13C-NMR-sequenzanalyes, 3. Alternierende copolyamide aliphatischer und aromatischer aminocarbonsäuren

Copolyamides, containing aliphatic and aromatic amino acid residues in a 1:1 ratio, were obtained by condensation polymerization of 3- and 4-isothiocyanatobenzoyl-ω-amino carboxylic acids ( 1a–e, 2a–c and 3a–d ) at 200°C. ¹H-NMR- and ¹³C-NMR-spectra showed that most of the condensations resulted in polymers with alternating sequences ( 4a–e and 5c–e ). In some cases, however, irregular sequences were obtained due to transamidation reactions.     

Über N-(isothiocyanatoacylamino)carbonsäuren und ihre kondensationspolymerisation zu copolyamiden mit alternierender sequenz

N-Isothiocyanatoacylamino carboxylic acids are crystalline monomers, which were prepared from ω-isothiocyanato carboxylic acid chlorides and various aliphatic or aromatic amino carboxylic acids. Their condensation polymerization to copolyamides was investigated under various conditions. At reaction temperatures ≤200°C exclusively copolyamides with an alternating sequence were formed, whereas at 250°C amide exchange reactions brought about copolyamides with short homologous blocks. The sequence analysis was achieved by ¹H-NMR- or by ¹³C-NMR-spectroscopy. The average molecular weights of all copolyamides were found to be in the range of 5–10000.     

Regulation von Schlüsselenzymen der Biosynthese aromatischer Aminosäuren in Alkaloid-bildenden Kulturen von Penicillium cyclopium w.

In Penicillium cyclopim w., phenylalanin and anthranilate are precursors of the benzodiazepine alkaloids cyclopenin and cyclopenol. The onset and increase of alkaloid biosynthesis in emerged cultures was paralleled by an increase of the in vitro activities of the precursor synthesizing enzymes DAHP synthase¹), chorismate mutase, and anthranilate synthase as well as tryptophan synthase. This increase was most pronounced with the DAHP synthase and, therefore, enabled the cells to maintain a constant level of the “central” precursor, chorismate, in the course of alkaloid production. In contrast, the contents of phe, anthranilate as well as tyr and trp decreased with increasing rate of alkaloid synthesis, indicating that the supply of the immediate precursors did not fully compensate the drain towards alkaloid formation. The strongest decrease was seen with the anthranilate content, which was due to several control mechanisms: the increase of anthranilate consuming reactions prior to the anthranilate synthase, the higher capacity of the alternate. phe producing branch of the aromatic pathway, and the feedback inhibition by trp of anthranilate synthase. The formation of anthranilate most probably was the rate limiting step of alkaloid production.     

Über den thermischen und den thermisch-oxydativen abbau von polyoxymethylenen in lösung 30. Mitt. über polyoxymethylene

High polymers with C?C-double bonds are suited for modifications by simple, chemically obvious reactions provided they exist as solutions in non-polar solvents, free from H₂O and H-acid compounds. Long-chain branching can be achieved in diolefins by FRIEDEL -CRAFTS catalysts. One obtains non-gelled products of much higher molecular weight. By different routes long-chain branching in unsaturated polymers is produced with 4-isocyanate-phenyl sulfene chlorid. Addition type reactions of the NCO-groups incorporated in the polymers produce a variety of copolymers. Cis 1,4-polybutadiene as a model substance is chosen to demonstrate the effect and the range of application of the above-mentioned reagent. The addition reactions of the NCO-group can be studied with NCO-containing polybutadiene in extreme dilution.     

Die temperaturabhängigkeit von abbau und vernetzung bei der γ-bestrahlung von polyäthylenoxid

Three samples of polyethylene oxide (P?_n between 100 and 200) have been γ-irradiated at various temperatures in the pre-gel region. Changes in number and weight average molecular weight have been determined and therefrom 100-eV-yields of crosslinking G(X) and main chain scission G(S) calculated. At room temperature G(S) amounts to 2.0 and G(X) to 1.8. Whereas crosslinking and degradation are only slightly enhanced with increasing temperature below the melting point, a significant increase to G(S) = 4.2 and G(X) = 4.0 occurs at the transition to the liquid state. Above the melting point both G(S) and G(X) are independent of temperature up to the highest temperature (120°C). The increase at the phase transition is considered to be due to the higher mobility of the macromolecules in the liquid state in conjunction with a diminuation of cage recombination of geminate macroradicals produced by main chain scissions. At high temperatures the H-atom-abstraction from intact macromolecules by end group macroradicals is favored. Hereby additional side group macroradicals are formed.     

