Miroslav Marek
Academy of Sciences of the Czech Republic
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Featured researches published by Miroslav Marek.
European Polymer Journal | 1997
Miroslav Marek; Eduard Brynda; Z. Pientka; Jan Schauer
Abstract Composite membranes with an ultra-thin polyimide separation layer were prepared by two-dimensional UV crosslinking of Langmuir-Blodgett films of a salt of polyamic acid based on 4,4′-hexafluoroisopropylidenebis(phthalic anhydride) and 2-(methacryloyloxy)ethyl 3,5-diaminobenzoate on the argon/water interface and then its deposition onto the surface of a porous support and by subsequent thermal imidization. Separation factors for CO2/N2, α = 6.4, and for O2/N2, α = 2.4, at permeation rates of the order 10−6 cm3 (STP)/(cm2 s cm Hg) were reached.
Polymer | 1996
Miroslav Marek; Eduard Brynda; Milan Houska; Jan Schauer; Vladimír Hynek; Milan Šípek
Abstract Composite membranes with an ultra-thin polyimide separation layer have been prepared by the deposition of dimethylalkylammonium salt of polyamic acid on a poly(phenylene oxide) porous support layer by the Langmuir—Blodgett technique and subsequent thermal cyclization of the polyimide precursor. In spite of a relatively mild thermal treatment, complete cyclization was achieved as observed by Fourier transform infra-red spectroscopy. The composite membrane with polyimide ultra-thin separation layer exhibited a considerably high permeation rate, maintaining a good selectivity.
Polymer | 1994
Miroslav Marek; Danica Doskočilová; Pavel Schmidt; Bohdan Schneider; Jaroslav Kříž; J. Labský; Rudolf Puffr
Abstract New soluble aromatic polyimides have been prepared from 4,4′-(hexafluoroisopropylidene)bis(phthalic anhydride) (6FDA) and 4,4′-(alkylenediyldioxy)dianilines. Their structures were determined by i.r., 1 H n.m.r. and 13 C n.m.r. spectroscopic measurements, based on model compounds prepared by reacting 6FDA with p -anisidine. These polymers show low glass transition temperatures and good solubility in various solvents, and are stable up to 440°C in a nitrogen atmosphere.
Carbohydrate Research | 1992
Karel Kefurt; Z. Kefurtová; Jiří Jarý; Irena Horáková; Miroslav Marek
Abstract Enzymically catalysed, partial deacetylation of the 5,6-diacetates of 3-deoxy-1,2- O -isopropylidene-α- d - ribo -hexofuranose and 1,2- O -isopropylidene-α- d -gluco- and -allo-furanose with different substituents at C-3(OAc, OMe, NHAc) gives the 5-acetate, which migrates rapidly to give the 6-acetate. The initial rate of deacetylation depends on the size of the 3-substituent and the configuration at C-3.
Biocatalysis and Biotransformation | 1989
Miroslav Marek; Ivan Medonos; Karel Kefurt; Jiria Jary
The deacetyiation of methyl 2,3,4-tri-O-acetyl-β-D-ylopyranoside was studied under different conditions of alkaline and enzymic hydrolysis. During enzymic deacetylation using porcine liver esterase a considerably higher amount of partially acetylated derivatives was observed in contrast to chemical hydrolysis.
Journal of Macromolecular Science, Part A | 1996
Miroslav Marek; Bohdan Schneider; D. Hlavatá; J. Labský; M. Bleha
Abstract Polyimides based on 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-(alkane-1,n-diyldioxy)dianilines were prepared via the corresponding polyamic acids and characterized by solid-state 13C-NMR and IR spectroscopy. As shown by x-ray diffraction measurements, the polyimides are semicrystalline whereas the polyamic acids are entirely amorphous. Glass transition temperatures of the polyimides are lower compared with polyimides without flexible linkages. The polyimides are stable up to 400°C in nitrogen atmosphere.
Biocatalysis and Biotransformation | 1992
Miroslav Marek; Ivan Raich; Karel Kefurt; Jiří Jarý; Inge Rouwenhorst
Enzymic deacetylation of methyl 2,3-di-O-acaetyl-α- and β-D-threofuranoside using porcine liver esterase affords monoacetates only (in the case of the α-anomer, the 3-O-acetylderivative exclusively) without any further hydrolysis to the corresponding diols.
Polymer International | 1999
Miroslav Marek; Petr Holler; Pavel Schmidt; Bohdan Schneider; Jana Kovářová; Ivan Kelnar; Jindřich Pytela; Miloslav Sufčák
Polyimides containing polybutadiene blocks were prepared by copolycondensation of benzophenone-3,3′,4,4′-tetracarboxylic dianhydride, diphenylmethane-4,4′-diisocyanate and isocyanate-endcapped polybutadiene LBD-3000. 13C NMR CP-MAS and FTIR spectroscopies were used to determine the chemical structure of the copolymers. TGA showed that the thermal stability of the copolymers in inert atmosphere is almost independent of the polybutadiene content in the copolymer (as follows from the temperature of 10% and 20% weight loss). Stress–strain experiments showed that copolymers containing amounts of polybutadiene higher than 59 wt% exhibited elastomeric behaviour. © 1999 Society of Chemical Industry
European Polymer Journal | 1995
Miroslav Marek; Jaroslav Stehlíček; Danica Doskočilová
Abstract Low molecular weight aromatic polyamides of the meta-type which bear N-acyl-6-hexanelactam end-groups were prepared, characterized by NMR and utilized as initiators of the anionic polymerization of 6-hexanelactam. The resulting block copolymers poly(6-hexanelactam)-block-poly(-isophthalic acid-alt-2-methyl-1,3-phenylenediamine)-block-poly-(6-hexanelactam) were characterized by NMR, DSC, TGA, X-ray diffraction and microscopy of solution-cast films and compared with an aramide-polyamide 6 blend also prepared by polymerization.
Biocatalysis and Biotransformation | 1989
Miroslav Marek; Zuzana Novotná; Jiri Jary; Veroslava Kociková
Benzyl β-D-glucopyranoside was prepared by an enzyme-catalysed direct reaction between D-glucose, or better cellobiose, and benzyl alcohol in the presence of a minimum amount of water. The enzyme β-glucosidase was used in the immobilized form (adsorbed onto macroporous polyethylene terephthalate or covalently bound on polyglycidyl methacrylate), enabling multiple application.