Jürgen Engelhardt - Academia.edu (original) (raw)
Papers by Jürgen Engelhardt
Perspektiven nachwachsender Rohstoffe in der Chemie
The demand for biodegradable materials can be traced to the general shortage of landfill space, t... more The demand for biodegradable materials can be traced to the general shortage of landfill space, the necessity to use resources with low environmental impact focusing on CO 2 neutrality and end-user benefits in various fields of application. For the first two aspects the use of rapidly renewable raw materials is imperative. Starch is a raw material of this kind which has gained some significance in the field of biodegradable materials. Cellulose, being a constituent of wood, is regenerated in much larger quantities than starch by natural photosynthesis from CO 2 and water. There is substantial, trough so far little exploited, potential in its continously renewable quantity and in nature's molecular synthesis capabilities. In the category of cellulose-based materials, two main groups are used on an industrial scale. The first is the group of regenerated celluloses which with conventional and new manufacturing processes are only suitable for fibre and film production and can not be processed into moulded articles. The second group comprises the cellulose acetates and their mixed esters which are only biodegradable under specific conditions. Based on general considerations on the correlation between biodegradability and molecular structure, cellulose derivatives allowing both thermoplastic processing and post-consumer disposal via biological decomposition have been developed. The paper deals with the relationship between biodegradability, thermoplastic behaviour and material properties as well as the resultant synthesis strategy and its realization.
Die Erfindung betrifft ein Verfahren zur Herstellung aminoalkoxylgruppenhaltiger Polysaccharide u... more Die Erfindung betrifft ein Verfahren zur Herstellung aminoalkoxylgruppenhaltiger Polysaccharide und Polysaccharidderivate, bei dem man a) ein Polysaccharid oder Polysaccharidderivat in einem Gemisch aus einem wassermischbaren aprotischen Losungsmittel und Wasser dispergiert und b) das Polysaccharid oder Polysaccharidderivat mit einer anorganischen Base alkalisiert und c) wahrend der Alkalisierung die eingesetzte Menge Wasser im Bereich zwischen 1 und 55 Mol Wasser pro Anhydroglycoseeinheit des Polysaccharids oder Polysaccharidderivates einstellt und d) anschliesend eine Aminierung mit einem Veretherungsreagenz bei gegebenenfalls erhohter Temperatur durchfuhrt und dann e) gegebenenfalls neutralisiert und f) das Reaktionsprodukt abfiltriert, wascht und dann gegebenenfalls trocknet und mahlt. Ein weiterer Gegenstand der Erfindung sind so hergestellte aminogruppenhaltige Polysaccharidderivate mit einem Gesamtsubstitutionsgrad.
Die vorliegende Erfindung betrifft die kontinuierliche Herstellung besonders wasserarmer, alkohol... more Die vorliegende Erfindung betrifft die kontinuierliche Herstellung besonders wasserarmer, alkohol- und weichmacherfreier Nitrocellulose-Fertiglosungen durch partielle destillative Fallfilm-Eindampfung von vergleichsweise wasserreichen, gegebenenfalls emulsionsartigen Nitrocellulose-Rohlosungen, die vorzugsweise durch Auflosung von bekanntermasen herstellungsbedingt zunachst wasserfeuchten Nitrocellulosen der gebrauchlichen festen Darbietungsformen in bevorzugt Essigsaureethylester bereitgestellt werden.
La presente invention concerne un procede de fabrication de produits d'ether de cellulose car... more La presente invention concerne un procede de fabrication de produits d'ether de cellulose caracterises en ce que des polymeres super-absorbants (SAP) sont seches, malaxes ou seches par malaxage avec de l'ether de cellulose humide. L'invention concerne egalement les produits d'ether de cellulose fabriques au moyen dudit procede.
