Zur polymerisation und copolymerisation von α-methoxystyrol

α-Methoxysyrene cannot be homopolymerised, neither by an anionic nor by a cationic or free radical mecanism. This monomer is more reactive in the cationic copolymerisation than vinyl ethyl ether. Its incapability to form longer sequences indicates a low ceiling temperature. In the free radical copolymerisation with styrene, acrylonitrile, methacrylate and methyl methacrylate (MMA) the parameter for α-methoxystyrene is always found to be zero. From the parameters of the first three comonomers the Q-and e-values are estimated to Q = 0.65 and e = -1.20. The relatively low Q-value and very low reactivity towards poly (MMA radicals) demonstrate the occurance of considerable steric hindrance during polymerisations with α-methoxystyrene.     

Zur anionischen copolymerisation von α-methylstyrol und styrol

The reactivity ratios for anionic copolymerization of α-methylstyrene (M₁) and styrene (M₂) were determined. The reactions were carried out in tetrahydrofuran solutions of varied monomer contents. The polymerization stops after complete styrene consumption since α-methylstyrene does not homopolymerize under the choosen conditions. From the residual monomer contents the reactivity ratios can be computed by means of the integrated copolymerization equation, yielding r₁ = 0.015, r₂ = 17 (25°C); r₁ = 0.024, r₂ = 28 (0°C); r₁ = 0.029, r₂ = 43 (?20°C). Due to the large difference of the r-values, the monomer ratio is considerably shifted during copolymerization. Therefore, all polymer molecules, since growing over the whole conversion range, show identical structure but a shift of composition along the chain. For this phenomenon the term “second order chemical heterogeneity” is suggested.     

Zur copolymerisation von ethylen und α-olefinen mit ziegler-katalysatoren

Starting with four reaction equations which are at least necessary to describe the copolymerization of two monomers, equations for the kinetics and the molecular weight regulation with and without hydrogen are derived. The equations are used to evaluate the results of the copolymerization of ethylene and 1-butene. The numerical values of the reactivity ratios r differ by approximately 3 orders of magnitude, but do not depend on whether the molecular weight is regulated by hydrogen or not. The rate of polymerization is scarcely influenced even by great amounts of 1-butene. It depends nearly completely on the concentration of ethylene. On the other hand the comonomer enormously influences the average molecular weight of the copolymer. This influence increases with hydrogen content.     

Zur copolymerisation von α-methylstyrol und butadien III. Das NMR-spektrum der sequenzen mit zentraler α-methylstyroleinheit

220 MHz proton resonance spectra of copolymers from α-methylstyrene and butadiene have been investigated. Model compounds have been prepared by a lithiumbutyl initiated copolymerisation in tetrahydrofurane at ?75°C. The NMR spectra of the phenyl and α-methyl group are interpreted by signals from configurational and compositional triads with a central χ-methylstyrene unit. The chemical shift of the triads, possessing a central α-methyl styrene unit, takes place to lower field in the α-methyl region to such an extend that no strong overlapping with the signals of the configurational triads takes place. In the region of the phenyl protons configurational and compositional triads are overlapping each other. Using 3,4,5-trideuterio-α-methylstyrene it is possible to assign configurational and compositional triads in the resonance spectrum of the ortho-phenylprotons.     

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.     

Kinetik der radikalischen copolymerisation α-substituierter styrole mit styrol. 3. Teil. Das zusammenwirken von copolymerisation,retardierung und kettenübertragung in abhängigkeit von der chemischen struktur

The copolymerization of styrene with a series of ten α-substituted styrenes, partially synthesized for the first time, was investigated by kinetic measurements. All compounds react with styrene according to the mechanism of copolymerization. The extent of the observed retardation or chain transfer reaction depends on the chemical nature of the α-substituent. Some α-alkylstyrenes scarcely show chain transfer, yet the more bulky the α-substituent is, the more retardation could be observed. On the other hand α-arylalkylstyrenes of the type of 4-substituted 2.4-diphenyl-1-butene-derivates cause an evident chain transfer as can be seen from the chain transfer constants of 0,29 and 0,26 from 4-methyl-2.4-diphenyl-1-pentene and 2.4.4-triphenyl-1-pentene, respectively. The single rate constants of chain propagation and chain transfer are calculated or estimated.     

