. The latest strategies for the prevention of the sexual transmission of HIV have moved towards sustained-release dosage forms, so films may be an effective strategy that could also improve the patient's comfort. A hydrophilic polymer (hydroxypropylmethyl cellulose) and an amphiphilic polymer (zein) have been evaluated for the development of Tenofovir sus...

Microcrystalline array structures induced by heat treatment of friction-transferred organic semiconductor films.

The correlation between molecular orientation and optoelectrical properties is most critical to the future design of molecular materials. We made highly-anisotropic microcrystalline array structures with an organic semiconductor, a methoxy-substituted thiophene/phenylene co-oligomer (TPCO), by depositing it on friction-transferred poly(tetrafluoroethylene) (PTFE) layers fabricated on substrates with several heat treatments. Polarising microscope observation, polarised emission and absorption spectra measure...

Improvement of Sensing Performance of Impedancemetric C₂H₂ Sensor Using SmFeO₃ Thin-Films Prepared by a Polymer Precursor Method.

A sensitive an impedancemetric acetylene (C₂H₂) gas sensor device could be fabricated by using perovskite-type SmFeO₃ thin-film as a sensor material. The uniform SmFeO₃ thin-films were prepared by spin-coating and focusing on the effects of polymer precursor solutions. The prepared precursors and thin-films were characterized by means of thermal analysis, Fourier-transform infrared spectroscopy, ultraviolet⁻visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy and X-ray ph...

Universal Route to Impart Orthogonality to Polymer Semiconductors for Sub-Micrometer Tandem Electronics.

A universal method that enables utilization of conventional photolithography for processing a variety of polymer semiconductors is developed. The method relies on imparting chemical and physical orthogonality to a polymer film via formation of a semi-interpenetrating diphasic polymer network with a bridged polysilsesquioxane structure, which is termed an orthogonal polymer semiconductor gel. The synthesized gel films remain tolerant to various chemical and physical etching processes involved in photolithogr...

Thermoplastic Polyurethane Elastomer-Based Gel Polymer Electrolytes for Sodium Metal Cells with Enhanced Cycling Performance.

Sodium batteries have been recognized as a promising alternative to lithium-ion batteries. However, the liquid electrolyte used in these batteries has inherent safety problems. Polymer electrolyte has been considered as a safer and more reliable electrolyte system for rechargeable batteries. Herein, we report a thermoplastic polyurethane elastomer-based gel polymer electrolyte with high ionic conductivity and high elasticity. It has an ambient temperature ionic conductivity of 1.5 mS cm-1 and high stretchab...

Enhanced Hole Transport in Ternary Blend Polymer Solar Cells.

Recently, ternary blend polymer solar cells have attracted great attention to improve a short-circuit current density (Jsc) effectively because complementary absorption bands can harvest the solar light over a wide wavelength range from visible to near-IR region. Interestingly, some ternary blend solar cells have shown improvements not only in Jsc but also in a fill factor (FF). Previously, we also reported that a ternary blend solar cell based on a low-bandgap polymer PTB7-Th, a wide-bandgap polymer PDCBT,...

Functionalized Cellulose Nanocrystal-Mediated Conjugated Polymer Aggregation.

Inducing the self-assembly of π-conjugated polymers into semicrystalline aggregates has been a topic of substantial interest in the field of organic electronics and is typically achieved using energy-intensive solution processing or postfilm deposition methods. Here, we demonstrate the ability of bioderived cellulose nanocrystals (CNCs) to act as structure-directing agents for the conjugated semiconducting polymer, poly(3-hexylthiophene) (P3HT). CNCs were grafted with polystyrene, P3HT or poly( N-isopropyl...

Water vapor sorption-desorption hysteresis in glassy surface films of mucins investigated by humidity scanning QCM-D.

Investigating the origin of water sorption-desorption hysteresis in glassy biopolymers is important for understanding the properties of biological barriers, such as the mucus epithelium. In general, hysteresis is a result of a complex interplay between diffusion of water and relaxation of the polymer matrix. Our hypothesis is that for thin films, typical for quartz crystal microbalance with dissipation monitoring (QCM-D) experiments performed in gas phase with defined relative humidity, the diffusion limita...

Film formation of high latex using hydroplasticization: Explanations from NMR relaxometry.

The film formation of acrylic latex dispersions, containing different amounts of carboxylic acid functional groups by the incorporation of methacrylic acid (MAA), was studied with GARField H NMR at various relative humidities (). Polymer particles with glass transition temperatures in the range from 26 to 50 °C formed films at room temperature, because of hydroplasticization. It was found that with increased drying rate due to lower , the evaporation flux of water was limited by the latex polymer. Only in ...

Real time MRI to elucidate the functionality of coating films intended for modified release.

Polymer films based on mixtures of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) have been widely used to coat pellets and tablets to modify the release profile of drugs. For three different EC/HPC films we used H and F MRI in combination with a designed release cell in real time to record the drug, polymer and water in 5 dimensional (5D) datasets; three spatial, one diffusion or relaxation and a temporal dimension. We observed that the water inflow through the films correlated with the initiation ...

Effect of fibrous TiO filler on the structural, mechanical, barrier and optical characteristics of biodegradable maize starch/PVA composite films.

The work focuses on producing and evaluating "green" multifunctional film materials based on a mixed eco-friendly starch/PVA matrix and filled with fibrous TiO particles formed by the ultrasound-assisted biotemplate method. Starch/PVA/TiO film-forming dispersions were prepared by heating and intensively mixing the components at the same time, and then composite films were obtained by the casting method. The influence of the TiO filler content on the morphological and structural characteristics of the compos...


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