Polymerization of methyl methacrylate with a benzoic anhydride/pyridine N-oxide system. Vinyl polymerization. 1221

The polymerization of methyl methacrylate was carried out in benzene, using benzoic anhydride/pyridine N-oxide system as initiator. As well as the results obtained in the case of benzoic anhydride/dimethylaniline N-oxide system, it was found that the rate of polymerization was proportional to the square roots of the initial concentrations of benzoic anhydride and pyridine N-oxide respectively, that the polymerization was remarkably accelerated in the presence of alcohols, and that hydroquinone inhibited the polymerization. From these results together with the observation on the composition curve of the copolymerization of methyl methacrylate with styrene, it was concluded that the system could initiate radical polymerization. The mechanism as for the radical formation was briefly discussed.     

Triphenylphosphine catalyzed polymerization of maleic anhydride

The polymerization of maleic anhydride initiated by triphenylphosphine was investigated in acetic anhydride as well as in dimethylformamide. It was found that the polymer conversion increases with the increase of the concentration of monomer and initiator and the reaction temperature. It was also found that the rate of polymerization is higher in dimethylformamide than in acetic anhydride under the same set of experimental conditions. The apparent overall activation energy was found to be about 26,4kJ · mol^-1 and 39,8 kJ · mol^-1 in acetic anhydride and dimethylformamide, respectively. The polymerization rate depends upon the basicity of the initiator as well as on the dielectric constant of the solvent.     

Mechanismus der NCA-Polymerisation, 3. Über die Amin katalysierte Polymerisation von Sarkosin-NCA und -NTA

Sarcosine-NTA ( 6b ), a hitherto unknown and—contrary to sarcosine-NCA ( 6a )—distillable liquid, was prepared from N-ethoxythiocarbonyl sarcosine ( 8 ). The polymerization of the NCA 6a and the NTA 6b in pyridine leads to higher polymerization degrees P?_n than with other tertiary amines. The polysarcosine resulting from the NTA shows thereby always lower molecular weights than that resulting from the NCA. During the pyridine catalysed polymerization of the NTA, 1,4-dimethyl-2,5-dioxopiperazine ( 3a ) is formed as byproduct and its amount increases with decreasing monomer concentration. The polymerization of sarcosine-NCA with pyridine or γ-picoline shows the greatest increase of P?_n in the range from 90–100% conversion, whereas with triethylamine as catalyst P?_n decreases in this range. Various reaction mechanisms are discussed; in the case of pyridine catalysis, initiation and propagation via “zwitterions” is the most probable mechanism. The NCA 6a was also polymerized with tert-butylamine as initiator at various monomer/initiator-ratios. P?_n, of the resulting polysarcosine was measured by ¹H-NMR-spectroscopy and an (η_sp/c)/M?_n relationship was established.     

Grafting of styrene onto carbon fibers having pendant thiol groups

Carbon fibers containing thiol groups were produced by reacting carbon fiber oxidized by nitric acid, with excess thiirane. Then, graft polymerization with styrene was carried out in a sealed tube under nitrogen. The following order of initiating ability of the investigated initiators was found: di-tert-butyl peroxide > p-cumenyl hydroperoxide (CHPO) > dodecyl peroxide > benzoyl peroxide > 2,2′-azoisobutyronitrile. When CHPO was used as initiator, the rate of graft polymerization was maximum at [CHPO] = 0,01 mol/1. Chain transfer constant and grafting efficiency, both calculated from the equations of Fox and others, were compared with the experimental results.     

Study of the isothermal bulk polymerization of methyl methacrylate by differential scanning calorimetry

Course and kinetics of the isothermal bulk polymerization of methyl methacrylate were studied by differential scanning calorimetry. The initiator used was 2,2′-azoisobutyronitrile. The polymerization was investigated at temperatures between 70 and 90°C at constant initiator concentration, 5,2.10^?2 mol dm^?3. The heat of polymerization at 70°C is ?52,3 kJ/mol (?12,5 kcal/mol) and decreases, i.e. becomes more negative, with increasing temperature. Initial rate constants for the polymerization were also determined and from them the overall activation energy, 77 kJ/mol (18,4 kcal/mol), which is in good agreement with the literature value. Another series of polymerization experiments were performed at 80°C with variable amounts of the initiator. The heat of polymerization found is ?52,8 kJ/mol (?12,6 kcal/mol) and depends only slightly on the initiator concentration. The overall rate of polymerization at low degrees of conversion depends on the square root of the initiator concentration. These findings thus corroborate the conclusion reached by other authors that differential scanning calorimetry is a useful method for studying the kinetics of polymerization.     