Messungen zum Aggregationsverhalten perfluorierter Alkansäuren

With the use of various techniques an attempt was made to characterize the aggregates that exist in micellar surfactant solutions of salts of the perfluornonanoic acid. The cmc values of the investigated systems were determined by conductivity and surface tension measurements. Conclusions about the shape of the micellar aggregates were drawn from rheologic and electric birefringence measurements. For the lithium, the ammonium and the tetramethylammonium surfactants the existence of normal micelles with spherical shape and with all surfactant ions lying at the micellar surface was found. The perfluornonanoate surfactants with the ammonium counterions that are partially substituted by alkyl groups showed in all investigations a behaviour that was different from the normal case. It was postulated that these solutions contain emulsion-droplet-like giant micelles with the surfactant ions and counterions solubilized as ion pairs in the interior of the micelles. Some of these giant micelles do not have spherical shape; these solutions showed electric birefringence. In most cases the giant micelles disappeared at higher temperatures. Only normal small micelles with spherical symmetry could then be detected and the measured values were again in the range for values of normal C₈-perfluordetergents. On the basis of the investigated systems reasons and models for the formation of giant micelles are discussed.     

Strukturuntersuchung von polyestern durch direkten abbau im massenspektrometer, 4. Polyester und copolyester der milchsäure und glykolsäure

Polyesters and copolyesters of 2-hydroxyacetic acid (glycolic acid) and 2-hydroxypropionic acid (lactic acid) were investigated by direct pyrolysis in the ion source of a mass spectrometer. Thermal degradation of these polyesters and copolyesters at 10^?6 mbar yields cyclic oligomers which are further degraded by an electron impact induced mechanism by elimination of formaldehyde or acetaldehyde and CO₂ to give characteristic series of linear ions. In the pyrolysis mass spectrum of a copolyester (mole ratio of monomeric units ≈1:1) intact sequences up to 8 monomeric units can be observed.     

Über die kinetik des thermischen und thermooxidativen abbaus von polyäthylenterephthalat

The apparent kinetic parameters of the thermal and the thermal and thermooxidative degradation of poly(ethylene terephthalate) for non-isothermal conditions were evaluated. The dependence of these parameters on the heating rate, the mean molecular weight, and the degree of conversion was also established. It is shown that the degradation in nitrogen probably occurs by a short chain mechanism, while the degradation in air is more complex. In the latter case, the exothermic character of the DTA-curves suggests that the chain degradation reaction is overlapped by oxidation processes.     

Darstellung und eigenschaften von copolyamiden mit oxyethylengruppen in definierter sequenz

The polyamides 3 – 5 were synthesized from α,ω-diamino-substituted oligo(oxyethylene)s ( 1 ) and bis-chlorides of dicarboxylic acids ( 2 ). As copolymers with defined sequences they contain up to five oxyethylene units per repeating unit. Hereby properties like solubility, thermal stability and complexing ability towards alkali metal cations are influenced.     

Über den mit säuren katalysierten abbau von poly-3,4-acrolein. polymere acroleine. 35. Mitt.

The acid-catalyzed degradation of poly-3,4-acrolein was investigated by viscosity and spectroscopic determination of the monomer formed. The degradation occurs predominantly by chain scission; depolymerization is of minor importance. The results are unexpected in comparison to the behaviour of other polymeric aldehydes, they can be explained by the assumption of the formation of a resonance-stabilized chain end during the scission.     

Lichtbeständige äthylencopolymere. Synthese und abbau durch lichteinwirkung

New photostable polyolefin systems containing controlled concentrations of covalently bound ultraviolet screening groups were prepared by copolymerization and rearrangement techniques. This chemical bonding approach, contrasted to the classical additive technique, avoids loss of ultraviolet absorber, permits relatively high concentrations of absorber to be used, and results in better weatherability. Polymers with bound o-hydroxybenzophenone units have the best ultraviolet stability of the absorbers studied. Ethylene/4-methacryloxy-2-hydroxybenzophenone copolymers were blended with high density polyethylene or isotactic polypropylene, permitting high concentrations of polymeric ultraviolet absorber to be retained in these polyolefins for the first time. Other ulraviolet absorbing comonomer units studied include allyl or acryloxy derivatives of o-hydroxyacetophenones, salicylates, 1-(o-hydroxyphenyl)-1,3-propanedione, and dibenzoylmethane.     

