The copolymerization of unsaturated carboxylic acids with styrene and an unsaturated tertiary amine in benzene

The copolymerization parameters of 2-acryloyoxybenzoic (AOB) and 2-methacryloyloxybenzoic (MOB) acids, methyl 2-methacryloyloxybenzoate (MMOB), and N-methyl-N-phenyl-2-aminoethyl methacrylate (MPAM) with styrene in benzene solution were determined and used in the calculation of the Alfrey-Price copolymerization constants e and Q for AOB, MOB, MMOB, and MPAM. Using e Q thus determined and the corresponding tabulated values for methacrylic acid (MAA), the copolymerization parameters of pairs AOB-MPAM, MOB-MPAM, MMOB-MPAM, and MAA-MPAM were calculated. They are compared with those determined by the copolymerization of these pairs in which the interaction of functional groups on comonomers plays a role.     

Copolymerization of unsaturated carboxylic acids with styrene and an unsaturated tertiary amine in dimethyl sulfoxide

The copolymerization parameters of N-methyl-N-phenyl-2-aminoethyl methacrylate (MPAM) and 2-acryloyloxybenzoic (AOB), 2-methacryloyloxybenzoic (MOB), and methacrylic acid (MAA) with styrene in DMSO solution at 50°C were determined and used in the calculation of the Alfrey-Price copolymerization constants e and Q for MPAM, AOB, MOB, and MAA. From the e and Q constants of the monomers thus determined, the copolymerization parameters of the pairs MPAM-AOB, MPAM-MOB, MPAM-MAA were calculated and compared with those determined by the copolymerization of the corresponding pairs in DMSO.     

Kinetics of polymerization of alkyl cyanoacrylates by tertiary amines and phosphines

A theory of the overall rates and molecular weights in slowly-initiated, non-terminated polymerizations is developed for cases of complex initiation of alkyl cyanoacrylates by tertiary amines. Results with butyl cyanoacrylate (BCA) in the solvent THF, and five different amines (chiefly pyridine and derivatives) show widely differing overall rates. The theory, with the aid of previously determined initiation rate constants, permits the same value for the propagation rate constant (k_p) to be derived in all cases, corroborated by values derived from the simpler overall kinetics of polymerisation initiated by Ph₃P. The rate constant k_p shows very slight temperature dependence, less than one order of magnitude between 20 and ?80°C.     

The influence of the H-bonded association of COOH groups on the copolymerization of unsaturated carboxylic acids

The monomer reactivity ratios of styrene with unsaturated acids—4-(acryloyloxy)phenylacetic acid, α-(methacryloyloxy)phenylacetic acid and 4-(methacryloyloxy)phenylacetic acid—and their alkyl esters were determined in acetone and acetic acid solutions. Due to the isolation of the COOH and COOR groups from the benzene ring owing of the CH₂ group the electron densities on the polymerizable CC double bonds of these acids, their H-dimers, the H-associates with the solvent and their alkyl esters are identical. In spite of this, however, in the copolymerization of styrene with unsaturated acids the rate of addition to the polymeric radical was fastest for the H-dimers of the acids, less fast for a mixture of H-dimers and H-associates “unsaturated acid-acetic acid”, and slowest for the acid esters. The preferential enrichment of the copolymer with the acid is explained through a bimolecular addition of the first C?C of the H-dimer to the polymeric radical and a faster “monomolecular” addition of the C?C of the second dimer acid unit associated with the polymeric radical. If however, there is some steric hindrance to an immediate radical propagation between the C?C of two acid units joined by H-bonds between the carboxyl groups, several elementary acts of bimolecular addition of the other comonomer molecules may take place between the addition of the first and the second dimer acid unit.     

Oxidation of tertiary amines with N-chloronylon 66

Oxidation of tertiary amines with N-chloronylon 66 (NCN) was investigated in several organic solvents. NCN was found to oxidize N,N-dimethylaniline (DMA) at room temperature to give N-methylaniline with 15–50% yield, depending on the solvents used. Oxidation of N,N-dimethylbenzylamine (DMBA) gave benzaldehyde with 15–30% yield and a small amount of N-methylbenzylamine. A mechanism was discussed. For comparison, N-chlorosuccinimide, a low molecular N-chloro-compound, was also used for oxidation of DMA and DMBA.     