Vinyl polymerization by a cobalt complex

The rate of decomposition of the complex, sodium bis(diethanolamine)cobaltate octahydrate was studied at pH 7 and pH 1,6, respectively. This complex was found to initiate the vinyl polymerization (polymerization of acrylamide and methacrylamide) at pH 1,6 in aqueous medium. There was no polymerization at pH > 4. The dependences of the rate of polymerization on monomer concentration, initiator concentration, temperature, and pH were studied. The overall activation energy of the polymerization reaction was calculated. A kinetic reaction scheme is proposed on the basis of the experimental data.     

Study of the isothermal bulk polymerization of vinyl acetate by differential scanning calorimetry

The course and kinetics of the isothermal bulk polymerization of vinyl acetate were studied by differential scanning calorimetry. The initiator used was 2,2′-azoisobutyronitrile. The polymerization was investigated at temperatures between 55 and 70°C at constant initiator concentration, 5,0.10^?2 mol/l. The heat of polymerization at 60°C is – 19,5 kcal/mol and decreases with increasing temperature. Initial rate constants for the polymerization were also determined and from them the overall activation energy, 21,6 kcal/mol. Another series of polymerization experiments were performed at 60°C with variable amounts of the initiator. The overall rate of polymerization at low degrees of conversion depends on the square root of the initiator concentration which is in agreement with the assumed kinetic scheme.     

Die kationische polymerisation von monomerem formaldehyd in lösung. 39. Mitt. über polyoxymethylene

The heterogeneous cationic polymerization of dissolved formaldehyde was investigated between ?30 and ?78°C using various initiators and solvents. The rate of polymerization is first order with respect to monomer and initiator. In toluene at ?78°C the reactivity of the initiators decreases in the following order: SnCl₄ > CH₃COClO₄ > HClO₄ > AlBr₃ > BF₃?O(C₂H₅)₂ > TiCl₄ > FeCl₃ > SbCl₅ > H₂SO₄ > Cl₃CCOOH > HCOOH > I₂. The overall activation energies are in the range 1.0 to 10 kcal/mole. In most systems the degrees of polymerization (viscosity average P_v) increase roughly proportionally with monomer concentration and with conversion. Values up to P_v ～ 15,000 have been reached. Upon variation of the solvent the rates of polymerization increased and P_v decreased in the following order: n-pentane, toluene, diethyl ether, nitroethane, rnethylene dichloride, tetrahydrofuran, acetone. The low degrees of polymerization obtained in tetrahydrofuran and in acetone are due to chain transfer. Small concentrations of added water, methanol, formic acid, acetone or acetic anhydride apparently act as cocatalysts and accelerate the polymerization. In higher concentrations, however, they cause retardation and chain transfer. In many systems a drastic decrease in the rate of polymerization or complete stand-still was observed even after small conversions. This can be diminished or delayed by the above-mentioned polar additives or by using more polar solvents. In order to find the reason for this decrease in the rate of polymerization, the concentration of active cationic chain ends was determined by terminating the polymerization with a large excess of added amyl alcohol. The amyloxy endgroups formed in this termination reaction are determined by acid hydrolysis of the isolated and purified polymer and by gas chromatography of the amyl alcohol formed from the endgroups. In many systems this method led to the conclusion that initiation is fast and complete while propagation is increasingly inhibited by diffusion of monomer to the active centres occluded in the solid polymer. No indications of a genuine kinetic termination have been found.     

