| 1. |
- Aulin, Christian, et al.
(författare)
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Design of highly oleophobic cellulose surfaces from structured silicon templates
- 2009
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:11, s. 2443-2452
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Tidskriftsartikel (refereegranskat)abstract
- Structured silicon surfaces, possessing hierarchical porous characteristics consisting of micrometer-sized cavities superimposed upon a network of nanometer-sized pillars or wires, have been fabricated by a plasma-etching process. These surfaces have superoleophobic properties, after being coated with fluorinated organic trichlorosilanes, on intrinsically oleophilic surfaces. By comparison with flat silicon surfaces, which are oleophilic, it has been demonstrated that a combination of low surface energy and the structured features of the plasma-etched surface is essential to prevent oil from penetrating the surface cavities and thus induce the observed macroscopic superoleophobic phenomena with very low contact-angle hysteresis and low roll-off angles. The structured silicon surfaces were coated with cellulose nanocrystals using the polyelectrolyte multilayer technique. The cellulose surfaces prepared in this way were then coated with a monolayer of fluorinated trichlorosilanes. These porous cellulose films displayed highly nonwetting properties against a number of liquids with low surface tension, including alkanes such as hexadecane and decane. The wettability and chemical composition of the cellulose/silicon surfaces were characterized with contact-angle goniometry and X-ray photoelectron spectroscopy, respectively. The nano/microtexture features of the cellulose/silicon surfaces were also studied with field-emission scanning electron microscopy. The highly oleophobic structured cellulose surfaces are very interesting model surfaces for the development of biomimetic self-cleaning surfaces in a vast array of products, including green constructions, packaging materials, protection against environmental fouling, sports, and outdoor clothing, and microfluidic systems.
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| 2. |
- Burrows, Hugh D., et al.
(författare)
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Aqueous Solution Behavior of Anionic Fluorene-co-thiophene-Based Conjugated Polyelectrolytes
- 2009
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:4, s. 864-874
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Forskningsöversikt (refereegranskat)abstract
- Two anionic fluorene-thiophene alternating copolymers, poly[9,9-bis(4-sulfonylbutoxyphenyl)fluorene-2,7-diyl-2,5-thienylene] (PBS-PFT) and poly [9,9-bis(4-sulfonylbutoxyphenyl)fluorene-2,7-diyl-2,2'-bithiophene-5,5'- diyl] (PBS-PF2T), have been synthesized and their solution behaviors in water studied by UV-vis absorption spectroscopy, fluorescence, and electrical conductivity and compared with that of the previously studied conjugated polyelectrolyte (CPE) poly[9,9-bis(4-sulfonylbutoxyphenyl)fluorene-2,7-diyl-1,4-phenylene] (PBS-PFP). These conjugated polymers do not form solutions at the molecular level in water but instead form clusters. information on the structure of these clusters for PBS-PF2T comes from small-angle X-ray and neutron scattering. The relative ease of dispersing the copolymers in water increases with an increase in the number Of thiophene rings in these alternating copolymers. Semiempirical calculations on the structure suggest that this results from bending of the chains and increased conformational flexibility, decreasing interchain interactions. These CPEs can be dissolved in water at the molecular level using the nonionic surfactants n-dodecylpentaoxyethylene glycol ether (C12E5) or Triton X-100 to obtain systems with increased photoluminescence quantum yield and increased electrical conductivity that can be solution-processed for potential applications as components of sensory or optoelectronic devices.
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| 3. |
- Hansson, Susanne, et al.
(författare)
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ARGET ATRP for Versatile Grafting of Cellulose Using Various Monomers
- 2009
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:11, s. 2651-2659
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, cellulose-based materials have attracted significant attention. To broaden the application areas for cellulose, polymers are often grafted to/from the surface to modify its properties. This study applies ARGET (activators regenerated by electron transfer) ATRP (atom transfer radical polymerization) when straightforwardly grafting methyl methacrylate (MMA), styrene (St), and glycidyl methacrylate (GMA) from cellulose in the form of conventional filter paper In the presence of a sacrificial initiator. The free polymer, formed from the free initiator in parallel to the grafting, was characterized by H-1 NMR and SEC, showing that sufficient control is achieved. However, the analyses also indicated that the propagation from the surface cannot be neglected compared to the propagation of the free polymer at higher targeted molecular weights, which is an assumption often made. The grafted filter papers were evaluated with FT-IR, suggesting that the amount of polymer on the surface increased with increasing monomer conversion, which the FE-SEM micrographs of the substrates also demonstrated. Water contact angle (CA) measurements implied that covering layers of PMMA and PS were formed on the cellulose substrate, making the surface hydrophobic, in spite of low DPs. The CA of the PGMA-grafted filter papers revealed that, by utilizing either aprotic or protic solvents when washing the substrates, it was possible to either preserve or hydrolyze the epoxy groups. Independent of the solvent used, all grafted filter papers were essentially colorless after the washing procedure because of the low amount of copper required when performing ARGET ATRP. Nevertheless, surface modification of cellulose via ARGET ATRP truly facilitates the manufacturing since no thorough freeze-thaw degassing procedures are required.