Heterogeneous polymerization of L-alanine N-carboxy anhydride initiated by amines having primary and tertiary amino groups

Various amines such as aniline (A), N,N-diethyl-1,3-propanediamine (DPD), and pamino-N,N-diethylaniline (ADA), were used as initiators in the heterogeneous polymerization of L -alanine N-carboxy anhydride (L -alanine NCA), (4-methyl-2,5-dioxo-1-oxa-3-azacyclopentane). When ADA is used as initiator, the initiation reaction proceeds via normal amine initiation as for primary monoamines. On the other hand, in the polymerization initiated by DPD, the initiation reaction takes place from both the primary and tertiary amino groups of the initiator. In all systems, the propagation proceeds by nucleophilic attack of the amino groups of the growing chains on the C⁽⁵⁾ of the L -alanine NCA ring. The resultant polymers obtained in the case of the initiators A or ADA had wider molecular weight distributions than those from DPD-initiated polymerization. Oligomers and polymers obtained using DPD as initiator were in the form of β-and α-conformations, respectively. However, mixtures of both β-structure and α-helix were formed in the polymerization initiated by A or ADA. It is suggested that the number of the growing chain ends occluded in the precipitate is increasing in the following order with respect to the initiator used: DPD<A≈ADA. The morphologies of the resultant polymer crystals were in good agreement with the results from IR and X-ray analysis.     

Initiation processes in polymerizations of alkyl cyanoacrylates by tertiary amines: Inhibition by strong acids

Polymerizations of butyl and ethyl cyanoacrylates, in the solvent THF, initiated by pyridine and other tertiary amines, are inhibited by strong acids, which cause well-defined inhibition periods (t_i) proportional to the concentration of acid added, but irrespective of its nature. The temperature and monomer concentration dependence of t_i indicate that chain-initiation is a composite sequence involving two or three successive additions of monomer. A detailed theory is proposed and used to evaluate the composite initiation rate constants over the temperature range 20°C to ?80°C. The influence of steric factors on the initiation by pyridine, picolines and lutidine is exemplified and discussed.     

On the mechanism of polymerization of formaldehyde initiated by tertiary amines and phosphines. 3rd communication on macrozwitterions

Two mechanisms are feasible in the anionic polymerization of virtually anhydrous formaldehyde initiated by uncharged LEWIS -bases such as tertiary amines and phosphines: 1. Direct initiation with formation of macrozwitterions the conventional mechanism in which an impurity such as water or methylene glycol acts as a cocatalyst. The investigations were carried out mainly by end group analysis. With triethyl amine as initiator the cocatalysis mechanism is the only or, at least, the predominant mechanism (at 20°C in dimethyl formamide). Quaternary ammonium ions – if any – are present in concentrations much below the concentrations of anionic chain ends. The latter were determined by termination with ethyl iodide and determination of the ethyl end groups formed in this termination reaction. Any quaternary ammonium end groups should be quite stable as indicated by the investigation of model compounds and by the lack of decomposition products in the polymer. In contrast, with triphenyl phosphine and with phosphorous acid tris(dimethylamide) as initiators the zwitterion mechanism seems to be correct and phosphorous is chemically incorporated in the polymers.     

Cationic polymerization of methoxyallene with protonic acids

The cationic polymerization of methoxyallene (1) was carried out with some protonic acids at ?50°C in dichloromethane. Polymer yield and molecular weight increase with the degree of acidity of the protonic acid (CF₃CO₂H < CH₃SO₃H < CF₃SO₃H), whereas the remaining double bond content in the polymer decreases with the acidity of protonic acids. Consequently, to obtain a polymer with high molecular weight and high double bond content (i. e., low degree of side reactions), the polymerization of 1 with medium acidic CH₃SO₃H gives the best results. It gives a highly unsaturated polymer in moderate yield, which can not be obtained with Lewis acids such as BF₃OEt₂.     

Cationic polymerization of methoxyallene with Lewis acids

The cationic polymerization of methoxyallene ( 1 ) was carried out with some Lewis acids at ?50°C in dichloromethane. BF₃OEt₂ was found to be an effective catalyst for the cationic polymerization of 1 . From analyses of ¹H and ¹³C NMR spectra, the obtained polymers consist of units with the 1,2-double bond of 1 being opened, although the 2,3-double bond is consumed also to an amount of 24 to 43 mol-%. This decrease in 2,3-double bond content in the polymer may be attributed to intramolecular cyclization of the propagating cation and/or the intermolecular reaction of the propagating cation with polymer to produce a graft polymer. Moderately polar solvents such as dichloromethane proved to be best suited for obtaining polymers with high double bond content.     

