Reactivity ratios and monomer partitioning in the microemulsion copolymerization of vinyl acetate and butyl acrylate

The true monomer reactivity ratios for the vinyl acetate/butyl acrylate system were determined with experimental data from the cumulative copolymer composition at low, intermediate, and high conversions and with the monomer partitioning among the aqueous, microemulsion droplet, and polymer particle phases taken into account. A mixture of sodium dodecyl sulfate and poly(ethylene oxide) (23) dodecyl ether (Brij‐35; 3 : 1 w/w) was used as a stabilizer. Potassium persulfate was used as an initiator. The true values of the monomer reactivity ratios were 0.028 ± 3.2 × 10^?3 for vinyl acetate and 6.219 ± 3.1 × 10^?1 for butyl acrylate, and these were in agreement with those reported in the literature for bulk copolymerizations but differed from values reported for other compartmentalized copolymerizations. Thus, these results indicate that the monomer partitioning and cumulative copolymer composition throughout the reaction have to be duly accounted for in the determination of monomer reactivity ratios in heterogeneous polymerizations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Bulk copolymerization of dimethyl meta-isopropenyl benzyl isocyanate (TMI®): Determination of reactivity ratios

Dimethyl meta-isopropenyl benzyl isocyanate (TMI®) is a bifunctional monomer with an unsaturation and an isocyanate group. Bulk copolymerizations of TMI with styrene, methyl methacrylate, and n-butyl acrylate were investigated. Polymerizations were carried out to low conversions in sealed test tubes at 70°C. The copolymer composition was determined using Fourier transform infrared (FTIR) spectroscopy. The data were analyzed using the terminal, as well as restricted penultimate, model of copolymerization. The method of Kelen-Tudos was used to calculate the reactivity ratios according to the terminal model. A nonlinear regression analysis was also carried out. Low reactivity ratio values for TMI were obtained for the copolymerizations with styrene and methyl methacrylate as a result of the inability of TMI to undergo homopolymerization. The value was higher for the copolymerization with n-butyl acrylate. Composition diagrams were generated, and the range of TMI concentration in the monomer charge for the preferential incorporation of TMI in the copolymer was identified. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 559–568, 1998     

Azeotropy in terpolymerization of 2-pyrimidyl acrylamide with different alkyl acrylates and acrylonitrile

2-Pyrimidyl acrylamide monomer (2PA) has been prepared by the reaction of 2-amino pyrimidine with acrylolyl chloride in the presence of triethylamine as catalyst. Its structure was confirmed by IR and ¹H NMR spectroscopy. Ternary copolymerizations of 2-pyrimidyl acrylamide monomer (2PA) with methyl acrylate (MA), methyl methacrylate (MMA), ethyl acrylate (EA), butyl acrylate (BuA) and acrylonitrile (AN) were carried out in THF at 65°C in the presence of a free radical initiator. Experimental terpolymerization data agree well with calculations based on the Alfrey–Goldfinger equation. The determination of unitary, binary and ternary azeotropies of the various systems studied were easily handled by a computer. The ternary azeotropic compositions for 2PA–MA–AN and 2PA–MMA–AN were 32.20:17.5:50.30 and 13.54:52.64:33.82mol%, respectively. Pseudo-azeotropic regions were identified where the deviation between feed and polymer composition is very small.     

Conventional and RAFT miniemulsion copolymerizations of butyl methacrylate with fluoromethacrylate and monomer reactivity ratios

Reversible addition fragmentation chain transfer (RAFT) mediated and conventional miniemulsion copolymerizations of butyl methacrylate (BMA) with fluoromethacrylate (FMA) were carried out at 70°C with potassium persulphate as initiator. The kinetics of the copolymerizations was investigated comparatively. Copolymer compositions at low conversion levels were determined by ¹H NMR and FTIR spectra techniques. In the presence of RAFT agent 2‐cyanoprop‐2‐yl dithiobenzoate, the copolymerization of BMA with FMA in miniemulsion was obviously retarded. The copolymerization exhibited typical features of controlled molecular weights and narrow polydispersities. The reactivity ratios were evaluated by Kellen‐Tudos (K‐T) method, which yields the apparent reactivity ratios: r_BMA = 0.73 and r_FMA = 0.75 in conventional copolymerizations, and r_BMA = 0.65 and r_FMA = 0.70 in CPDB‐mediated system. The results show that the monomer FMA with a perfluoroalkyl side chain is slightly more reactive than BMA, and the copolymerizations process have a tendency to crosspropagate and to produce a higher FMA content in the copolymers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