Study on the cationic polymerization mechanism of 1,3-dioxepane in the presence of ethylene glycol

The cationic polymerization of 1,3-dioxepane (DOP) initiated with trifluoromethanesulfonic acid (I) in the presence of ethylene glycol (EG) was investigated. At sufficiently low concentration of the initiator ([I] > 0.01 mol/L vs. [EG] < 0.20 mol/L), the molecular weights of the obtained polyacetal oligodiols are controlled by the mole ratio of consumed DOP to initial EG. Gel-permeation chromatography studies revealed that the concentration of cyclic oligomers in the products are negligible. The mechanism of the polymerization was investigated by means of kinetic studies. The results showed that the polymerization proceeds according to the active chain end mechanism (ACF) in combination with the activated monomer mechanism (AM); thus the cyclic oligomer in the obtained polymer is reduced, and intermolecular chain transfer to EG in ACE is dominant. It was also demonstrated that as [DOP]²[I]/[EG] decreases the contribution of ACE to the polymerization decreases and that of AM increases. In addition, ¹H and ¹³C NMR data illustrated that each macromolecule of polyDOP oligodiols contained one EG unit on average and that no EG end groups exist.     

Kinetics of nitrogen dioxide initiated polymerization of acrylamide

The polymerization of acrylamide initiated by NO₂ in DMF was investigated. The initial rate of the polymerization increases with the first power of the monomer concentration and a half power of the initiator concentration. The overall activation energy of the polymerization was determined to be about 20 kcal/mol (84 kJ/mol). The copolymerization of acrylamide was also carried out with MMA in a solution of NO₂ in DMF. The copolymer was found to be enriched in MMA content. The polymerization appeared to be initiated by free radicals.     

Study of the isothermal bulk polymerization of diallyl fumarate and related compounds by differential scanning calorimetry

Course and kinetics of the isothermal bulk polymerization of diallyl fumarate and the course of the polymerization of diallyl fumarate, diallyl maleate, and diallyl succinate by programmed heating were studied. 2,2′-Azoisobutyronitrile was used as initiator. The isothermal bulk polymerization was investigated at temperatures between 75 and 96°C and initiator concentrations ranging from 22,5 to 62,5 mmol/dm³ were applied. The bulk polymerization by programmed heating was investigated at temperatures between 40 and 190°C and at constant initiator concentration of 62,5 mmol/dm³. The negative value of the heat of isothermal bulk polymerization of diallyl fumarate at 75°C at the initiator concentration of 22,5 mmol/dm³ was found to be ?63,6 kJ/mol and to increase with increasing temperature to ?87,9 kJ/mol at 96°C. Also an increase was observed at higher initiator concentrations in the same temperature range. The initial rate constants for the isothermal bulk polymerization of diallyl fumarate were determined and from them the overall activation energy (100,4 kJ mol). It was found that the overall rate of polymerization at low degrees of conversion depends on the square root of the initiator concentration. The heats of the polymerization by programmed heating at constant initiator concentrations for diallyl fumarate, diallyl maleate, and diallyl succinate were found to be ?126,4, ?82,9, and ?90,8 kJ/mol, respectively. In all cases the DSC-curves display two peaks. On the basis of the results obtained, it was possible to interpret the differences in reactivity of individual functional groups in these compounds observed in programmed heating.     

The thiol/dimethyl sulfoxide system as initiator of polymerization in benzene medium, 2. Kinetic studies

The kinetics of butanethiol/dimethylsulfoxide (DMSO) initiated polymerization of methyl methacrylate in benzene medium was studied gravimetrically. The thiol acts as the reducing component of the initiator system and also as a transfer agent. The order with respect to [Butanethiol] is 0,48. In the lower concentration region between 4,69.10^?4 and 9,38.10^?2mol 1^?1, DMSO behaves simply as the oxidant of the initiator system, and the rate of polymerization has the usual square root dependence on [DMSO]. But above the concentration of 9,38.10^?2mol 1^?1 and up to 1,40mol 1^?1, DMSO acts both as an oxidizing agent and as a retarder, forming an adduct with the growing radicals, which propagates the reaction with a retarded rate. The order with respect to monomer concentration is 1,04, when DMSO is used in the lower concentration range and it increases to 1,25 when [DMSO] is higher than 9,38.10^?2mol 1^?1. Thiols of different structures affect the rate significantly. The rate of polymerization is also dependent on the polarity and viscosity of the solvent being a maximum in benzene and a minimum in ethyl acetate. The efficiency of initiation of the initiator system is 60–80% and the overall activation energy is 72,45 kJ mol^?1. An appropriate kinetic expression was derived to explain the results.     

