Studies on the polymerization of ethyl acrylate. I. Kinetic studies

Kinetic studies on the polymerization of ethyl acrylate have been carried out and the various rate constants and their corresponding activation energies determined.     

Studies on the polymerization of ethyl acrylate. III. Effect of temperature on the solvent-transfer reaction

The effect of temperature on transfer constants for different solvents in the polymerization of ethyl acrylate was observed. Activation energy differences (E_trS ? E_p) and frequency factors were computed. It is observed that high frequency factors are associated with high activation energies. Values of E_trS were calculated by an approximate method and were compared with the available data on methyl methacrylate, isobutyl methacrylate, and styrene.     

Photochemical polymerization of gaseous ethyl acrylate

Exposure of gaseous ethyl acrylate to ultraviolet radiation causes deposition of poly(ethyl acrylate) at a rate depending on a number of parameters, including the wave-length of the radiation, its intensity, and exposure time. The rate also depends upon the monomer pressure and the presence of contaminants, most notably moisture and oxygen.     

Kinetic studies on the n-alkyl acrylate polymerization

Kinetic studies on the polymerization of n-butyl acrylate and n-octadecyl acrylate in toluene at 70°C with benzoyl peroxide as initiator are reported. High monomer orders of 1.55 and 1.75 were obtained for n-butyl and n-octadecyl acrylates, respectively. Though the initiator order in butyl acrylate polymerization was 0.5, the octadecyl acrylate polymerization showed less than square root initiator order. The activation energy for the polymerization of both the acrylates was determined. Autoacceleration was found even at low conversions. The autoacceleration was influenced by both monomer and initiator concentration. Molecular weight data was presented in support of the gel effect. © 1992 John Wiley & Sons, Inc.     

Radical polymerization of ethyl acrylate with dead end polymerization conditions

The radical polymerization of ethyl acrylate (EA) with 4,4^′-azobis(4-cyanovaleric)acid as initiator was investigated in propionitrile at 363 K in order to obtain carboxy-telechelic oligo(ethyl acrylate). The results of functionality and molecular weights showed that a transfer reaction had occurred. A molecular weight study was performed in order to show the importance of transfer to solvent due to the high reactivity of the EA radical. Finally, the radical polymerization was investigated at very low temperature (253-273 K), using a redox system initiation. A behavior of dead end polymerization was observed but the activation energy of propagation for EA is still high and does not allow the synthesis of a telechelic oligomer.     

Kinetics of free radical polymerization—XXXI. Solvent effect on the polymerization rate of ethyl acrylate

The free radical polymerization of ethyl acrylate was investigated in benzene and dimethyl formamide solutions at 50°. The effects of initiator and monomer concentration were studied over a wide range. The overall rate of polymerization was proportional to (initiator concentration)^{$\text{1}\text{2}$} but not to the concentration of the monomer. We attempted to interpret this solvent effect on the basis of (i) the diffusion theory, (ii) the theory of charge transfer complexes and (iii) the theory of hot radicals. Our experimental results could only be explained quantitatively in terms of hot radicals.     

Tailor‐made poly(ethyl acrylate) by atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) of ethyl acrylate (EA) was carried out using different initiators, CuBr or CuCl as catalyst in combination with different ligands e.g., 2,2′‐bipyridine (bpy) and N,N,N′,N″N″‐pentamethyl diethylenetriamine (PMDETA). Use of PMDETA as ligand resulted in faster polymerization rate (95% conversion in 15 min) than those using bipyridine (～58% conversion in 10.5 h). This is due to the lower reduction potential of copper‐amine than that of copper‐bpy complex, resulting in higher rates of activation of dormant halides. Use of ethylene carbonate as solvent lead to faster polymerization rate and better control in polymerization when compared with p‐xylene as solvent. The reaction temperature had a positive effect on polymerization rate and the optimum reaction temperature was found to be 90 °C. An apparent enthalpy of activation of ～85 kJ/mol was determined for the ATRP of ethyl acrylate, corresponding to an enthalpy of equilibrium of ～64 kJ/mol. By judicious choice of the reaction parameters it was possible to tailor the end group of the final polymer. MALDI‐TOF‐MS analysis and the chain extension experiment of poly(ethyl acrylate) (PEA) prepared using bpy as ligand showed the presence of ? Br as the end group. On the contrary, when PMDETA was used as the ligand, the mass spectra analysis showed hydrogen terminated polymer as the major species towards the end of polymerization. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1661–1669, 2007     

Studies on diacetylenic vinyl compounds. VI. ESR studies on the polymerization of diacetylene containing acrylate and methacrylates

A number of diacetylene containing acrylate and methacrylates have been synthesized and the interaction between their propagating radicals and the diacetylene groups was studied by ESR spectroscopy. In the case of polymerization at 70°C using AIBN as an initiator, the propagating radicals of methacrylates are temporarily trapped with the diacetylenes with rapid exchange of the electron, thus showing strong signals of the propagating radicals. Gamma irradiation of the frozen state produces a blue color in samples, and the ESR signals were found to be those of uninteracted acrylate and methacrylates. From a comparison of spectral widths, there seems to exist an intramolecular interaction between the radicals and the diacetylene group at the frozen state. © 1992 John Wiley & Sons, Inc.     