An in-depth analytical approach to the mechanism of the RAFT process in acrylate free radical polymerizations via coupled size exclusion chromatography-electrospray ionization mass spectrometry (SEC-ESI-MS)

Coupled size exclusion chromatography (SEC)-electrospray ionization mass spectrometry (ESI-MS) was applied to carefully map the product spectrum of a series of acrylate free radical polymerizations mediated via the reversible addition fragmentation chain transfer (RAFT) process. The product stream of a significantly rate retarded RAFT system (i.e. n-butyl acrylate (BA)/cumyl dithiobenzoate (CDB)) was compared with the less rate retarded RAFT polymerizations of BA mediated by cumyl phenyl dithioacetate (CPDA) and methyl acrylate (MA)/CPDA. In each case excellent agreement between the theoretical and experimental masses, as well as the simulated isotopic peak distributions, of polymeric species in the product stream was observed. Although conventional disproportionation and combination bimolecular termination products were clearly identified within the product spectra, the presence of irreversibly terminated RAFT intermediates, i.e. 3-armed star polymers, was not observed. The mass spectroscopic results are compared to modeling estimations (carried out via the PREDICI^® program package) of the concentration ratios of 3-armed stars vs. conventional termination products. It is demonstrated that the occurrence of conventional termination products should be accompanied by a significant product stream associated with 3-armed star polymer material if cross termination was operational—at least under the current reaction conditions. The absence of three armed star polymer products in the polymers stream suggests that irreversible cross termination reactions may be of minor importance in the present systems.     

Copolymer composition control in emulsion polymerization using technical grade monomers

A method to determine the minimum time monomer addition policy for composition control in emulsion polymerization systems when technical grade monomers are used is presented. The method involves a series of semicontinuous emulsion copolymerizations carried out under semistarved conditions. The values of the propagation rate constants, reactivity ratios and monomer partition coefficients are required to use the approach. The method is model-independent and does not require extremely accurate measurements of the particle size. The method was checked in the methyl methacrylate-ethyl acrylate seeded emulsion copolymerization. The monomers contained 4-methoxyphenol as inhibitor. It was found that the iterative approach converged rapidly.     

Synthesis, characterization polymerization and antibacterial properties of novel thiophene substituted acrylamide

Ethyl 2-acrylamido-4,5,6,7-tetrahydrobenzo [b] thiophene-3-carboxylate (ETTCA) has been synthesized and its structure has been elucidated by elemental analysis and spectral tools. Free radical polymerization of (ETTCA) has been conducted in several solvents using azobisisobutyronitrile (AIBN) as an initiator. The kinetic parameters of polymerization of the ETTCA were investigated, and it was found that the polymerization reaction follows the conventional free radical scheme. The overall activation energy of polymerization ΔE was determined (ΔE = 45.11 kJ mol⁻¹). The copolymerization of ETTCA with three conventional monomers was carried out in dioxane at 65 °C. The monomer reactivity ratios for the copolymerization of ETTCA with methyl methacrylate (MMA), vinyl acetate (VA) and vinyl ether (VE) were calculated. Thermal stability of the ETTCA polymer and its copolymers were investigated by thermogravimetric analysis. It has been found that the prepared polymer (PETTCA) and its copolymers with VA have moderate biological activity and highly dependent on the copolymer composition.     

Modelling of emulsion copolymer microstructure

A model has been developed to describe stages II and III of batch emulsion copolymerization, and its predictive capabilities have been investigated by application to the system styrene-methyl acrylate. The main reaction site is considered to be the monomer-swollen polymer particle. Copolymerization rate and copolymer microstructure (molar-mass-chemical-composition distribution and sequence distribution at the triad level) are controlled by the local concentrations of monomers and free radicals inside the particles. The model accounts for radical absorption and desorption processes, bimolecular termination within the particles, and transfer to monomer and chain transfer agent. Monomer partitioning is described using experimentally determined relations. The results include rate of (co)polymerization. composition drift and copolymer microstructure. It is demonstrated that ‘apparent’ reactivity ratios are generally incapable of describing the course of emulsion copolymerizations in an adequate manner.     

