Reaktionen mit Silylaziden, 7. Über 4-Isocyanatocarbonsäure-trimethylsilylester und 4-Aminocarbonsäure-N-carbonsäureanhydride

Trimethylsilylesters of various 4-isocyanatocarboxylic acids ( 6a–h, 13, 14, 16, 17 ) were prepared by the reaction of cyclic 1,3-dicarboxylic acid anhydrides ( 10, 11, 12, 15 ) with trimethylsilyl azide ( 9 ). Mild hydrolysis of these silylesters yields 4-isocyanatocarboxylic acids, which in every case undergo addition polymerization to give unstable oligo(4-aminocarboxylic acid N-carboxylic anhydrides). Simultaneously cyclisation to crystalline, seven membered 4-aminocarboxylic acid-NCA ( 20—25 ) occurs. These cyclic NCA, however, cannot be observed or isolated in the case of all 4-isocyanatocarboxylic acids. Heat or basic catalysis induces decarboxylation of both linear and cyclic NCA with the formation of oligoamides ( 36, 37 ). Simultaneously, ring contraction occurs to give five membered lactams (26–30), which are the main products of thermal decarboxy-lation. In no case high molecular weight polyamides were obtained.     

Einfluß niedermolekularer zusätze auf die viskosität der polyäthylenschmelze

An investigation was made of the influence of certain low-molecular substances on the melt-viscosity of polyethylene obtained at low pressure. When the low-molecular substances were added to the polyethylene, the fluidity of its melts showed a gradual increase or varied with the appearance of a minimum or a maximum. The anomalous changes in the viscosity depend on the composition and structure of the low-molecular additives and were observed at concentration of the order of 0.1 to 0.5 wt.-%. The substances which cause this effect were called viscosigenes. The influence of the viscosigenes on the viscosity is explained by the assumption that the macromolecules form long-existing aggregations in the polymer melts. The viscosigenes can be usd to extend the production capacities of polymer-processing units.     

Die Wärmekapazität von vollständig kristallinen Copolymeren des Polyoxymethylens

The molar heat capacity of fully crystalline copolymers of trioxane and 1,3-dioxolane can be discribed by the equation C_p(x₂, T) = 36,75 + 0,1425 (t₂ ? 25) + 80 x₂ in the temperature range 25°C < t < 140°C and at mole fraction of oxyethylene units x₂ < 0,16. For x₂ < 0,1 the molar heat capacity depends linearly on the reduced temperature T/T_m(x₂), but is independent from counit content.     

Über ternäre azeotrope — zur frage der existenz eines ternären azeotroppunktes ohne binäres azeotrop

The terpolymerization equations of Alfrey-Goldfinger and Ring for calculation of ternary azeotropes are compared. It is shown that the equation of Alfrey and Goldfinger can be transformed into that of Ring. Possible copolymerization ratios for the existence of ternary azeotropes without a binary one are discussed. Copolymerization ratios taken from literature show that there is a chance to find such and azeotrope, but and existing example was not found. So copolymerization ratios were arbitrarily chosen to give a range wherein such and azeotrope could exist.     

Über poly[1-N-(4-isothiocyanatophenyl)carbamoyloxy-methyläthylen-co-1-hydroxymethyläthylen]e als träger zur immobilisierung von papain

Poly[1-N-(4-isothiocyanatophenyl)carbamoyloxymethylethylene-co-1-hydroxymethylethylene]s ( 5a – c ) were obtained by reaction of poly(allyl alcohol) ( 2 ) with 4-isothiocyanatophenyl isocyanate ( 3 ). In some cases 1,4-phenylenediisocyanate ( 4 ) was used as crosslinking agent. These reactive carriers were found to be suitable to immobilize enzymes by covalent bonds. The binding abilities of these polymers 5a – e for butylamine, 3,4-dichloroaniline, peptone (from lactalbumin), and papain were investigated. The enzymatic activity, the pH-optimum, the apparent Michaelis-constant K_M(app), and the activity dependance on temperature were determined for the immobilized papain.     

Die chemische heterogenität von copolymerisaten. 4. Experimentelle untersuchungen zur verträglichkeit

Two chemically homogeneous methyl methacrylate/butyl acrylate copolymers form optically homogeneous (i.e. clear) mixtures in bulk only if the difference in their methyl methacrylate content does not exceed 10–20 mole-%. As torsional vibration experiments show, the mechanical homogeneity limit occurs at the same difference in the methyl methacrylate content. In inhomogeneous systems of two homogeneous copolymers these are found two corresponding damping maxima. Electron micrographs show the presence of structures of the order of magnitude of 30 Å even in some optically or mechanically homogeneous systems. The phase size increase suddenly near the turbidity limit. In mixtures of three components, the copolymer with a composition which lies in the middle does not aid compatibility. In copolymers with broad continuous chemical distributions microphases are formed from mutually compatible macromolecules. Optical and mechanical homogeneity or inhomogeneity is then a question of the size of the individual microphases. Suppression of transfer reactions in the polymer leads to an increase in the size of the microphases, while the size decreases when these reactions are encouraged. In agreement with this, graft copolymerization has a homogenizing effect. Preliminary experiments on copolymers of other monomers indicate that these observations are generally valid.     

Über die trennschärfe der gelchromatographie im vergleich zur fällungschromatographie

The dependence of the molecular weight of polypropylenglycols upon their elution volumes in various solvents is determined by gel permeation chromatography. The difference in the elution volumes of the polymer from one solvent to another solvent cannot be explained by the change in their coil dimensions. The basic parameters, such as the specific elution volume V_p and the change of the elution volume per degree of polymerization dV/dP are determined. The influence of those parameters on the separating efficiency in the gel permeation chromatography was investigated. The molecular weight distribution curve of a polypropylenglycol is determined both by the gel permeation chromatography and by the elution chromatography. The distribution curves and the average molecular weights obtained from both methods are in good agreement, especially when the dispersion coefficients of the components are taken into account. The inhomogeneity of the fractions obtained from both methods is calculated according to the equation given by SCHULZ et al. and determined by gel permeation chromatography. It shows that those fractions obtained by elution chromatography are slightly more homogeneous than those obtained by gel permeation chromatography.     

Polychalkone, 5 Untersuchungen über elektrische eigenschaften wärmebeständiger polychalkone

The present paper deals with the temperature dependence of electrical semiconductivity of pellets of the polychalcones 1a-c and 2a,b . It is shown that the electrical properties after heat treatment in air and under vacuum are reproducible and that the conductivity increases with increasing temperature indicating that the studied compounds are semiconductors. The values obtained for the energy of activation (in the region of intrinsic conductivity) vary between 1,45–2,25 eV/mol. The close relation between the energy of activation and the chemical structure is discussed.     

Orthophosphorsäuremonoester-Phosphohydrolaseaktivität der repressiblen Pyrohosphat-Phosphohydrolase I von Candida utilis

Two enzymes splitting inorganic pyrophosphate (I and II) have been investigated in Candida utilis. The results indicate that only enzyme I (no considerable thermoinactivation — 10 min, 71 °C-, optimum near pH 2.5, enzyme strongly bound to the cell, high splitting rates in vivo, derepression under phosphate starvation conditions) is also able to split orthophosphoric monoesters. Thus, the enzyme I is an unspecific acid orthophosphoric monoester phosphohydrolase (E. C. 3.1.3.2.).