Disclosed is a method for the preparation of amino group-containing cellulose derivatives by reac... more Disclosed is a method for the preparation of amino group-containing cellulose derivatives by reaction of alkalized cellulose or alkalized cellulose derivatives with reagents of the general formula X- (CH in which X is chlorine, bromine, iodine or a sulfonic acid R'SO n must be at least 2, the radicals R characterized in that water is used as reaction medium, and the ratio of cellulose to water is 1: 5 to 1: 40 moles per mole of anhydroglucose unit (AGU) is. Also described are amino group-containing cellulose derivatives having certain total substitution, and their use in cosmetic formulations, in water treatment or papermaking.
Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennezeichnet, dass die... more Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennezeichnet, dass die Additive irreversibel vernetzte Celluloseether mit gelartigen rheologischen Eigenschaften enthalten. Ebenfalls beschrieben wird die Verwendung irreversibel vernetzter Cellulosederivate als Additive zur Extrusion von Baustoffsystemen sowie ein Extrusionsverfahren fur Baustoffsysteme.
Die Erfindung betrifft ein Verfahren zur Herstellung von Starkephosphaten mit geringem Carbamatge... more Die Erfindung betrifft ein Verfahren zur Herstellung von Starkephosphaten mit geringem Carbamatgehalt, die einen hohen Substituierungsgrad hinsichtlich der Phosphatgruppen aufweisen. Ebenso betrifft die Erfindung derart hergestellte Starkephosphate.
L'invention concerne des systemes comprenant des ethers esters de polysaccharide et des princ... more L'invention concerne des systemes comprenant des ethers esters de polysaccharide et des principes actifs agrochimiques, qui contiennent eventuellement des additifs classiques et sont biodegradables.
Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu... more Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu deren Herstellung. Die erhaltenen cellulosebesierten Partikel weisen gewichts- bzw. volumengemittelte Partikelgrosen von weniger als 300 nm auf. Die Darstellung dieser Nanopartikel erfolgt aus geringfugig oxiderter Cellulose und durch Eintrag von Energie nach oder wahrend der Dispersion in ein wasserhaltiges Medium.
Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu... more Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu deren Herstellung. Die erhaltenen cellulosebasierten Partikel weisen gewichts- bzw. volumengemittelte Partikelgrosen von weniger als 300 nm auf. Die Darstellung dieser Nanopartikel erfolgt aus amorpher Cellulose bzw. durch Amorphisierung von Cellulose, optionaler anschliesender Hydrolyse und durch Eintrag von Energie nach oder wahrend der Dispersion in ein wasserhaltiges Medium.
Verfahren zur Herstellung hochsubstituierter Starkephosphate, bei dem a) in einem Vorbehandlungss... more Verfahren zur Herstellung hochsubstituierter Starkephosphate, bei dem a) in einem Vorbehandlungsschritt die Starke in einem Gemisch aus Phosphatierungsmittel, Wasser und, fur den Fall, dass das Phosphatierungsmittel frei von Harnstoff ist, Harnstoff aufgelost wird, b) das Wasser aus dem Gemisch in Schritt a) entfernt wird und c) anschliesend eine thermische Umsetzung zum Starkephosphat erfolgt.
Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennzeichnet, dass die ... more Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennzeichnet, dass die Additive irreversibel vernetzte Celluloseether mit gel-artigen rheologischen Eigenschaften enthalten. Ebenfalls beschrieben wird die Verwendung irreversibel vemetzter Cellulosederivate als Additive zur Extrusion von Baustoffsystemen sowie ein Extrusionsverfahren fur Baustoffsysteme.
The present invention relates to a process for recovering hemicellulose from lignocellulosic mate... more The present invention relates to a process for recovering hemicellulose from lignocellulosic material in high yield and purity.
Various copolyesters were synthesized from 4,4′-dihydroxybiphenyl and combinations of two or thre... more Various copolyesters were synthesized from 4,4′-dihydroxybiphenyl and combinations of two or three differently substituted terephthalic acids. Various synthetic methods were studied; polycondensations of terephthaloyl dichlorides in dry pyridine gave the highest molecular weights. All copolyesters are semicrystalline and form a nematic melt above their melting points. Several copolyesters are well soluble in aprotic organic solvents, such as dichloromethane, N,N-dimethyl-formamide (DMF), methyl benzoate or chlorobenzene. A blend of such a soluble polyester (5 wt.-%) with bisphenol-A polycarbonate (poly(oxycarbonyl-oxy-1,4-phenyleneisopropylidene-1,4-phenylene)) was prepared from a cosolvent and various mechanical data were measured. These data were compared with those of an aromatic thermotropic polycarbonate.