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| 4. |
- Hulander, Mats, et al.
(författare)
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Blood interactions with noble metals: coagulation and immune complement activation.
- 2009
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Ingår i: ACS applied materials & interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:5, s. 1053-62
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Tidskriftsartikel (refereegranskat)abstract
- Noble metals are interesting biomaterials for a number of reasons, e.g., their chemical inertness and relative mechanical softness, silver's long known antimicrobial properties, and the low allergenic response shown by gold. Although important for the final outcome of biomaterials, little is reported about early events between pure noble metals and blood. In this article, we used whole blood in the "slide chamber model" to study the activation of the immune complement activation, generation of thrombin/antithrombin (TAT) complexes, and platelet depletion from blood upon contact with silver (Ag), palladium (Pd), gold (Au), titanium (Ti), and Bactiguard, a commercial nanostructured biomaterial coating comprised of Ag, Pd, and Au. The results show the highest TAT generation and platelet depletion on Ti and Au and lower on Pd, Ag, and the Bactiguard coating. The immune complement factor 3 fragment (C3a) was generated by the surfaces in the following order: Ag > Au > Pd > Bactiguard > Ti. Quartz crystal microbalance adsorption studies with human fibrinogen displayed the highest deposition to Ag and the lowest onto the Bactiguard coating. The adsorbed amounts of fibrinogen did not correlate with thrombogenicity in terms of TAT formation and platelet surface accumulation in blood. The combined results suggest, hence, that noble metal chemistry has a different impact on the protein adsorption properties and general blood compatibility. The low thrombogenic response by the Bactiguard coating cannot be explained by any of the single noble metal properties but is likely a successful combination of the nanostructure, nanogalvanic effects, or combinatory chemical and physical materials properties.
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| 5. |
- Johansson, Katarina, et al.
(författare)
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Hyperbranched Aliphatic Polyesters and Reactive Diluents in Thermally Cured Coil Coatings
- 2009
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:1, s. 211-217
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Tidskriftsartikel (refereegranskat)abstract
- Two hydroxy-functional hyperbranched aliphatic polyesters based on 2,2-dimethylolpropionic acid (bis-MPA) and a partially aromatic conventional polyester have been studied as thermoset resins for solvent-borne thermally cured polyester crosslinked with melamine coatings for precoated sheet metal, i.e., coil coatings. The hyperbranched polyesters differ with respect to the ratio of the end groups, being either hydroxyls or alkyl esters. The rheological properties of formulations with different polyester resin composition and reactive diluent, Le., rape seed methyl ester, content have been evaluated with viscosity measurements. Films cured either under industrial cure conditions to obtain a peak metal temperature of 232-241 degrees C or at a lower temperature, i.e., 130 degrees C, on untreated or organic primer-coated hot-dipped-galvanized steel substrates have been prepared. The film properties have been evaluated with differential scanning calorimetry and conventional film characterization techniques, i.e., adhesion, impact, Erichsen cupping, pencil hardness, microhardness, and scratch and chemical resistance tests. Formulations possessing high drying ability with maintained suitable film application viscosity were obtained using a hyperbranched polyester resin and a reactive diluent. It is proposed that a solvent-free polyester/melamine formulation with sufficient film properties to withstand the rough forming procedures associated with coil coatings can be obtained by further modification of the resin and greater amounts of reactive diluent.
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| 6. |
- Nordgren, Niklas, 1975-, et al.
(författare)
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Adhesion Dynamics for Cellulose Nano-Composites
- 2009
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Ingår i: ACS applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; , s. 2098-2103
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of poly(ε-caprolactone) (PCL) as a matrix polymer for cellulose nano-composites has been investigated at the macromolecular contact level using atomic force microscopy (AFM) in colloidal probe configuration. Model cellulose micro-spheres grafted with PCL were prepared via ring-opening polymerization (ROP). Force measurements between the functionalized particles revealed the adhesion to be highly dependent on contact time due to a diffusion controlled mechanism. Moreover, an increase of the temperature to 60 °C (close to Tm for the PCL-graft) greatly enhanced the adhesion at the polymer-polymer interface demonstrating the importance of entanglements in the annealing of composite materials.
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| 7. |
- Nyström, Daniel, et al.
(författare)
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Superhydrophobic and self-cleaning bio-fiber surfaces via ATRP and subsequent postfunctionalization
- 2009
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Ingår i: ACS applied materials & interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:4, s. 816-823
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Tidskriftsartikel (refereegranskat)abstract
- Superhydrophobic and self-cleaning cellulose surfaces have been obtained via surface-confined grafting of glycidyl methacrylate using atom transfer radical polymerization combined with postmodification reactions. Both linear and branched graft-on-graft architectures were used for the postmodification reactions to obtain highly hydrophobic bio-fiber surfaces by functionalization of the grafts with either poly(dimethylsiloxane), perfluorinated chains, or alkyl chains, respectively, Postfunctionalization using alkyl chains yielded results similar to those of surfaces modified by perfluorination, in terms of superhydrophobicity, self-cleaning properties, and the stability of these properties over time. in addition, highly oleophobic surfaces have been obtained when modification with perfluorinated chains was performed.
