Results 1 - 10 of 3365
Results 1 - 10 of 3365. Search took: 0.026 seconds
|Sort by: date | relevance|
[en] The macroporous synthetic poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels as 3D cellular scaffolds with specific internal morphology, so called dual pore size, were designed and studied. The morphological microstructure of hydrogels was characterized in the gel swollen state and the susceptibility of gels for stem cells was evaluated. The effect of specific chemical groups covalently bound in the hydrogel network by copolymerization on cell adhesion and growth, followed by effect of laminin coating were investigated. The evaluated gels contained either carboxyl groups of the methacrylic acid or quaternary ammonium groups brought by polymerizable ammonium salt or their combinations. The morphology of swollen gel was visualized using the laser scanning confocal microscopy. All hydrogels had very similar porous structures – their matrices contained large pores (up to 102 μm) surrounded with gel walls with small pores (100 μm). The total pore volume in hydrogels swollen in buffer solution ranged between 69 and 86 vol%. Prior to the seeding of the mouse embryonal stem cells, the gels were coated with laminin. The hydrogel with quaternary ammonium groups (with or without laminin) stimulated the cell growth the most. The laminin coating lead to a significant and quaternary ammonium groups. The gel chemical modification influenced also the topology of cell coverage that ranged from individual cell clusters to well dispersed multi cellular structures. Findings in this study point out the laser scanning confocal microscopy as an irreplaceable method for a precise and quick assessment of the hydrogel morphology. In addition, these findings help to optimize the chemical composition of the hydrogel scaffold through the combination of chemical and biological factors leading to intensive cell attachment and proliferation. (paper)
[en] Poly(methacrylic acid-co-2-aminoethyl methacrylate) (MAA-AMA) was simply synthesized by free radical polymerization. Immobilization of 2,4-dihydroxybenzaldehyde on MAA-AMA was done via Schiff base formation to obtain MAA-AMA(BZ). The qualitative and quantitative analyses of immobilization were done by nuclear magnetic resonance spectroscopy. The degree of immobilization of 2,4-dihydroxybenzaldehyde on MAA-AMA was 16–18%. Surface charge and particle size of MAA-AMA(BZ) is pH sensitive. In addition, intermolecular amidation provided cross-link structure at pH 12. The MAA-AMA(BZ) acted as an antifungal against Aspergillus genus with a percentage efficiency up to 25% against A. fumigatus.
[en] Poly-(methyl methacrylate-co-benzyl methacrylate) polarization-maintaining optical fibers are known for their high response to normal stress. In this report, responses to higher stress levels up to 0.45 MPa were investigated. The stress amplitude and direction in the fiber cross section were calculated and analyzed with a coincident mode-field obtained from the near-field pattern. The stress amplitude varies significantly in the horizontal direction and is considered to create multiple phases, explaining the measurement results. To investigate possible permanent deformation, the core yield point profile was analyzed. Although it largely exceeds the average applied stress, the calculated stress distribution indicates that the core could partially experience stress that exceeds the yield point
[en] Plastic scintillators (PS) were made based on benzyl methacrylate and methyl-methacrylate P(BzMA + MMA) copolymer in which the excimer forming rate is by two order lesser than that in polystyrene-based polymer matrix. Studying of these PS light yield demonstrates the importance of migration processes comparing to excimer formation. It is found that to obtain PS with high scintillation efficiency it is necessary to use the polymer base (matrix) in which excimer forming is eliminated but the migration process along the chromophores is maximally favored. To explain the accelerated energy transfer between phenyl chromophores it is proposed to use a mechanism of exchange of that virtual excitons that can propagate along a one-dimensional back-bone of polymer molecule. Clearing the details of mechanism of interaction between chromophores of polymer molecules which is responsible for accelerated radiationless energy transfer enable will determine in future the way of effective plastic scintillators designing.
[en] It is essential to control polymerization parameters in order to reach a specific polymer. A fuzzy controller is proposed to control temperature using reactor and jacket deviations. However, uncertainty exists on a jacket temperature, due to noise disturbance effects. Fuzzy numbers are applied to model this uncertainty. Consequently, a fuzzy trajectory is derived for jacket temperature. Finally, a pseudo-Sugeno fuzzy controller is designed for temperature tracking. The results show the good performance of this controller for control of solution polymerization of methyl methacrylate
[en] The invention concerns a process where the monomers in prepolymerised form are included in a resin, which is further transformed into a resin which can be hardened by irradiation. These resins are suitable as coverings, printing ink carriers, strengthened plastic articles etc. The process provides for: a) The presence of a poly-epoxide with more than a 1.2 oxyran group per molecule, a mixture of a vinyl acid and a mono vinyl monomer to be polymerised and b) that the product obtained in stage a) is converted using an unsaturated monocarbon acid. 9 examples explain details of the invention. (UWI)
[de]Die Erfindung betrifft ein Verfahren, bei dem Monomere in prae-polymerisierter Form in ein Harz eingebaut werden, das dann durch weitere Umsetzung zu einem durch Strahlung haertbaren Harz gestaltet wird. Diese Harze eignen sich als Ueberzuege, Druckfarbentraeger, verstaerkte Plastikartikel usw. Das Verfahren sieht vor, a) in Gegenwart eines Polyepoxids mit mehr als einer 1,2-Oxiran-Gruppe pro Molekuel ein Gemisch aus einer Vinylsaeure und Monovinylmonomeren zu polymerisieren und b) das bei Stufe a) erhaltene Produkt mit einer ungesaettigten Monocarbonsaeure umzusetzen. 9 Beispiele erlaeutern Einzelheiten der Erfindung. (UWI)
[en] The lasing properties and photostability of eighteen aminocoumarins in polymethyl methacrylate, methyl methacrylate, and ethanol excited by an excimer XeCl laser are studied. It is shown that coumarins with a fluorinated methyl group and substituents in the third position of the molecule can be promising active media for lasers on polymer matrices doped with dyes. (lasers)
[en] In this work, the synthesis of associative electrolyte copolymers via the RAFT polymerization technique in solution media is reported. Well-defined polyelectrolytes as multiblock copolymers or multistickers were prepared. Previously, an hydrophilic macroRAFT agent of a statistic copolymer P(MAA-co-EA) was prepared using methacrylic acid (MAA) and ethyl acrylate (EA). Afterwards, chain extensions of the macroagent were carried out by further polymerization of stearyl methacrylate (SMA). At the end, multiblock copolymers (heptablock) were obtained by insertion of three blocks of SMA. All the polymerizations showed a living behavior with the resulting polymers exhibiting a narrow dispersity (Đ ≤ 1.5). The synthesized polymers were characterized by nuclear magnetic resonance (NMR), size exclusion chromatography (SEC) and rheological measurements. Furthermore, it was demonstrated that the insertion of hydrophobic segments into the multiblock copolymers increases considerably the viscosity of the associative electrolyte polymers.