Polyesters were prepared from 4,4′-dihydroxybiphenyl and various aryloxyterephthalic acids or var... more Polyesters were prepared from 4,4′-dihydroxybiphenyl and various aryloxyterephthalic acids or various disubstituted terephthalic acids. The aryloxyterephthalic acids were prepared by nucleophilic substitution of dimethyl nitroterephthalate with phenoxide ions. The disubstituted terephthalic acids were synthesized by double alkylation of diethyl 2,5-dihydroxyterephthalate with various alkyl bromides containing aromatic rings in the ω-position. The silyl method was primarily used for the polycondensation procedure. The resulting polyesters were characterized by elemental analyses, viscosity measurements, wide-angle X-ray scattering and differential scanning calorimetry measurements, and by optical microscopy. All polyesters proved to be semicrystalline, meltable materials forming a nematic phase above their melting points. The substituents of terephthalic acid enhance the solubility in organic solvents, so that all polyesters are soluble in CH2Cl2/trifluoroacetic acid mixtures and some of them even in hot N,N-dimethyl-formamide or methyl benzoate.
A not perfectly pure 1,4-bis(trimethylsilylamino)-2,5-bis(trimethylsilylthio)benzene was prepared... more A not perfectly pure 1,4-bis(trimethylsilylamino)-2,5-bis(trimethylsilylthio)benzene was prepared as starting material for all condensations. Condensations with 4-chlorobenzoyl chloride under a variety of reaction conditions revealed formation of benzobisthiazoles at temperatures ≥250°C. Condensation with various aryloxy or bisalkoxyterephthaloyl chlorides in an one-pot procedure yielded substituted poly(benzobisthiazole)s. All poly(benzobisthiazole)s were soluble in mixtures of dichloromethane or chloroform and trifluoroacetic acid (TFA). Inherent viscosities up to 2,0 dl/g were found in this solvent system. Neither homo- nor copoly(benzobisthiazole)s formed a freely flowing melt up to 450°C, where thermal degradation beings to affect the properties. Thermogravimetric analyses in air proved that aryloxy-substituted polymers possess a significantly greater thermostability than alkoxy-substituted ones.
Substituted polybenzodioxazoles were synthesized from silylated 2,5-diaminohydroquinone (5) and v... more Substituted polybenzodioxazoles were synthesized from silylated 2,5-diaminohydroquinone (5) and various aryloxyterephthaloyl dichlorides (6). Either a “one-pot procedure” or a two step procedure was used. In the latter case the silylated monomer was condensed with a terephthaloyl dichloride at −15°C in 1-methyl-2-pyrrolidone and the isolated polymer 8 was cyclized at 350°C in an inert reaction medium. The optimum reaction conditions were determined for a low-molecular-weight model and the reaction products were characterized. The substituted polybenzodioxazoles are soluble in dichloromethane/trifluoroacetic acid mixtures, yet, they do not form a mobile melt up to 600°C.
Starch - Stärke, 2004
Carboxymethyl starches (CMS) with a degree of substitution (DS) in the range of 0.5 to 1.5 and re... more Carboxymethyl starches (CMS) with a degree of substitution (DS) in the range of 0.5 to 1.5 and reagent yields about 70% were synthesised under heterogeneous reaction conditions. Starting from a standard procedure for manufacturing low substituted CMS the molar ratios of the reagents were increased. Under these conditions starch particles agglomerated during the reaction and the stirrer stopped. The reaction conditions (pulp density, addition of dispersing and water binding agents, pressure, sequence of reagents addition, reaction time, temperature, starch variety, etc.) were varied to find the best process conditions for optimum reaction efficiencies and product properties. If an amylose-free starch, e.g. waxy corn starch is used as starting material, the obtained products are completely soluble in water to form a clear solution. The products are good viscosity regulators. Using a 2% aqueous solution a wide range of viscosity (1-90 000 mPa s) can be adjusted. The calcium-binding capacity and the biodegradability of the products were investigated.