On the mechanism of anionic polymerization of maleic anhydride, 2

The triphenyl and tributyl phosphine initiated polymerization of maleic anhydride was investigated. The structure of the macro zwitterions, formed under the given reaction conditions, depended on the initiator employed. If the polymerization was initiated by triphenyl phosphine, the macromolecules contained succinic anhydride units and cyclopentanone derivatives, formed from further rearrangement. If, however, tributyl phosphine was employed as initiator, the polymers were mostly made up of conjugated ketoolefinic units. IR, NMR and mass spectrometric measurements were carried out to determine the structure of the polymers. Existence of the macro zwitterions was proved by high voltage electrophoresis. The semi-conductor properties of the polymers containing conjugated ketoolefinic units are discussed. Spectroscopic investigation of the kinetics of the triphenyl phosphine initiated polymerization of maleic anhydride showed that the initiation reaction of the ylide, formed with the monomer, proceeded about 90 times slower than the propagation reaction due to addition of the monomer to the growing chain-end.     

Emulsion copolymerization of methyl methacrylate with ethyl acrylate, 1. Effect of the initiator concentration on the polymerization behaviour

The emulsion copolymerization of methyl methacrylate with ethyl acrylate, initiated by ammonium persulfate in the presence of both anionic and nonionic emulsifiers, was kinetically investigated at 60°C by the conventional gravimetric method. In the range of low conversions the rate of polymerization was found to be proportional to the 0,5 power of the initiator concentration. Over the range of medium conversions the rate of polymerization is approximately proportional to the 0,35 power of the initiator concentration and the number-average molecular weight is inversely proportional to the 0,4 power of the initiator concentration. The molecular weight increases up to 30% conversion and then it remains constant up to the total monomer consumption. It was found that the mean particle diameter decreases while the number of particles per volume unit, the conductivity of final latices, the coagulate yield and the number of radicals per particle increase with increasing concentration of the initiator.     

Estimation of the rate constant of termination by the monomer in the anionic polymerization of methyl methacrylate

Based on the assumption that the termination reaction in the anionic polymerization of methyl methacrylate in THF with cumyl cesium as initiator is exclusively caused by the monomer, the termination rate constant k_t(±) for the ion-pairs of polymethylmethacrylcesium is estimated by analyzing the molecular weight distribution (MWD) of polymer samples prepared at different temperatures under otherwise identical reaction conditions. The activation energy of the termination reaction of the ion-pairs is found to be about 11 kcal/mol (46 kJ/mol). – The relatively broad MWD of the non-deactivated chains (the so called internal nonuniformity) reveals the existence of ion-pairs with different reactivity.     

Caesium as counter-ion in the anionic polymerization of ethylene oxide, 3. Dimethyl sulfoxide as solvent

The anionic polymerization of ethylene oxide in dimethyl sulfoxide using the caesium 3,6-dioxa-1-octanolate as initiator was studied at 50°C. Conductivity measurements have shown that the living polymer exists as free ion or contact ion pair. The reaction rates were found to be first order with respect to monomer and 1,9 order with respect to initiator with a mean value for the propagation rate constant of 60 mol ^{?1, 9}l^{1, 9}s^?1. Based on the experimental findings a polymerization mechanism is proposed.     

Biological activities of new poly(N 1-adamantylmaleimide) and poly(N-1-diamantylmaleimide)

N-1-Diamantylmaleimide was synthesized by reaction of maleic anhydride with 1-aminodiamantane, followed by dehydration with acetic anhydride and sodium acetate. Poly(N-1-adamantylmaleimide) (Ila) and poly(N-I-diamantylmaleimide) (IIb) were sythesized by free radical polymerization. N-1-Adamanlylmaleimide (Ia) and N-1-diamantylmaleimide (1b), exhibited strong activities in vitro antitumor activities. Interestingly, poly(N-1-adamantylmaleimide) exhibited growth inhibitory values against Colo 205, Hep G2, and SK-BR-3, similar to 5-Fluorouracil. It was noted that poly(N-1-adamantylmaleimide) showed relatively lower cytoxicity against Molt-4 cells than against Colo 205, Hep G2, and SK-BR-3 cells. The decreasing antitumor activities against individual tumor cell line were in the order Ia > Ib > IIa > IIb. This result shows that N-substituents of maleimides play an important role in their antitumor activity. Additionally, Ia and Ib show good in vitro activity against staphylococcus aureus ATCC 25923 while polymers IIa and IIb exhibited weak activity against S. aureus ATCC 25923.     