Graft Copolymerization of Acrylamide onto Oil Palm Empty Fruit Bunch (OPEFB) Fiber

Grafting of acrylamide (AAm) onto oil palm empty fruits bunch fiber using hydrogen peroxide as initiator and methyl acrylate as comonomer was investigated. The amount of comonomer needed to make grafting of acrylamide possible was determined. The percentage of poly(acrylamide) and the comonomer in the final graft copolymer was estimated by elemental analysis. Results obtained indicated that methyl acrylate facilitated the incorporation of acrylamide monomer onto OPEFB. The reactivity ratios for both monomers were determined by using Fineman–Ross plot. The effects of reaction temperature and period as well as amount of the initiator, solvent, monomer and comonomer on the percentage of grafting at fixed amount of comonomer (11 mmol) were studied. Maximum percentage of grafting was achieved when the amount of initiator and solvent 3.98×10⁻³ mol and 50 mL respectively. The optimum reaction temperature was 50 ^○C and the reaction period was 90 min. Highest percentage of grafting was 232% when 25.6 mmol of acrylamide was used under these optimum conditions. The presence of functional group in the grafted polymer is characterized by infrared spectroscopy and the surface morphology is observed by scanning electron microscopy. Thermoanalytic investigation on OPEFB and OPEFB-g-PAAM were carried out to evaluate the thermal stability and respective activation energy of the materials.     

Graft copolymerization of methyl acrylate onto poly(vinyl alcohol) initiated by potassium diperiodatoargentate(III)

The graft copolymerization of methyl acrylate onto poly(vinyl alcohol) (PVA) using potassium diperiodatoargentate(III) [Ag(III)]–PVA redox system as initiator was studied in an alkaline medium. Some structural features and properties of the graft copolymer were confirmed by Fourier‐transfer infrared spectroscopy, scanning electron microscope, X‐ray diffraction and thermogravimetric analysis. The grafting parameters were determined as a function of concentrations of monomer, initiator, macromolecular backbone (X?_n = 1750, M? = 80 000 g mol^?1), reaction temperature and reaction time. A mechanism based on two single‐electron transfer steps is proposed to explain the formation of radicals and the initiation profile. Other acrylate monomers, such as methyl methacrylate, ethyl acrylate and n‐butyl acrylate, were also used to produce graft copolymerizations. It has been confirmed that grafting occurred to some degree. Thermogravimetric analysis was performed in a study of the moisture resistance of the graft copolymer. Copyright © 2004 Society of Chemical Industry     

The preparation of some block copolymers

The reactivity of the double bonds in p-divinylbenzene toward anionic reagents is much greater than is the residual double bond in the divinylbenzene unit incorporated in a polymer chain. Thus it is possible to add to a “living” polymer a few divinylbenzene units before appreciable crosslinking occurs. Each of these units will have a vinyl group conjugated with a phenyl ring and will be comparable in reactivity to styrene. If the reaction is stopped at this point by the addition of methanol, the molecular weight of the product is essentially that of the original living polymer. These polymers may then be copolymerized through these active double bonds with any monomer with which styrene may be copolymerized, to form block or graft-like copolymers. The copolymerizations may be effected by any of the methods applicable to styrene, i.e., free radical, cationic, or anionic. Such copolymerizations have been attempted with methyl methacrylate, butyl acrylate, vinyl chloride, vinylidene chloride, vinyl acetate, butadiene, isobutene, and propene, usually successfully.     

Copolymerizations of esters and glycerides of unsaturated C18 fatty acids with ethyl acrylate and acrylonitrile

This work was undertaken to assay the possibilities of making useful copolymers from linseed and similar oils. Methyl esters of linoleic, conjugated linoleic, linolenic, and alkali-cyclized linolenic acid have been copolymerized with ethyl acrylate at 60C and monomer reactivity ratios have been determined. In comparison with benzene or methyl stearate as inert diluents, all of these esters and several glycerides with conjugated or unconjugated unsaturation, and also 3,5,7-decatriene as a model compound, retard the polymerization of ethyl acrylate. Methyl eleostearate and the decatriene are unusually strong retarders of polymerizations of styrene, acrylonitrile, and ethyl acrylate, increasing retardation in the order given. Several experiments on copolymerizations of acrylonitrile with linseed oil at 60–130C show that the copolymerizations which incorporate much oil in the copolymer are slow but that the isolated copolymers have good drying and film-forming properties.     

