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Polymeric Substrates (polymeric + substrate)
Selected AbstractsAtmospheric Pressure Barrier Discharge Deposition of Silica-Like Films on Polymeric SubstratesPLASMA PROCESSES AND POLYMERS, Issue S1 2007Sergei Starostine Abstract Silica-like coatings were deposited on polymer foils in APG discharge in a roll-to-roll configuration. The dependence of film structure and chemical composition on the conditions during deposition process was studied by means of SEM, ATR-FTIR, and XPS analysis. The influence of oxidant concentration on the deposited film properties is analyzed and discussed. It was observed that pulsing of the APG discharge suppresses dust formation in atmospheric plasma and, therefore, provides uniform coatings. [source] Assembled structures of nanocrystals in polymer/calcium carbonate thin-film composites formed by the cooperation of chitosan and poly(aspartate)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Ayae Sugawara Abstract Assembled structures of calcium carbonate (CaCO3) nanocrystals have been examined for polymer/CaCO3 thin-film composites synthesized through a self-organization process inspired by biomineralization. For the crystallization of CaCO3, a thin-film matrix of chitosan has been used as a polymeric substrate. When the matrix is immersed into a supersaturated aqueous solution of CaCO3 containing 1.4 × 10,3 wt % poly(aspartate) (PAsp), thin-film crystals of CaCO3 are formed spontaneously. Three kinds of disklike films have been observed under a polarizing optical microscope. Electron diffraction analyses of each film have revealed that one is aragonite, displaying radial orientation of the c axes, and the others are vaterite, exhibiting different orientations. Detailed observation by scanning electron microscopy has clarified that these films are assemblies of crystalline particles 10,20 nm in size. The thin-film composites have been obtained over a PAsp concentration range of 4.4 × 10,4 to 1.0 × 10,2 wt %. Vaterite formation becomes dominant when the concentration of PAsp is increased. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5153,5160, 2006 [source] A structural basis for processivityPROTEIN SCIENCE, Issue 9 2001Wendy A. Breyer Abstract The structures of a number of processive enzymes have been determined recently. These proteins remain attached to their polymeric substrates and may perform thousands of rounds of catalysis before dissociating. Based on the degree of enclosure of the substrate, the structures fall into two broad categories. In one group, the substrate is partially enclosed, while in the other class, enclosure is complete. In the latter case, enclosure is achieved by way of an asymmetric structure for some enzymes while others use a symmetrical toroid. In those cases where the protein completely encloses its polymeric substrate, the two are topologically linked and an immediate explanation for processivity is provided. In cases where there is only partial enclosure, the structural basis for processivity is less obvious. There are, for example, pairs of proteins that have quite similar structures but differ substantially in their processivity. It does appear, however, that the enzymes that are processive tend to be those that more completely enclose their substrates. In general terms, proteins that do not use topological restraint appear to achieve processivity by using a large interaction surface. This allows the enzyme to bind with moderate affinity at a multitude of adjacent sites distributed along its polymeric substrate. At the same time, the use of a large interaction surface minimizes the possibility that the enzyme might bind at a small number of sites with much higher affinity, which would interfere with sliding. Proteins that can both slide along a polymeric substrate, and, as well, recognize highly specific sites (e.g., some site-specific DNA-binding proteins) appear to undergo a conformational change between the cognate and noncognate-binding modes. [source] Template-Guided Self-Assembly of Colloidal Quantum Dots Using Plasma LithographyADVANCED MATERIALS, Issue 12 2009Michael Junkin A plasma lithography technique is developed to guide the self-assembly of colloidal quantum dots and other nanoscale building blocks, including fluorescent nanoparticles, gold nanoparticles, salts, and proteins. Plasma lithography enables the self-assembly of nanoscale materials onto soft and polymeric substrates with feature sizes as small as 100,nm. [source] Simple Fabrication Method of Conductive Polymeric Arrays by Using Direct Laser Interference Micro-/Nanopatterning,ADVANCED MATERIALS, Issue 9 2007A. Acevedo Thin films of polyaniline (PANI) deposited onto different polymeric substrates are nanostructured by using "direct laser interference patterning" at room temperature and pressure in air atmosphere. Regular linelike arrays (see figure) with thicknesses up to 600,nm are fabricated and their activity is determined using different techniques. The structuring mechanisms of PANI supported in both polycarbonate and polyimide films are demonstrated using cross-sectional analyses performed with a dual-beam workstation. [source] Photografting of acrylic acid and methacrylic acid onto polyolefines initiated by formaldehyde in aqueous solutionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2009Jianmei Han Abstract Formaldehyde aqueous solution can act as an effective photoinitiating system for water-borne photografting. The photografting of acrylic acid (AA) and methacrylic acid (MAA) onto high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polypropylene (PP) initiated by formaldehyde aqueous solutions has been reported. The effects of formaldehyde content and monomer concentration on grafting varied with the polymeric substrates and monomers used. For the grafting of AA onto HDPE, the extent of grafting increased with increasing formaldehyde content in the solution, monomer concentration had a little effect on grafting. Whereas for the grafting of MAA onto HDPE, the grafting performed in 8% formaldehyde aqueous solution lead to the highest extent of grafting, the extent of grafting increased with monomer concentration till 2.5 mol/L. MAA was easier to be grafted onto the polyolefins than AA. The easiness of grafting occurring on the polyolefins was in a decreasing order of LDPE > HDPE > PP. Qualitative and semi-quantitative Fourier transform infrared (FTIR) characterizations of the grafted samples were performed. For both grafted LDPE and PP samples, at the same irradiation time, the carbonyl index of the samples grafted with MAA was higher than that grafted with AA. The FTIR results are in accord with the results obtained by gravimetric method. The water absorbency of the grafted samples increased almost linearly with the extent of grafting. The PE films grafted with AA adsorbed more water than those grafted with MAA. This study had broadened the water-borne initiating system for photografting. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Role of substrate material in failure of crown-like layer structures,JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2007Jae-Won Kim Abstract The role of substrate modulus on critical loads to initiate and propagate radial cracks to failure in curved brittle glass shells on compliant polymeric substrates is investigated. Flat glass disks are used to drive the crack system. This configuration is representative of dental crown structures on dentin support in occlusal contact. Specimens are fabricated by truncating glass tubes and filling with epoxy-based substrate materials, with or without alumina filler for modulus control. Moduli ranging from 3 to 15 GPa are produced in this way. Critical loads for both initiation and propagation to failure increase monotonically with substrate modulus, by a factor of two over the data range. Fracture mechanics relations provide a fit to the data, within the scatter bands. Finite element analysis is used to determine stress distributions pertinent to the observed fracture modes. It is suggested that stiffer substrate materials offer potential for improved crown lifetime in dental practice. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Integrated surface modification of fully polymeric microfluidic devices using living radical photopolymerization chemistryJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Robert P. Sebra Abstract Surface modification using living radical polymerization (LRP) chemistry is a powerful technique for surface modification of polymeric substrates. This research demonstrates the ability to use LRP as a polymer substrate surface-modification platform for covalently grafting polymer chains in a spatially and temporally controlled fashion. Specifically, dithiocarbamate functionalities are introduced onto polymer surfaces using tetraethylthiuram disulfide. This technique enables integration of LRP-based grafting for the development of an integrated, covalent surface-modification method for microfluidic device construction. The unique photolithographic method enables construction of devices that are not substrate-limited. To demonstrate the utility of this approach, both controlled fluid flow and cell patterning applications were demonstrated upon modification with various chemical functionalities. Specifically, poly(ethylene glycol) (375) monoacrylate and trifluoroethyl acrylate were grafted to control fluidic flow on a microfluidic device. Before patterning, surface-functionalized samples were characterized with both goniometric and infrared spectroscopy to ensure that photografting was occurring through pendant dithiocarbamate functionalities. Near-infrared results demonstrated conversion of grafted monomers when dithiocarbamate-functionalized surfaces were used, as compared to dormant control surfaces. Furthermore, attenuated total reflectance/infrared spectroscopy results verified the presence of dithiocarbamate functionalities on the substrate surfaces, which were useful in grafting chains of various functionalities whose contact angles ranged from 7 to 86°. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1404,1413, 2006 [source] A structural basis for processivityPROTEIN SCIENCE, Issue 9 2001Wendy A. Breyer Abstract The structures of a number of processive enzymes have been determined recently. These proteins remain attached to their polymeric substrates and may perform thousands of rounds of catalysis before dissociating. Based on the degree of enclosure of the substrate, the structures fall into two broad categories. In one group, the substrate is partially enclosed, while in the other class, enclosure is complete. In the latter case, enclosure is achieved by way of an asymmetric structure for some enzymes while others use a symmetrical toroid. In those cases where the protein completely encloses its polymeric substrate, the two are topologically linked and an immediate explanation for processivity is provided. In cases where there is only partial enclosure, the structural basis for processivity is less obvious. There are, for example, pairs of proteins that have quite similar structures but differ substantially in their processivity. It does appear, however, that the enzymes that are processive tend to be those that more completely enclose their substrates. In general terms, proteins that do not use topological restraint appear to achieve processivity by using a large interaction surface. This allows the enzyme to bind with moderate affinity at a multitude of adjacent sites distributed along its polymeric substrate. At the same time, the use of a large interaction surface minimizes the possibility that the enzyme might bind at a small number of sites with much higher affinity, which would interfere with sliding. Proteins that can both slide along a polymeric substrate, and, as well, recognize highly specific sites (e.g., some site-specific DNA-binding proteins) appear to undergo a conformational change between the cognate and noncognate-binding modes. [source] Cloning, expression, and characterization of novel thermostable family 7 cellobiohydrolasesBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008Sanni P. Voutilainen Abstract As part of the effort to find better cellulases for bioethanol production processes, we were looking for novel GH-7 family cellobiohydrolases, which would be particularly active on insoluble polymeric substrates and participate in the rate-limiting step in the hydrolysis of cellulose. The enzymatic properties were studied and are reported here for family 7 cellobiohydrolases from the thermophilic fungi Acremonium thermophilum, Thermoascus aurantiacus, and Chaetomium thermophilum. The Trichoderma reesei Cel7A enzyme was used as a reference in the experiments. As the native T. aurantiacus Cel7A has no carbohydrate-binding module (CBM), recombinant proteins having the CBM from either the C. thermophilum Cel7A or the T. reesei Cel7A were also constructed. All these novel acidic cellobiohydrolases were more thermostable (by 4,10°C) and more active (two- to fourfold) in hydrolysis of microcrystalline cellulose (Avicel) at 45°C than T. reesei Cel7A. The C. thermophilum Cel7A showed the highest specific activity and temperature optimum when measured on soluble substrates. The most effective enzyme for Avicel hydrolysis at 70°C, however, was the 2-module version of the T. aurantiacus Cel7A, which was also relatively weakly inhibited by cellobiose. These results are discussed from the structural point of view based on the three-dimensional homology models of these enzymes. Biotechnol. Bioeng. 2008;101: 515,528. © 2008 Wiley Periodicals, Inc. [source] | ||||||||||