Effect of a bi-unsaturated monomer on the emulsion polymerization of ethyl acrylate

The emulsion polymerization and copolymerization of ethyl acrylate with a bi-unsaturated comonomer (divinylbenzene, 1,6-hexamethylene diacrylate), present in small proportions, in the presence of anionic emulsifier sodium dodecyl sulfate have been kinetically investigated at 60°C under batch conditions by gas chromatograhy and gravimetric methods. The rate of polymerization in interval 2 was found to be proportional to the 0,37, 0,23, and 0,5 power of the emulsifier concentration for the system A (ethyl acrylate), the system B (ethyl acrylatedivinylbenzene), and the system C (ethyl acrylate/1,6-hexamethylene diacrylate). Divinylbenzene was found to decrease both the rate of polymerization and the polymer particle size. Addition of 1,6-hexamethylene diacrylate slightly increases both the rate of polymerization and the polymer particle size.     

Atom transfer radical polymerization of 2-methoxy ethyl acrylate and its block copolymerization with acrylonitrile

2-Methoxy ethyl acrylate (MEA), a functional monomer was homopolymerized using atom transfer radical polymerization (ATRP) technique with methyl 2-bromopropionate (MBP) as initiator and CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as catalyst system; polymerization was conducted in bulk at 60 °C and livingness was established by chain extension reaction. The kinetics as well as molecular weight distribution data indicated towards the controlled nature of polymerization. The initiator efficiency and the effect of initiator concentration on the rate of polymerization were investigated. The polymerization remained well-controlled even at low catalyst concentration of 10% relative to initiator. The influence of different solvents, viz. ethylene carbonate and toluene on the polymerization was investigated. End-group analysis for the determination of high degree of functionality of PMEA was determined with the help of ¹³C{¹H} NMR spectra. Chain extension experiment was conducted with PMEA macroinitiator for ATRP of acrylonitrile (AN) in ethylene carbonate at 70 °C using CuCl/bpy as catalyst system. The composition of individual blocks in PMEA-b-PAN copolymers was determined using ¹H NMR spectra.     

Nitroxide-mediated photo-controlled/living radical polymerization of ethyl acrylate

The nitroxide-mediated photo-controlled/living radical polymerization of ethyl acrylate was attained using (2RS,2′RS)-azobis(4-methoxy-2,4-dimethylvaleronitrile) as the initiator, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator, and (4-tert-butylphenyl)diphenylsulfonium triflate as the photo-acid generator. The photopolymerization was performed in acetonitrile at room temperature by irradiation with a high-pressure mercury lamp. The molecular weight distribution of the resulting polymer decreased as the monomer concentration decreased. It was confirmed that the polymerization was controlled on the basis of the linear correlations for the first-order time-conversion plots and the plots of the molecular weight vs. the reciprocal of the initial concentration of the initiator, although the conversion–molecular weight plots did not show a completely linear correlation. The block copolymerization with methyl methacrylate accompanied by no deactivation of the growing polymer chain end supported the livingness of the polymerization.     

Studies on addition polymerization in mixed solvent system. Part I. Chain transfer of water in polymerization of methyl methacrylate

The role of water as a chain-transfer agent in addition polymerization of methyl methacrylate and acrylamide in a mixed solvent system was studied. Water does not have any transfer with the growing polymer radical. The degree of polymerization is found to increase with increasing water concentration. This is probably due to a reduced termination rate resulting from coiling of the polymer chain in the presence of a nonsolvent like water.     

Calorimetric study of the kinetics of the bulk polymerization of ethyl acrylate

The bulk polymerization of ethyl acrylate using 1-1′-azobisisobutyronitrile as initiator at several temperatures has been studied by DTA. The order with respect to the monomer and the apparent activation energy of the polymerization process have been determined.     