Copolymerization of Methyl Methacrylate,Ethyl Acrylate,and Butyl Acrylate with N-2-Anisylmaleimide and Characterization of the Copolymers

The free radical copolymerizations of methyl methacrylate (MMA), ethyl acrylate (EA), and butyl acrylate (BA) with N-2-Anisylmaleimide (AMI), initiated by AIBN, were performed in THF solvent at 65°C. A series of copolymers of AMI-MMA, AMI-EA, and AMI-BA were prepared using different feed ratios of comonomers. The polymer samples have been characterized by solubility tests, intrinsic viscosity measurements, FT-IR, and ¹H-NMR spectral analysis, and thermo-gravimetric analysis. The values of monomer reactivity ratios r₁ and r₂ determined by Fineman-Ross and Kelen-Tudos methods are 0.43 and 0.42 in AMI/MMA, 0.72 and 0.62 in AMI/EA and 0.76 and 0.72 in AMI/BA systems. Alfrey-Price Q-e values for AMI are Q = 3.13 and e = 1.71 in AMI/MMA, Q = 1.10 and e = 1.46 in AMI/EA and Q = 1.02 and e = 1.63 in AMI/BA systems. It was found that the initial and final decomposition temperature increased with increasing the component of AMI in the copolymer.     

Controlled/living free-radical copolymerization of allyl glycidyl ether with methyl acrylate under Co γ-ray irradiation

An investigation on the copolymerization of allyl glycidyl ether (AGE), an epoxy-functional monomer, with methyl acrylate (MA) was performed in the presence of benzyl 1H-imidazole-1-carbodithioate (BICDT) under ⁶⁰Co γ-ray irradiation. The polymerizations revealed good characteristics of RAFT process. The content of AGE incorporation into the copolymer increased with higher monomer conversion and higher molar fraction of the AGE in the monomer feed. However, the polymerization could slow down when the fraction of AGE increased in the monomer feed, which might be attributed to the low activity of AGE. Taking advantage of RAFT process, functional block copolymer poly(AGE/MA)-block-poly(styrene) was prepared in the presence of poly(styrene) macroRAFT agent, and the copolymer was characterized by ¹H NMR spectra and GPC.     

Monomer-to-water ratios as a tool in controlling emulsion copolymer composition: The methyl acrylate–indene system

A drifting copolymer composition as a function of conversion is an aspect typical of copolymerization. Reducing this so-called composition drift in batch copolymerizations will lead to a decrease in chemical heterogeneity of the copolymers formed. For monomer systems in which the more water-soluble monomer is also the more reactive one, theory predicts that composition drift in emulsion copolymerization can be reduced or even minimized by optimizing the monomer-to-water ratio. The monomer combination methyl acrylate–indene (MA–Ind) meets the requirements needed to minimize composition drift in batch emulsion copolymerization. Therefore, this monomer combination is chosen as a model monomer system in order to verify this theoretical prediction. Reactivity ratios needed for model predictions have been determined by low conversion bulk polymerization, resulting in r_MA = 0.92 ± 0.16 and r_Ind = 0.086 ± 0.025. Furthermore, emulsion copolymerization reactions at the same monomer mole fraction are performed at different monomer to water ratios. From the good agreement between experiments and theoretical predictions for MA–Ind, it was concluded that control and even minimization of composition drift in batch emulsion copolymerization for monomer systems in which the more water-soluble monomer is also the more reactive one is indeed possible by changing the initial monomer-to-water ratio of the reaction mixture provided that the reactivity ratios of both monomers are not too far from unity. © 1994 John Wiley & Sons, Inc.     

Bulk and emulsion copolymerizations of n-butyl acrylate and poly(methyl methacrylate) macromonomer

Bulk and emulsion copolymerizations of an ω-unsaturated poly(methyl methacrylate) (PMMA) macromonomer with n-butyl acrylate (n-BA) were investigated. The reactivity of PMMA macromonomer in bulk copolymerization with n-BA was found to be lower than that of methyl methacrylate monomer with n-BA. The incorporation of PMMA macromonomer into poly(butyl acrylate) (PBA) latex particles by miniemulsion copolymerization was proved by high performance liquid chromatography-silica adsorption spectroscopy. Dynamic mechanical studies showed that PMMA macromonomer was grafted to the PBA backbone, and the degree of grafting increased as the ratio of PMMA macromonomer to n-BA increased. Microphase separation of the PMMA macromonomer grafts was observed at higher ratio of macromonomer (higher or equal to 10% weight of macromonomer based on total polymer phase). The n-BA/PMMA macromonomer copolymer behaved completely differently from the physical blend of PBA and PMMA macromonomer particles of the same composition. © 1996 John Wiley & Sons, Inc.     