13C-NMR-sequenzanalyse, 5. Synthese von nylon-5 und alternierenden copolyamiden der 5-aminovaleriansäure aus 5-isothiocyanatovaleriansäure

Starting with 5-aminovaleric acid ( 2 ) the 5-isothiocyanatovaleric acid trimethylsilylester ( 1 ), 5-isothiocyanatovaleric acid ( 3 ) and its acid chloride ( 4 ) were prepared. The thermal condensation polymerization of 3 yielding nylon-5 was examined under various reaction conditions. In the same way, starting with 4 , N-(5-isothiocyanatovaleryl)-β-alanine ( 5 ) and N-(5-isothiocyanatovaleryl)-4-aminobutyric acid ( 6 ) were synthesized and condensed to alternating copolyamides of 5-aminovaleric acid. The thermal degradation of nylon-3, -4, -5, and -6 as well as of some alternating copolyamides was investigated by thermal gravimetric analysis and the degradation mechanisms are discussed. The ¹³C-NMR-spectra of alternating copolyamides from 5-aminovaleric acid, 4-aminobutyric acid, and β-alanine were compared and relationships between sequences and chemical shifts of the CO signals established.     

Über den licht- und hitzeabbau faseraufbauender hochpolymerer. I. Isolierung von monocarbonsäuren,dicarbonsäuren und alkylaminen aus thermooxydativ abgebautem polycaprolactam

The degradation products of thermo-oxidized polycaprolactam have been analysed. After hydrolysis of the polymer, the homologous aliphatic normal monocarboxylic and dicarboxylic acids could be identified; n-valeric acid and adipic acid are the main products. These facts point to a primary attack of oxygen on the N-vicinal methylene group. Such a mechanism has also been proposed by other authors. Simultaneously produced n-alkylamines indicate a parallel mechanism of degradation different from the reaction previously mentioned.     

Die radikalausbeute beim thermischen zerfall von azoisobuttersäuredinitril in gegenwart von sauerstoff und in methylmethacrylat als lösungsmittel

The efficiency ε of the thermal radical formation from bisazoisobutyronitrile (AIBN) in oxygen-containing solutions, was determined by two direct analytical methods, which complement one another. The first consists in the gaschromatographic determination of tetramethyl succinodinitrile, which originates from combination of the primarily formed 2-cyanoisopropyl radicals; it yields a value for (1-ε). The second method consists in the jodometric determination of 2-cyanoisopropyl hydroperoxide and p-benzoquinone which originate from those radicals which have escaped from the primary combination reaction and which latterly undergo a seavengering-reaction with hydroquinone; it yields value for ε. For the system methylmethacrylate/AIBN/O₂/hydroquinone and for 90°C both methods correspondingly result ε + 0.810 ± 0.005. Between 70 and 100°C ε increases linearely from 0.785 ± 0.005 to 0.833 ± 0.005. For n-propyl acetate and toluene as the solvents and at 90°C the same ε-value as for methyl methacrylate was found, i.e. 0.813 ± 0.005 and 0.810 ± 0.005, respectively.     

Wirkung von Ölen und Fettsäuren auf Wachstum und Enzymbildung bei Thermoactinomyces vulgaris III. Einfluß von Kulturgefäßen,Stammaterial und Medienzusammensetzung

The influence of rape-oil as antifoam agent on growth and protease synthesis of T. vulgaris was studied. The turbulence and the aeration conditions caused by the culture vessel have a fundamental importance for the so-called oil effect. A higher aeration rate induces an enhanced lysis of the mycelium and consequently a reduced enzyme synthesis. The tentency to lysis of the mycelium at different selectants is variable. The addition of oil to the culture medium reduces this tendency and promotes the protease production. The oil effect on the enzyme synthesis is higher in deficient medium than in full one.     

Das Verhalten von isotaktischen Polyacrylsäuren im Organismus. Verteilung und Ausscheidung bei Mäusen

Isopropyl acrylate-2,3-¹⁴C and isopropyl acrylate-2,3-³H were polymerized using anionic initiators. The isotactic polymers were fractionated by fractional precipitation and characterized. The polymer fractions were hydrolysed to polyacrylic acids by trifluoroacetic acid. Aqueous solutions of these radioactive labelled polyacrylic acids were injected intravenously to mice in amounts of 40 to 100mg/kg. Distribution in organs and the excretion were studied. About two thirds of the dose were excreted within the first two days with a half-life of about 0,5 days. Further excretion took place with a half-life of about six weeks. Distribution in the organism was not uniform; the highest concentrations were found in spleen, bones, and liver, i.e. organs being parts of the reticuloendothelial system. A relationship between organ concentration and molecular weight of the polyacrylic acid was only observed in the spleen. Nine weeks after injection about 10% of the dose were still retained in the organism, mainly in the skeleton.