Kinetik der radikalischen copolymerisation α-substituierter styrole mit styrol. 1. Teil. Copolymerisation von α-methylstyrol mit styrol oberhalb der ceiling-temperatur von α-methylstyrol

The radical copolymerization of α-methylstyrene with styrene in the temperature range from 60 to 150°C can be described according to the equations derived by WITTMER with the assumption, that the addition steps of α-methylstyrene may be reversibel. For the temperature range from 60 to 110°C it could be demonstrated that it would be sufficient to consider only the reversibility of the addition steps of α-methylstyrene to a radical end with α-methylstyrene as the terminal unit. At a reaction temperature of 150°C the addition of α-methylstyrene to a styryl chain end is also reversible, the equilibrium constant being only 1/30 of the α-methylstyrene homopolymerization. The retardation of the polymerization rate by admixture of small amounts of α-methylstyrene to styrene was measured. The results allow an estimation of the rate constants and activation energies of the chain propagation and depolymerization steps.     

Copolymerisation von Acrylnitril und α-Chloracrylsäuremethylester

The kinetics of the emulsion copolymerization of acrylonitrile and methyl α-chloro-acrylate were studied. Conversion, intrinsic viscosity, density, differential composition of the products and induction period were determined. Probability functions for the distribution of acrylonitrile and methyl α-chloro-acrylate chain segments were calculated. Macromolecules from these two monomers were shown to consist of randomly arranged short chain segments. It was shown that the degree of conversion is directly proportional to the square root of the concentration of methyl α-chloro-acrylate. The induction period decreases as the methyl α-chloro-acrylate concentration increases. The degree of conversion depends on the pH of the reaction medium. At a pH > 7 the reaction is markedly restrained.     

Die stereoregulierte homo- und copolymerisation des butadiens

The preparation of homopolymers of butadiene in the presence of cobalt and vanadium-containing ZIEGLER -catalysts is reported and the influence of water on the reaction system is investigated. Furthermore, the preparation of copolymers of butadiene with isoprene, 1,3-pentadiene, and styrene in the presence of the catalysts is described and the technical properties of the polymers discussed. While, the homopolymers have a sterically uniform structure, butadiene is sterically less regularly introduced into the copolymers. Only in the case of containing catalysts, butadiene is homo- and co-polymerized in 1,4-trans position. Individual technical properties of the copolymers yet not the properties as a whole are superior to 1,4cis-polybutadiene.     

Die radikalische copolymerisation in 3-stellung substituierter acryl- und methacrylaldehyde mit styrol

Radical copolymerization of styrene (S) with crotonaldehyde (3-methylacrylaldehyde) ( 1a ), cinnamaldehyde ( 1b ), 2-methyl-3-phenylacrylaldehyde ( 1c ), 3-(2-furyl)acrylaldehyde ( 1b ), and 3-(2-furyl)-2-methylacrylaldehyde ( 1e ) was studied. Monomer reactivity ratios (r_1a = 0,45, r_S = 15,5; r_1b = 0,95, r_S = 2,9; r_1c = 0,04, r_S = 13,0) were estimated. It was found that the polymerization of the substituted aldehydes is influenced by steric hindrance and by transfer reactions, and the polymerization rate decreases even at low concentrations of furyl derivatives in the monomer feed. The aldehyde monomers undergo copolymerization as other vinylic monomers except 1e . In the copolymer of 1e with styrene conjugate double bonds (C?O and C?C) were found. The structure of the copolymers is further complicated owing to a possibility of forming pyrane rings arising from neighbouring aldehyde units by cyclisation. The IR data are in good agreement with the statistical assumptions on the sequence length distribution of the monomeric units.     

Synthese von polyestern durch copolymerisation von dicarbonsäreanhydriden und ringäthern

Linear polyesters may be synthesized by copolymerization of dicarboxylic acid anhydrides and cyclic ethers according to anionic or cationic reaction mechanisms. Anionic copolymerization of dicarboxylic acid anhydrides and epoxides is catalyzed by salts of inorganic and organic acids, by alkalis, or amines. Reaction dependance from various experimental parameters was investigated. The polyesters are free from ether links and copolymerization runs strictly alternating. From experimental results a reaction mechanism for copolymerization of carboxylic acid anhydrides and epoxides was derived. Cationic copolymerization of dicarboxylic acid anhydrides with oxacyclic compounds such as five or higher membered cyclic ethers is catalyzed by complex cationic catalysts as LEWIS acid / cocatalyst or oxonium salts. The polyesters received partially contain ether links. Ether content varies with the molar ratio of monomers and especially with catalyst type and catalyst concentration. Polyesters partially containing ether or acetal links may also be prepared under the same conditions from polyethers or polyacetals and dicarboxylic acid anhydrides. Reaction mechanisms for the reactions investigated are suggested.     