Effect of monomer composition on apparent chain transfer coefficient in reversible addition fragmentation transfer (RAFT) copolymerization

The effects of monomer composition on the apparent chain transfer coefficient (〈C_tr〉) in reversible addition fragmentation transfer (RAFT) copolymerization were investigated. The studied RAFT systems included methyl methacrylate (MMA)/butyl acrylate (BA) mediated by 1-phenylethyl phenyldithioacetate (PEPDTA) (i.e. MMA/BA-PEPDTA), MMA/BA by 2-cyanoprop-2-yl dithiobenzoate (i.e. MMA/BA-CPDTB), and styrene (St)/BA by benzyl dithioisobutyrate (i.e. St/BA-BDTiB). The R groups of the RAFT agents were first converted to the corresponding copolymer oligomers having the same composition to facilitate the measurement of the main RAFT equilibrium transfer coefficients. It was found that there exist minimum values in the 〈C_tr〉 ∼ f₁ curves in MMA/BA-CPDTB and St/BA-BDTiB at f₁ = 0.75 and 0.25, respectively. The apparent transfer coefficients of the copolymerization systems within some composition range were lower than their homopolymerization values. The lower 〈C_tr〉 values resulted in broader copolymer molecular weight distributions. The composition dependence of 〈C_tr〉 was determined by the comonomer reactivity ratios and the Z group functionality of the RAFT agent. The experimental data could be well described by a simple equation derived from the terminal model:

     

“Living”/controlled polymerization of methyl acrylate mediated by dithiocarbamates under γ‐ray irradiation

γ‐Ray initiated reversible addition–fragmentation chain transfer (RAFT) polymerizations of methyl acrylate (MA) were investigated in bulk using five different dithiocarbamate structures, 2‐phenyl‐benzoimidazole‐1‐carbodithioic acid benzyl ester ( 1b ), 2‐methyl‐benzoimidazole‐1‐carbodithioic acid benzyl ester ( 1c ), 2‐pheny‐indole‐1‐cardithioic acid benzyl ester ( 1d ), 2‐(carbazole‐9‐carbothioylsulfanyl)‐2‐methyl‐propionic acid ester ( 1e ), and carbazole‐9‐carbodithioic acid naphthalene‐1‐ylmethyl ester ( 1f ), as RAFT agents. The experiment results showed that MA polymerized in a controlled way under a low irradiation dose rate, i.e., first‐order kinetic plots, the experimental molecular weights increased linearly with monomer conversions. The polydispersity indices of polymers generally remained at a relatively low value (lower than 1.4). The effect of irradiation dose on the polymerization results was investigated. The obtained polymers were characterized with ¹H NMR and GPC. Chain‐extension reaction was also successfully carried out using the obtained polymer as the macro‐RAFT agent and styrene as the second monomer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1769–1775, 2007     

Organotin polymers. IX. Copolymerization parameters of di-(tri-n-butyltin) itaconate with styrene and methyl methacrylate

Copolymerization reactions of di-(tri-n-butyltin) itaconate with styrene and methyl methacrylate were carried out in solution at 70°C using 1 mol% azobisisobutyronitrile as a free radical initiator. The copolymer compositions were determined by chemical analysis as well as from ¹H-NMR data. The monomer reactivity ratios for copolymerizations of di-(tri-n-butyltin) itaconate with styrene and methyl methacrylate have been found to be r₁ = 0.228, r₂ = 0.677, and r₁ = 0.220, r₂ = 1.635, respectively. The sequence distribution of the triad fractions were calculated from reactivity ratios and compared with those obtained from ¹H-NMR data.     

Organotin polymers XIV. Synthesis and copolymerization reactions of p-acryloyloxy-tri-n-butyltin benzoate with some vinyl monomers

p-Acryloyloxy-tri-n-butyltin benzoate (ABTB) was prepared by the reaction of p-hydroxy-tri-n-butyltin benzoate and acrylic acid in the presence of dicyclohexylcarbodiimide. The monomer reactivity ratios for the copolymerizations of ABTB (M₁) with methyl acrylate (M₂), ethyl acrylate (M₂), n-butyl acrylate (M₂), methyl methacrylate (M₂), styrene (M₂) and acrylonitrile (M₂) have been found to be r₁ = 0.080, r₂ = 1.046; r₁ = 0.039, r₂ = 1.585; r₁ = 0.019, r₂ = 2.076; r₁ = 0.150, r₂ = 1.710; r₁ = 0.113, r₂ = 1.339 and r₁ = 0.007, r₂ = 2.853, respectively. The Q and e values for the prepared organotin monomer were calculated. Copolymerization reactions were carried out in solution at 70°C using 1 mol-% azobisisobutyronitrile. The structure of the ABTB monomer and the prepared copolymers was investigated by IR and ¹H-NMR spectroscopy.