Chain transfer and living functionalization of polymethacrylates by group transfer polymerization using ethyl 2-Phenyl-2-butenoate

A living functionalization method has been investigated for group transfer polymerization (GTP) of poly(alkyl methacrylates) using ethyl 2-phenyl-2-butenoate (EPB). The end-capping reactions of EPB to living trimethylsilyl ketene acetal-ended poly(methyl methacrylate) (PMMA) chain ends have been systematically studied and characterized by SEC, VPO, UV-visible spectrosocopy, ¹H and ¹³c NMR spectroscopy. The results of sequential monomer addition, varying stoichiometry and copolymerization indicate that EPB effects efficient chain end functionalization only at stoichiometric concentrations; chain transfer reactions (chain transfer constant = 0.4) occur with excess EPB and during copolymerization with MMA. Chain transfer reactions (chain transfer constant = 0.1) also occur when copolymerizing ethyl 2-methyl-2-butenoate with MMA.     

Chain transfer in ethylene polymerization

Chain transfer constants in the homogeneous free-radical polymerization of ethylene at 1360 atm. and 130°C. have been determined for over 50 compounds, including nearly 300 hydrocarbons. The effects of substitution, unsaturation, and ring strain in the transfer agent molecule on the reactivity of its C? H bonds in chain-transfer reactions with a polyethylene growing chain are analyzed. Qualitatively, these trends parallel those found for simple radicals attacking simple molecules. However, the principle that the reactivity of a compound is the sum of the reactivities of all reactive bonds, which is well established for simple radicals and transfer agents, is found not to be true in ethylene polymerization. It is postulated that the deviations from this principle are due to steric factors which become very important when the free radical is bulky. The transfer constants measured in ethylene polymerization are also compared with transfer constants in other systems. A strong correlation is found between the transfer constants in ethylene and published data on rates of abstraction of hydrogen atoms by methyl radicals.     

Chain transfer reaction in the polymerization of substituted acetylenes. II. Chain transfer reaction to trimethylvinylsilane in the polymerization of disubstituted acetylenes by MoCl5–n-Bu4Sn

The effect of various olefins as chain transfer agents was studied in the polymerization of 1-chloro-1-octyne, 1-chloro-2-phenylacetylene, 2-octyne, etc., catalyzed by MoCl₅–n-Bu₄Sn (1 : 1). Si-containing olefins, especially trimethylvinylsilane, greatly lowered the polymer molecular weight in the polymerization of the Cl-containing acetylenes, e.g., the M _n of poly(1-chloro-1-octyne) was 4.2 × 10⁵ without an olefin, whereas it decreased to 3.4 × 10⁴, i.e., below 1/10 in the presence of trimethylvinylsilane (1/2 equiv to monomer). In contrast, the molecular weight of poly(2-octyne) did not decrease that much, even with trimethylvinylsilane. The Cl-containing polyacetylenes obtained in the presence of trimethylvinylsilane as chain transfer agent possessed the trimethylsilyl group. Thus, the present study enables control of the molecular weight of substituted polyacetylenes by chain transfer, and further verifies the metal carbene mechanism for the polymerization of substituted acetylenes. © 1993 John Wiley & Sons, Inc.     

Fluorescence probes for polymerization reactions: Bulk polymerization of styrene,n-butyl methacrylate,ethyl methacrylate,and ethyl acrylate

Julolidine malononitrile 3 was used as a fluorescent probe for high-conversion (free-radical) bulk polymerization of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, ethyl acrylate, styrene, and the copolymerization of styrene/n-butyl methacrylate. The fluorescence of the probe increased gradually as polymer conversion increased. This was followed by an abrupt rise in fluorescence intensities by a factor of 3 to 40 depending on the polymer formed. Finally the fluorescence intensities leveled off as the polymer limiting conversion was reached. The polymerization region in which fluorescence intensity increases sharply seems to correspond to the increase of the rigidity of the medium at the glass transition. A correlation between the limiting quantum yield of fluorescence of the dye and the polymer glass transition T_g and expansion coefficient α was found. These results were interpreted in terms of rotation-dependent nonradiative decay which links the excited-state conformation to the rigidity of the medium.     

Evidence for chain transfer in the atom transfer radical polymerization of butyl acrylate

Poly(butyl acrylate) (PBuA) of high molecular weight was synthesized by atom transfer radical polymerization (ATRP) in ethyl acetate. Whereas for low molecular weight polymers, a linear increase of the number‐average molecular weight, M_n, versus conversion and narrow molecular weight distributions indicate the suppression of side reactions, a downward curvature in the plot of M_n versus conversion was observed for high molecular weights (M_n > 50 000). This effect is explained by chain transfer reactions, leading to branched polymers. GPC measurements with a viscosity detector give evidence for the branched structure of high molecular weight polymers obtained in ATRP. In addition, transfer to solvent or monomer is likely to occur.