Polymer, 1996
A set of carboxymethylcellulose (CMC) samples was varied in degree of substitution (DS) from 0.71... more A set of carboxymethylcellulose (CMC) samples was varied in degree of substitution (DS) from 0.71 to 2.95, with the partial degree of substitution being raised uniformly at positions C2, C3 and C6, so that a homologous series of CMC was made available. A further set of samples varied in molar mass from 200 000 to 2 000 000 g mo1-1 at a constant DS of,-~ 1. The chemical structural parameters were determined by n.m.r. spectroscopy, showing that quantification of the degree of substitution at position C6 may be distorted by impurities of glycolic acid. The mean molar masses, for establishing the [zl]-M relationship, were determined by multiangle laser light scattering preceded by size exclusion chromatography. The influence of concentration on zero-shear viscosity was given by ~70 cx c 43, whereas the influence of the molar mass was determined by ~0 cx M 39. An increasing DS within a homologous series influences the viscosity in different solvents (H20 0.01 M NaC1, 0.1 M NaC1) at low polyelectrolytic concentrations. Surprisingly, the viscosity for all the CMC samples can be predicted by the single equation: r/0[Pa s] = 8.91 x 10-4 + 1.30 × 10-5 cM~ 9 + 5.33 x 10-8cZM L8 q-4.60 x 10-15c434M~ 91 at T = 298 K in 0.01 M NaC1. Increasing the DS up to a value of,,~ 1 improves the solubility characteristics (increases the viscosity), whereas above DS ~ 1 this effect is overlapped by degradation of the molar mass. It was also possible to quantitatively determine the viscoelasticity as a function of frequency and molecular parameters.
Perspektiven nachwachsender Rohstoffe in der Chemie
The demand for biodegradable materials can be traced to the general shortage of landfill space, t... more The demand for biodegradable materials can be traced to the general shortage of landfill space, the necessity to use resources with low environmental impact focusing on CO 2 neutrality and end-user benefits in various fields of application. For the first two aspects the use of rapidly renewable raw materials is imperative. Starch is a raw material of this kind which has gained some significance in the field of biodegradable materials. Cellulose, being a constituent of wood, is regenerated in much larger quantities than starch by natural photosynthesis from CO 2 and water. There is substantial, trough so far little exploited, potential in its continously renewable quantity and in nature's molecular synthesis capabilities. In the category of cellulose-based materials, two main groups are used on an industrial scale. The first is the group of regenerated celluloses which with conventional and new manufacturing processes are only suitable for fibre and film production and can not be processed into moulded articles. The second group comprises the cellulose acetates and their mixed esters which are only biodegradable under specific conditions. Based on general considerations on the correlation between biodegradability and molecular structure, cellulose derivatives allowing both thermoplastic processing and post-consumer disposal via biological decomposition have been developed. The paper deals with the relationship between biodegradability, thermoplastic behaviour and material properties as well as the resultant synthesis strategy and its realization.
Die Erfindung betrifft ein Verfahren zur Herstellung aminoalkoxylgruppenhaltiger Polysaccharide u... more Die Erfindung betrifft ein Verfahren zur Herstellung aminoalkoxylgruppenhaltiger Polysaccharide und Polysaccharidderivate, bei dem man a) ein Polysaccharid oder Polysaccharidderivat in einem Gemisch aus einem wassermischbaren aprotischen Losungsmittel und Wasser dispergiert und b) das Polysaccharid oder Polysaccharidderivat mit einer anorganischen Base alkalisiert und c) wahrend der Alkalisierung die eingesetzte Menge Wasser im Bereich zwischen 1 und 55 Mol Wasser pro Anhydroglycoseeinheit des Polysaccharids oder Polysaccharidderivates einstellt und d) anschliesend eine Aminierung mit einem Veretherungsreagenz bei gegebenenfalls erhohter Temperatur durchfuhrt und dann e) gegebenenfalls neutralisiert und f) das Reaktionsprodukt abfiltriert, wascht und dann gegebenenfalls trocknet und mahlt. Ein weiterer Gegenstand der Erfindung sind so hergestellte aminogruppenhaltige Polysaccharidderivate mit einem Gesamtsubstitutionsgrad.