Anionic polymerization of siloxanes. Mechanism of initiation with triorganosilanolates

The kinetics of initiation of the polymerization of 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane ( 2 ) with sodium phenyldimethylsilanolate 1a and two of its phenyl substituted derivatives was investigated as model reaction for studying the initiation and crosspropagation steps in anionic polymerization of cyclic siloxanes in non-polar media. A redistribution of siloxane units between living ends of the polymer and also between living end and initiator was demonstrated to occur commonly in the siloxane anionic polymerization system affecting the initiation and crosspropagation. However, the living silethylenesiloxane polymer system 3 showed no redistribution and the initiation, followed by the dissapearance of phenyldimethylsilanolate, showed a first internal order and a fractional external order with respect to the initiator. The same fractional order was found in the propagation step with respect to the living ends. The results can be rationalized on the basis of a mechanism in which silanolate groups aggregation (cyclic or cage structures) convert active species into dormant centres. The analysis of the kinetic scheme including the formation of simple and mixed aggregate series of optional multiplicity leads to the conclusion that the scheme under some assumptions suits the kinetics observed. Solvation processes as well as the increase of the negative charge density on the silanolate oxygen by electron releasing substituents increase the reactivity of the silanolate.     

New aspects of the initiation mechanism of cationic polymerization catalyzed by proton acids and by friedel-crafts halides

In the polymerization of isobutene catalyzed by aluminium tribromide and in the polymerization of styrene catalyzed by trifluoromethanesulphonic acid it is supposed that an inactive catalyst monomer complex is formed which is in equilibrium with other active species. The monomer complexation of the catalyst explains the S-shaped conversion curves and the complex kinetics of the polymerization. The value of the equilibrium constant K_m (complexation constant) expresses what part of the catalyst may take part in the polymerization process as an active initiating species. For the system isobutene/AlBr₃, K_m was found to be 0,62 1/mol. In the system styrene/CF₃SO₃H, the high value of the complexation constant (K_m=23,0 1/mol) confirms that the main part of the catalyst is bound to the monomer to give an inactive complex. A general reaction scheme in which the catalyst is present in the form of neutral molecules, ion-pairs, and free ions is proposed which is applicable to most types of catalyst systems. Through shifting of equilibria between these different active species and through monomer complexation of neutral catalyst molecules one can explain the different course of conversion curves in different solvents and the influence of temperature on the kinetic pattern for many cationically polymerizable systems.     

The polymerization of vinyl monomers with N-chlorosuccinimide in the presence of protic acids

The polymerization of vinyl monomers with N-chlorosuccinimide ( 1 ) in the presence of protic acids such as p-toluenesulfonic acid (PTS) was investigated. From the kinetic studies of the reaction of 1 with PTS and the polymerization of methyl methacrylate (MMA) with the above combined initiator system, it was found that the polymerization is initiated by a radical produced by a bimolecular reaction between 1 and PTS, and is terminated by a second order reaction. ESR investigations on the reaction mixture of 1 with PTS by spin trapping technique clearly showed that the initiating radical is the N-succinimidyl radical. This radical results from a homolysis of the N? Cl bond of the protonated N-chlorosuccinimide 2 .     

Temperature requirements for initiation of RNA-dependent RNA polymerization

To continue the molecular characterization of RNA-dependent RNA polymerases of dsRNA bacteriophages (Cystoviridae), we purified and biochemically characterized the wild-type (wt) and a temperature-sensitive (ts) point mutant of the polymerase subunit (Pol) from bacteriophage phi12. Interestingly, initiation by both wt and the ts phi12 Pol was notably more sensitive to increased temperatures than the elongation step, the absolute value of the nonpermissive temperature being lower for the ts enzyme. Experiments with the Pol subunit of related cystovirus phi6 revealed a similar differential sensitivity of the initiation and elongation steps. This is consistent with the previous result showing that de novo initiation by RdRp from dengue virus is inhibited at elevated temperatures, whereas the elongation phase is relatively thermostable. Overall, these data suggest that de novo RNA-dependent RNA synthesis in many viral systems includes a specialized thermolabile state of the RdRp initiation complex.     

Cationic polymerization of isobutylene proceeding by redox initiation

The cationic polymerization of isobutylene with weak Lewis acids, such as BBr₃ and FeBr₃, has been studied. These halides are unable to induce individually the polymerization in nonpolar solvents, such as heptane or toluene, or they only initiate the polymerization to low conversions in polar media, such as dichloromethane. The complex compounds, formed by interaction of both Lewis acids, initiate a fast polymerization of isobutylene, which proceeds up to high conversions. The coinitiation effect of HBr in the mixture with BBr₃ and FeBr₃ was also investigated. The hypothetic formation of efficient initiators and the initiation mechanism of olefin polymerization are discussed on the basis of the ionogenic action of both Lewis acids.