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| 8. |
- Pesen, Devrim, et al.
(författare)
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Modulation of Cell Adhesion Complexes by Surface Protein Patterns
- 2009
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:3, s. 543-548
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Tidskriftsartikel (refereegranskat)abstract
- Cell adhesion is an important process in several biological phenomena. To investigate the formation and organization of focal adhesions, we developed a patterning approach based on electron beam lithography. Nanodots (radius <1230 nm) and nanorings (inner radius <320 nm) of fibronectin (FN) were patterned on a K-Casein background. Intracellular vinculin immunofluorescence mirrored the FN nanopatterns. Atomic force microscopy showed that FN nanodots and nanorings organize the immediate cytoskeleton into straight fibrils and diverging fibril bundles, respectively. Our results suggest that a minimum of similar to 40 FN molecules is required for a cell to form a Focal adhesion.
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| 9. |
- Shah, Faiz Ullah, et al.
(författare)
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Synthesis, physicochemical, and tribological characterization of S-Di-n-octoxyboron-O,O'-di-n-octyldithiophosphate
- 2009
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:12, s. 2835-2842
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Tidskriftsartikel (refereegranskat)abstract
- Dialkyldithiophosphates (DTPs) of zinc(II), copper(II), and other metals have been extensively used as multifunctional additives in lubricants to control friction and reduce wear in mechanical systems. Among these DTP compounds, zinc dialkyldithiophosphates (ZnDTPs) are the most common additives extensively used for more than 60 years. These additives form a protective film on steel surfaces and, thus, control friction and reduce wear. However, ZnDTPs contain zinc and large amounts of phosphorus and sulfur, which impair the environment, both directly and indirectly, by adversely affecting the performance of catalytic converters of various automobiles. For this reason, environmental legislation imposes limitations on concentrations of phosphorus, sulfur, and zinc in the lubricants. In this work, we report on zinc-free S-di-n-octoxyboron-O,O′-di-n-octyldithiophosphate (DOB-DTP) lubricant additive with amount of phosphorus and sulfur reduced by half in a molecule as compared with ZnDTPs. DOB-DTP was synthesized by a reaction in two steps under inert nitrogen atmosphere. The final product, a viscous liquid, was characterized by the elemental analysis, FT-IR, multinuclear 1H, 13C, 31P, and 11B NMR spectroscopy and thermal analyses. Tribological performance of a mineral oil with this new additive was evaluated in comparison with O,O′-di-n-butyl-dithiophosphato-zinc(II) (ZnDTP) using a four-ball tribometer. The surface morphology and the elemental composition of the tribofilms were characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). The results show that DOB-DTP has a considerably better antiwear performance and higher stability of the coefficient of friction with time as compared with ZnDTP. Both phosphorus and sulfur were detected by the EDS on the worn steel surfaces at all concentrations of additives in the base oil.
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| 10. |
- Svensson, Anna, et al.
(författare)
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Surface Deposition and Phase Behavior of Oppositely Charged Polyion/Surfactant Ion Complexes. 1. Cationic Guar versus Cationic Hydroxyethylcellulose in Mixtures with Anionic Surfactants
- 2009
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:11, s. 2431-2442
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Tidskriftsartikel (refereegranskat)abstract
- Mixtures of cationic guar (cat-guar) or cationic hydroxyethylcellulose (cat-HEC) with the anionic surfactants sodium dodecyl sulfate or sodium lauryl ether-3 sulfate have been investigated by a wide range of complementary techniques (phase studies, turbidity measurements, dynamic light scattering, gel-swelling experiments, and in situ null ellipsometry), with the following objectives in mind: (1) to establish the relationship between the bulk phase behavior (precipitation and redissolution) of the polyion/surfactant ion complexes and formation/deposition Of such complexes at silica surfaces and (2) to obtain molecular interpretations of the large, previously unresolved, quantitative differences between the various investigated mixtures. There were clear similarities, for each studied system, between the bulk phase behavior, gel swelling, and surface deposition on increasing surfacant concentration. This is because all phenomena reflect the polyion/surfactant ion binding isotherm: an initial binding step at a low critical association concentration (cat) of the surfactant and a second more-or-less cooperative binding step beginning at a second cat, the cac(2). The details of the interactions are system-specific, however, and cat-guar/surfactant mixtures generally had larger precipitation regions and gave rise to larger adsorbed amounts on silica compared to mixtures with cat-HEC of a similar charge density. The observed quantitative differences are attributed to a difference in the hydrophobicity of the polyions. For cat-guar, the comparatively weak hydrophobic polyion/surfactant attraction is seen as a very gradual binding commencing at the cac(2) and continuing past the bulk l critical micelle concentration of the surfactant, resulting in an unusually large phase-separation region. For cat-HEC, the dissolution of the precipitate takes place at lower surfactant concentrations because of a stronger hydrophobic interaction between the surfactant and the polyion. The results have implications for the successful design of oppositely charged polyelectrolyte/surfactant formulations for surface deposition applications.
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