Die vorliegende Erfindung betrifft die kontinuierliche Herstellung besonders wasserarmer, alkohol... more Die vorliegende Erfindung betrifft die kontinuierliche Herstellung besonders wasserarmer, alkohol- und weichmacherfreier Nitrocellulose-Fertiglosungen durch partielle destillative Fallfilm-Eindampfung von vergleichsweise wasserreichen, gegebenenfalls emulsionsartigen Nitrocellulose-Rohlosungen, die vorzugsweise durch Auflosung von bekanntermasen herstellungsbedingt zunachst wasserfeuchten Nitrocellulosen der gebrauchlichen festen Darbietungsformen in bevorzugt Essigsaureethylester bereitgestellt werden.
La presente invention concerne un procede de fabrication de produits d'ether de cellulose car... more La presente invention concerne un procede de fabrication de produits d'ether de cellulose caracterises en ce que des polymeres super-absorbants (SAP) sont seches, malaxes ou seches par malaxage avec de l'ether de cellulose humide. L'invention concerne egalement les produits d'ether de cellulose fabriques au moyen dudit procede.
Disclosed is a method for the preparation of amino group-containing cellulose derivatives by reac... more Disclosed is a method for the preparation of amino group-containing cellulose derivatives by reaction of alkalized cellulose or alkalized cellulose derivatives with reagents of the general formula X- (CH in which X is chlorine, bromine, iodine or a sulfonic acid R'SO n must be at least 2, the radicals R characterized in that water is used as reaction medium, and the ratio of cellulose to water is 1: 5 to 1: 40 moles per mole of anhydroglucose unit (AGU) is. Also described are amino group-containing cellulose derivatives having certain total substitution, and their use in cosmetic formulations, in water treatment or papermaking.
Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennezeichnet, dass die... more Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennezeichnet, dass die Additive irreversibel vernetzte Celluloseether mit gelartigen rheologischen Eigenschaften enthalten. Ebenfalls beschrieben wird die Verwendung irreversibel vernetzter Cellulosederivate als Additive zur Extrusion von Baustoffsystemen sowie ein Extrusionsverfahren fur Baustoffsysteme.
Die Erfindung betrifft ein Verfahren zur Herstellung von Starkephosphaten mit geringem Carbamatge... more Die Erfindung betrifft ein Verfahren zur Herstellung von Starkephosphaten mit geringem Carbamatgehalt, die einen hohen Substituierungsgrad hinsichtlich der Phosphatgruppen aufweisen. Ebenso betrifft die Erfindung derart hergestellte Starkephosphate.
L'invention concerne des systemes comprenant des ethers esters de polysaccharide et des princ... more L'invention concerne des systemes comprenant des ethers esters de polysaccharide et des principes actifs agrochimiques, qui contiennent eventuellement des additifs classiques et sont biodegradables.
Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu... more Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu deren Herstellung. Die erhaltenen cellulosebesierten Partikel weisen gewichts- bzw. volumengemittelte Partikelgrosen von weniger als 300 nm auf. Die Darstellung dieser Nanopartikel erfolgt aus geringfugig oxiderter Cellulose und durch Eintrag von Energie nach oder wahrend der Dispersion in ein wasserhaltiges Medium.
Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu... more Die vorliegende Erfindung betrifft neuartige nanoskalige Cellulosepartikel sowie ein Verfahren zu deren Herstellung. Die erhaltenen cellulosebasierten Partikel weisen gewichts- bzw. volumengemittelte Partikelgrosen von weniger als 300 nm auf. Die Darstellung dieser Nanopartikel erfolgt aus amorpher Cellulose bzw. durch Amorphisierung von Cellulose, optionaler anschliesender Hydrolyse und durch Eintrag von Energie nach oder wahrend der Dispersion in ein wasserhaltiges Medium.