Vinyl polymerization. 235. Free radicals in the polymerization of vinyl monomers initiated by GOMBERG's and its relatad reactions

Free radicals derived from the GOMBERG 's reaction of arylmethyl halides such as benzyldiphenylmethyl-, and tritylbromide and chloride, with silver powder or mercury can initiate the radical polymerization and copolymerization of styrene, methyl methacrylate, acrylonitrile, vinyl chloride, and vinyl acetate. The orders of initiating abilities of halides in the polymerization of styrene and methyl methacrylate were as follows; for bromides, benzyl- > diphenylmethyl- > trityl-, and for chlorides, diphenylmethyl- > benzyl- > trityl-, when silver was used as metal component, while the order for the both halides is diphenylmethyl- > benzyl- > trityl- with mercury. These results were understood by the competition of the reactivities of halides to metal with those of the derived radicals to monomer. The over-all polymerization rate of the system styrene/silver/benzyl bromide was proportional to monomer concentration, square root of halide concentration, and square root of the amount of added but insoluble silver powder. The radical-like composition curves of styrene-methyl methacrylate copolymers and the inhibition of polymerization by verdazyl, a stable free radical, show that these polymerization systems include radical propagation step. Hexaphenylethane and 1.1.2.2-tetraphenylethane were isolated from the reaction systems, trityl halide/silver and diphenylmethyl chloride/silver or mercury, respectively. Recombination products of verdazyl with diphenylmethyl radical and benzyl radical were also isolated, but not N-trityl-verdazyl. Tracer study with benzyl bromide-7?¹⁴C showed the incorporation of benzyl fragments in the obtained polymer.     

Polymerization of vinyl acetate with 1,1′-diacetoxy-1,1′-diphenylazoethane

The kinetic and thermal parameters for the decomposition of 1,1′-diacetoxy-1,1′-diphenylazoethane were determined using differential scanning calorimetry (DSC). The activation energy for decomposition is 145,1 kJ/mol, the heat of decomposition is ?231,6 kJ/mol, and the rate constant (k_d in s^?1) obeys the relation in k_d = 40,43 ? (17460 K/T). This compound was used as initiator for the bulk polymerization of vinyl acetate. The polymerization was studied at 50, 55, 60, and 65°C. The rate of polymerization was followed dilatometrically. The per cent shrinkage was calculated from the partial specific volumes of polyvinyl acetate in vinyl acetate. The partial specific volumes were determined by means of an automatic digital densimeter. The number average of polymerization was obtained from viscosity data. The reaction order with respect to initiator concentration is smaller than 0,5 (between 0,27 and 0,31). The deviation is explained in terms of primary radical termination. The bulk polymerization of vinyl acetate at 65°C using both 1,1′-diacetoxy-1,1′-diphenylazoethane and 2,2′-azodiisobutyronitrile as initiators was also investigated by DSC technique. The data were used for obtaining various kinetic parameters.     

Kinetics of the aqueous polymerization of acrylamide initiated by the permanganate- tartaric acid redox system

The kinetics of the aqueous polymerization of acrylamide, initiated by the permanganate/tartaric acid redox system was studied at 35±0,2°C under nitrogen. The initial rate of polymerization remains independent of the tartaric acid concentration in the range 3,3.10^—3 to 9,9.10^—3mol/dm³. The order of the reaction with respect to the catalyst concentration (catalyst exponent) is found to be 0,55, indicating a bimolecular mechanism for the termination reaction. The rate of polymerization varies linearly at low monomer concentrations (1,25.10^—2 to 5,0.10^—2mol/dm³). With increase in temperature above 35°C, the initial rate increases but the conversion decreases. The overall energy of activation is found to be 18,68 kcal/mol (78,10kJ/mol) in the temperature range 30 to 50°C. Water miscible organic solvents and neutral salts depress both the rate and the conversion. Addition of MnSO₄ or the injection of more catalyst at intermediate stages raises both the initial rate and the maximum conversion. NaF decreases the rate but increases the conversion.