Zur Copolymerisation von α-Methylstyrol und Butadien. IV. Die s0/M-Beziehung der Copolymeren

The sedimentation constants of poly-α-methylstyrene, polybutadiene and their copolymers have been measured in cyclohexane at 37°C. Depending on their composition block and random copolymers show the same sedimentation behavior. Within experimental error no influence of the sequence length distribution of the comonomers exists. The sedimentation constants of the copolymers may be calculated from the s₀/M-relations of the homopolymers.     

Kinetik der radikalischen polymerisation und copolymerisation von N-vinyl-N-methylacetamid

In order to get information on the kinetics of free radical polymerization of N-vinyl-N-methylacetamide (VIMA) polymerizations of the purified monomer were performed in dilatometers using the temperature range from 25 to 70°C, monomer concentrations of 10 to 100% in methanol, and initiation either by γY-irradiation or by radical initiators. Molecular weight meassurements of the polymer were calibrated by light scattering determinations of M_w according to the following equation at 30 °C in methanol: [η]/(ml/g) = 5,02 · 10^?3 · M_w^0,7946. Normal kinetics of free radical polymerization were found to be valid and Arrhenius parameters were calculated for the ratio k_p²/k_t of the propagation rate constant k_p and the termination rate constant k_t as well as for the monomer transfer constant C_M and for the efficiency of initiation f. For copolymerizations of N-vinyl-N-methylacetamide with different comonomers the mean Q-e-values were calculated as follows: Q_VIMA ? 0,06; e_VIMA ? ? 1,8.     

Nachweis von α-Mannosidase und β-Glucosidase in einem für die Hefezellwand lytischen System von Streptomyces spec. 5s

Streptomyces spec. 5s accumulates in the culture fluid lytic activities against living cells of Candida guilliermondii H. From the culture fluid a freeze-dried dialyzed ammonium sulfate precipitate was prepared. Except β-glucosidase-activity it showed activity of α-mannosidase which was characterized. Separation of both enzymes by chromatography on polyacrylamide gel was possible.     

Homo- und copolymerisation von N,N-disubstituierten carbamoyloxyalkylacrylaten und -methacrylaten

Methacrylates and acrylates ( 3a–i ) of 2-hydroxyalkyl carbamates ( 2 ) were synthesized and radically homo- and copolymerized. It was found that the homopolymerization follows the usual kinetic laws. The physico-chemical properties of the polymers are determined by the bulky and polar side groups which was revealed by measurements of the viscosity, of GPC, of X-rays, of DTA, and of NMR. The behaviour of the methacrylates in the radical copolymerization with a series of comonomers is similar to that of methyl methacrylate. However, the tendency to incorporation of the new monomers into the copolymers is less than that of methyl methacrylate. This fact could be caused again by the different steric effects.     

Feldionen- und Elektronenstoß-Massenspektrometrie von Polymeren und Copolymeren, 3. Copolymere des α-Methylstyrols mit Methylmethacrylat und Acrylnitril

Pyro-field ion mass spectrometry was used to study the primary fragments as well as the depolymerization behaviour of some α-methylstyrene (α-MS) copolymers. α-MS-methyl methacrylate (MMA) copolymers, when pyrolyzed, decompose mainly into the two monomers. The zip-depolymerization usually proceeds through the whole chain, disregarding the hetero-links between different monomeric units. Hetero-fragments are formed only with a small probability; still lower is the concentration of homo-dimers in the pyrolysate. Primary fragments of poly(acrylonitrile) (PAN) are acrylonitrile (AN), (AN)₂, (AN)₃, HCN, C₃H₅CN, C₄H₇CN, C₅H₉CN and higher nitriles. During pyrolysis of α-MS-AN copolymers, α-MS sequences zipdepolymerize with formation of the monomer. This retropolymerization stops at heterolinks, and fragments of the type α-MS-AN or α-MS-(AN)₂ are formed. Long AN sequences in the copolymer cause, as PAN itself, formation of AN oligomeres as well as higher alkene cyanides. Isolated AN units lead to the formation of monomeric AN.