Verfahren zur Herstellung hochsubstituierter Starkephosphate, bei dem a) in einem Vorbehandlungss... more Verfahren zur Herstellung hochsubstituierter Starkephosphate, bei dem a) in einem Vorbehandlungsschritt die Starke in einem Gemisch aus Phosphatierungsmittel, Wasser und, fur den Fall, dass das Phosphatierungsmittel frei von Harnstoff ist, Harnstoff aufgelost wird, b) das Wasser aus dem Gemisch in Schritt a) entfernt wird und c) anschliesend eine thermische Umsetzung zum Starkephosphat erfolgt.
Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennzeichnet, dass die ... more Beschrieben werden Additive zur Extrusion von Baustoffsystemen, dadurch gekennzeichnet, dass die Additive irreversibel vernetzte Celluloseether mit gel-artigen rheologischen Eigenschaften enthalten. Ebenfalls beschrieben wird die Verwendung irreversibel vemetzter Cellulosederivate als Additive zur Extrusion von Baustoffsystemen sowie ein Extrusionsverfahren fur Baustoffsysteme.
The present invention relates to a process for recovering hemicellulose from lignocellulosic mate... more The present invention relates to a process for recovering hemicellulose from lignocellulosic material in high yield and purity.
Various copolyesters were synthesized from 4,4′-dihydroxybiphenyl and combinations of two or thre... more Various copolyesters were synthesized from 4,4′-dihydroxybiphenyl and combinations of two or three differently substituted terephthalic acids. Various synthetic methods were studied; polycondensations of terephthaloyl dichlorides in dry pyridine gave the highest molecular weights. All copolyesters are semicrystalline and form a nematic melt above their melting points. Several copolyesters are well soluble in aprotic organic solvents, such as dichloromethane, N,N-dimethyl-formamide (DMF), methyl benzoate or chlorobenzene. A blend of such a soluble polyester (5 wt.-%) with bisphenol-A polycarbonate (poly(oxycarbonyl-oxy-1,4-phenyleneisopropylidene-1,4-phenylene)) was prepared from a cosolvent and various mechanical data were measured. These data were compared with those of an aromatic thermotropic polycarbonate.
Polyesters were prepared from 4,4′-dihydroxybiphenyl and various aryloxyterephthalic acids or var... more Polyesters were prepared from 4,4′-dihydroxybiphenyl and various aryloxyterephthalic acids or various disubstituted terephthalic acids. The aryloxyterephthalic acids were prepared by nucleophilic substitution of dimethyl nitroterephthalate with phenoxide ions. The disubstituted terephthalic acids were synthesized by double alkylation of diethyl 2,5-dihydroxyterephthalate with various alkyl bromides containing aromatic rings in the ω-position. The silyl method was primarily used for the polycondensation procedure. The resulting polyesters were characterized by elemental analyses, viscosity measurements, wide-angle X-ray scattering and differential scanning calorimetry measurements, and by optical microscopy. All polyesters proved to be semicrystalline, meltable materials forming a nematic phase above their melting points. The substituents of terephthalic acid enhance the solubility in organic solvents, so that all polyesters are soluble in CH2Cl2/trifluoroacetic acid mixtures and some of them even in hot N,N-dimethyl-formamide or methyl benzoate.
