Search results for "Siloxane"
showing 10 items of 121 documents
Colloidal nanoparticle sorting and ordering on anodic alumina patterned surfaces using templated capillary force assembly
2017
Abstract A new, robust technique of size-selective nanoparticle ordering on porous anodized aluminum oxide (PAAO) templates is presented. Simultaneous particle sorting and array formation is achieved for the first time using a polydisperse suspension of irregularly shaped diamond nanocrystals. The array parameters can be tuned through a balance of evaporation driven particle flux, capillary, electrostatic, and adhesion forces, which are influenced by the asperities of the surface during the capillary and convective assembly dip-coating process. The resulting structures are dense (lower limit approximately 50 nm center separation), isolated (non-touching) nanoparticle arrays with a size dist…
Microstructuring of phospholipid bilayers on gold surfaces by micromolding in capillaries
2005
Microstructuring of lipid bilayers on gold surfaces was achieved by micromolding in capillaries employing chemically modified polydimethylsiloxane (PDMS). Microfluidic networks of PDMS were prepared by micromolding and functionalized with thiol end-groups using 3-mercaptopropyltrimethoxysilane. The PDMS stamps were firmly attached to the gold substrate via quasi-covalent linkage providing a tight seal, a prerequisite for establishing individual addressable capillaries. Bilayers composed of POPC/POPG were subsequently prepared on microstructured self assembly monolayers of 11-amino-1-undecanethiol via strong electrostatic interactions. This way it is possible to generate individually address…
Accelerated laboratory weathering of polypropylene composites filled with synthetic silicon-based compounds
2019
Abstract Non-functionalized and n-alkyl functionalized polyhedral oligomeric silsesquioxanes (POSS), siloxane-silsesquioxane resins and the sol-gel silicas were for the first time examined as possible UV-stabilizers and/or antioxidants in polypropylene (PP). The obtained composites were subjected to the accelerated laboratory weathering tests. The influence of the weathering conditions on the structure and properties of the PP materials was evaluated on the basis of the results from Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) studies. It was found that weathering resistance of the PP materials was strongly de…
The Unique Versatility of the Double Metal Cyanide (DMC) Catalyst: Introducing Siloxane Segments to Polypropylene Oxide by Ring-Opening Copolymerizat…
2020
The combination of hydrophobic polydimethylsiloxane (PDMS) blocks with hydrophilic polyether segments plays a key role for silicone surfactants. Capitalizing on the double metal cyanide (DMC) catalyst, the direct (i.e., statistical) copolymerization of cyclic siloxanes and epoxides is shown to be feasible. The solvent-free one-pot copolymerization of hexamethylcyclotrisiloxane and propylene oxide results in the formation of gradient propylene oxide (PPO)-PDMS copolymers. Copolymers with up to 46% siloxane content with low dispersities (Ð < 1.2) are obtained in the molecular weight range of 2100-2900 g mol-1 . The polymerization kinetics are investigated by pressure monitoring and in situ 1 …
High-resolution investigation of nanoparticle interaction with a model pulmonary surfactant monolayer.
2012
The pulmonary surfactant film spanning the inner alveolar surface prevents alveolar collapse during the end-exhalation and reduces the work of breathing. Nanoparticles (NPs) present in the atmosphere or nanocarriers targeted through the pulmonary route for medical purposes challenge this biological barrier. During interaction with or passage of NPs through the alveolar surfactant, the biophysical functioning of the film may be altered. However, experimental evidence showing detailed biophysical interaction of NPs with the pulmonary surfactant film are scant. In this study, we have investigated the impact of a hydrophobic polyorganosiloxane (AmOrSil20) NPs on the integrity as well as on the …
Microscopic observations of superficial ultrastructure of unworn siloxane-hydrogel contact lenses by cryo-scanning electron microscopy
2006
The purpose of this study was to analyze three commercial siloxane-hydrogel contact lens materials, lotrafilcon A, balafilcon A, and galyfilcon A, by cryogenic scanning electron microscopy (cryoSEM). The fully hydrated lenses were frozen in slush liquid nitrogen and qualitatively observed in a cryogenic scanning electron microscope. The superficial ultrastructure of the siloxane-hydrogels was observed at the areas where the lens fractured during sample cryogenic preparation. There are qualitative differences among the three examined materials in the complex polymer network structure existing between the outer layer and the underlying polymer. CryoSEM, although destructive, is a useful tool …
Microscopic observation of unworn siloxane-hydrogel soft contact lenses by atomic force microscopy
2006
In the present study, samples of lotrafilcon A, balafilcon A, and galyfilcon A contact lenses were observed by atomic force microscopy (AFM) in tapping mode at areas ranging from 0.25 to 400 m2. Mean roughness (Ra), root-mean-square roughness (Rms) and maximum roughness (Rmax) in nanometers were obtained for the three lens materials at different magnifications. The three contact lenses showed significantly different surface topography. However, roughness values were dependent of the surface area to be analyzed. For a 1 m2 area, statistics revealed a significantly more irregular surface of balafilcon A (Ra = 6.44 nm; Rms = 8.30 nm; Rmax = 96.82 nm) compared with lotrafilcon A (Ra = 2.40 nm; …
Long-term sealing ability of GuttaFlow versus Ah Plus using different obturation techniques.
2010
Objective. To compare the long-term sealing ability of GuttaFlow® using different obturation techniques. Study Design. Three hundred teeth, prepared with a crown-down technique, were divided into thirty experimental groups (n=10) to evaluate the apical and coronal leakage, at 3, 30 and 120 days, of lateral compaction gutta-percha + AH Plus?, lateral compaction gutta-percha + GuttaFlow®, single cone + AH Plus?, single cone + GuttaFlow®, and GuttaFlow® only. Results. Both coronal and apical leakage, at the three times of measurement, no significant differences were found among GuttaFlow® + lateral compaction gutta-percha and GuttaFlow® + single cone groups, whereas the only GuttaFlow® reached…
Small angle neutron scattering on periodically deformed polymers
1984
Small angle neutron scattering from periodically deformed samples is a useful extension of the methods presently available for the study of molecular dynamics of polymers. In this paper we describe apparatus that has been used to produce large cyclic deformations at frequencies upto 10 Hz and the principles by which data is collected to give spectra corresponding to different states of strain of the sample. Some data on model polydimethylsiloxane networks is given as an illustration of the value of this technique.
Ionic-liquid doped polymeric composite as passive colorimetric sensor for meat freshness as a use case.
2020
Abstract A composite membrane containing 1,2-naphthoquinone-4-sulfonic acid sodium salt (NQS) embedded in an ionic liquid (IL)- polydimethylsiloxane (PDMS)- tetraethyl orthosilicate (TEOS)- SiO2 nanoparticles (NPs) polymeric matrix is proposed. The selected IL was 1-methyl-3-octylimidazolium hexafluorophosphate (OMIM PF6). It is demonstrated that ILs chemical additives of PDMS influenced the sol-gel porosity. The sensor analytical performance for ammonia atmospheres has been tested as a function of sampling time (between 0.5 and 312 h), temperature (25 °C and 4 °C) and sampling volume (between 2L and 22 mL) by means of diffuse reflectance measurements and sensor photos, which can be registe…