A not perfectly pure 1,4-bis(trimethylsilylamino)-2,5-bis(trimethylsilylthio)benzene was prepared... more A not perfectly pure 1,4-bis(trimethylsilylamino)-2,5-bis(trimethylsilylthio)benzene was prepared as starting material for all condensations. Condensations with 4-chlorobenzoyl chloride under a variety of reaction conditions revealed formation of benzobisthiazoles at temperatures ≥250°C. Condensation with various aryloxy or bisalkoxyterephthaloyl chlorides in an one-pot procedure yielded substituted poly(benzobisthiazole)s. All poly(benzobisthiazole)s were soluble in mixtures of dichloromethane or chloroform and trifluoroacetic acid (TFA). Inherent viscosities up to 2,0 dl/g were found in this solvent system. Neither homo- nor copoly(benzobisthiazole)s formed a freely flowing melt up to 450°C, where thermal degradation beings to affect the properties. Thermogravimetric analyses in air proved that aryloxy-substituted polymers possess a significantly greater thermostability than alkoxy-substituted ones.
Substituted polybenzodioxazoles were synthesized from silylated 2,5-diaminohydroquinone (5) and v... more Substituted polybenzodioxazoles were synthesized from silylated 2,5-diaminohydroquinone (5) and various aryloxyterephthaloyl dichlorides (6). Either a “one-pot procedure” or a two step procedure was used. In the latter case the silylated monomer was condensed with a terephthaloyl dichloride at −15°C in 1-methyl-2-pyrrolidone and the isolated polymer 8 was cyclized at 350°C in an inert reaction medium. The optimum reaction conditions were determined for a low-molecular-weight model and the reaction products were characterized. The substituted polybenzodioxazoles are soluble in dichloromethane/trifluoroacetic acid mixtures, yet, they do not form a mobile melt up to 600°C.
Starch - Stärke, 2004
Carboxymethyl starches (CMS) with a degree of substitution (DS) in the range of 0.5 to 1.5 and re... more Carboxymethyl starches (CMS) with a degree of substitution (DS) in the range of 0.5 to 1.5 and reagent yields about 70% were synthesised under heterogeneous reaction conditions. Starting from a standard procedure for manufacturing low substituted CMS the molar ratios of the reagents were increased. Under these conditions starch particles agglomerated during the reaction and the stirrer stopped. The reaction conditions (pulp density, addition of dispersing and water binding agents, pressure, sequence of reagents addition, reaction time, temperature, starch variety, etc.) were varied to find the best process conditions for optimum reaction efficiencies and product properties. If an amylose-free starch, e.g. waxy corn starch is used as starting material, the obtained products are completely soluble in water to form a clear solution. The products are good viscosity regulators. Using a 2% aqueous solution a wide range of viscosity (1-90 000 mPa s) can be adjusted. The calcium-binding capacity and the biodegradability of the products were investigated.
Polymer, 1996
A set of carboxymethylcellulose (CMC) samples was varied in degree of substitution (DS) from 0.71... more A set of carboxymethylcellulose (CMC) samples was varied in degree of substitution (DS) from 0.71 to 2.95, with the partial degree of substitution being raised uniformly at positions C2, C3 and C6, so that a homologous series of CMC was made available. A further set of samples varied in molar mass from 200 000 to 2 000 000 g mo1-1 at a constant DS of,-~ 1. The chemical structural parameters were determined by n.m.r. spectroscopy, showing that quantification of the degree of substitution at position C6 may be distorted by impurities of glycolic acid. The mean molar masses, for establishing the [zl]-M relationship, were determined by multiangle laser light scattering preceded by size exclusion chromatography. The influence of concentration on zero-shear viscosity was given by ~70 cx c 43, whereas the influence of the molar mass was determined by ~0 cx M 39. An increasing DS within a homologous series influences the viscosity in different solvents (H20 0.01 M NaC1, 0.1 M NaC1) at low polyelectrolytic concentrations. Surprisingly, the viscosity for all the CMC samples can be predicted by the single equation: r/0[Pa s] = 8.91 x 10-4 + 1.30 × 10-5 cM~ 9 + 5.33 x 10-8cZM L8 q-4.60 x 10-15c434M~ 91 at T = 298 K in 0.01 M NaC1. Increasing the DS up to a value of,,~ 1 improves the solubility characteristics (increases the viscosity), whereas above DS ~ 1 this effect is overlapped by degradation of the molar mass. It was also possible to quantitatively determine the viscoelasticity as a function of frequency and molecular parameters.