Bulk Polymerization Of Methyl Methacrylate Research Articles

?Living? radical polymerization of methyl methacrylate with diethyl 2,3-dicyano-2,3-diphenylsuccinate as a thermal iniferter

The bulk polymerization of methyl methacrylate (MMA) initiated with diethyl 2,3-dicyano-2,3-diphenylsuccinate (DCDPS) was studied. This polymerization showed some “living” characteristics; that is, both the yield and the molecular weight of the resulting polymers increased with reaction time, and the resultant polymer can be extended by adding MMA. The molecular weight distribution of PMMA obtained at high conversion is fairly narrow (Mw/Mn = 1.24≈1.34). It was confirmed that DCDPS can serve as a thermal iniferter for MMA polymerization by a “living” radical mechanism. Furthermore, the PMMA obtained can act as a macroinitiator for radical polymerization of styrene (St) to give a block copolymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4610–4615, 1999

10-I-3 Iodanes * as photoiniferters with spectral selectivity

A photoiniferter ability of the 10-I-3 iodanes* is established during the bulk polymerization of methyl methacrylate, styrene and N-vinylpyrrolidone. The observed spectral selectivity is its important peculiarity, opening new possibilities for the control of the macromolecule microstructure. Under visible light these iodanes initiate the “pseudoliving” radical polymerization, while a conventional radical or cationic polymerization are the consequences of the iodane decomposition under UV irradiation. It is suggested that the spectral selectivity of the 9-I-2 iodanyl radical decomposition and the relative instability of the ends of the iodane macromolecule are the reasons of this unusual iodane ability.

Algorithms for Using Some Models of Gel and Glass Effects in Free-Radical Polymerization of Methyl Methacrylate

The aim of this article is the modeling and simulation of the batch bulk polymerization of methyl methacrylate (MMA). Simple dependencies between the propagation and termination rate constants and monomer conversion for the gel and glass effects are proposed. The empirical parameters in these relations are determined from conversion and molecular-weight experimental data obtained under various reaction conditions (initiator concentration and temperature). Sometimes, different relations were necessary to express the variation of the kinetic constants on conversion subintervals. Thus, these models have been used continuously or discontinuously, as a function of their results. An algorithm for using this model was also established. The analysis of this model has two aims: (1) to get a good agreement between simulation and experiment; (2) to provide a simple model to be used under different reactor conditions (batch, semibatch, or continuous) or which can be easily handled in polymer engineering studies, such as sensitivity analysis, optimal control, and so forth.

Software sensor for the bulk polymerization of systems exhibiting the trommsdorff effect using viscosity measurements

A model-predictive software sensor was developed for on-line estimation of monomer conversion and average molecular weight during bulk polymerization of systems exhibiting a gel effect. The viscosity and temperature of the reaction mass are the measured secondary variables, which when used with the model allow the state of the system to be estimated. The viscometer-reactor assembly was modified so as to measure the viscosity of the reaction mass during bulk polymerization of methyl methacrylate (MMA) at temperatures higher than those reported in our earlier work (Mankar, R. B.; Saraf, D. N.; Gupta, S. K. Ind Eng Chem Res 1998, 37, 2436).The viscosity data were curve-fitted using the modified Martin equation. Optimal temperature histories were then computed off-line, using a genetic algorithm, and implemented on the viscometer-reactor assembly in which the bulk MMA polymerization was carried out. The fact that the model tuned with the data obtained under the isothermal reactor operation can be used to predict the viscosity for nonisothermal (optimal or otherwise) reactor conditions without further tuning establishes the efficacy of the software sensor. This study can now be extended to investigate, experimentally, the on-line optimizing control of bulk MMA polymerizations. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2309–2326, 1999

Addition-fragmentation behavior of a capto-dative group-substituted acrylic ester in free-radical polymerization and reactivity of the derived macromonomers

Ethyl-2-(2-cyano-2-ethylthio)-ethyl-propenoate (ECEP) was synthesized and examined as free-radical addition–fragmentation chain transfer agent (AFCTA) in the bulk polymerization of methyl methacrylate (MMA) and styrene at various temperatures. A better chain transfer constant (Ctr) was observed for styrene than for MMA, projecting the potentiality of the compound as a better end-functionalizing agent for the former. In both cases, copolymerization of ECEP with the monomer predominated over fragmentation, the relative proportions of which were dependent on the monomer. The ECEP-terminated radical fragmented to an extent of 26% in the presence of MMA, whereas it was only 9.5% in the case of styrene. The relative extent of fragmentation and copolymerization was in conformation to the calculated reactivity ratios and chain transfer constants. Addition–fragmentation chain transfer resulted in the formation of methacrylic-functional macromonomers. The copolymerizability of the resultant macromonomer was found to depend on the nature of the backbone and on the comonomer. On copolymerizing with MMA, the terminal monomer moiety on polystyrene (PS)-based macromonomers preferred to undergo fragmentation, whereas that of the polymethyl methacrylate (PMMA)-based one copolymerized readily with styrene because of thermodynamic and kinetic factors. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2511–2524, 1999

Instationary polymerization technique—basic principles and first results

Abstract Basic principles of a new polymerization technique and the subsequent analysis of the resultant molar mass distribution for the direct determination of the rate constant for chain propagation are introduced. First results are presented for the bulk polymerization of methyl methacrylate at room temperature. It is demonstrated, that the correlation between the active life time of a radical chain and the number of propagation steps, L act = k p [M] t act is valid in the case of instationary polymerization conditions too.

Effect of Radical Initiators on the Size and Formation of Silver Nanoclusters in Poly(methyl methacrylate)

Silver nanoclusters in poly(methyl methacrylate) (Ag/PMMA) were prepared by bulk polymerization of methyl methacrylate with radical initiators in the presence of silver(I) trifluoroacetate (AgTfa), followed by a period of heating. To compare the influence of the type of radical initiator on the formation of Ag nanoclusters, 2,2‘-azobisisobutyronitrile (AIBN) and benzoyl peroxide (BPO) were chosen as initiators. On the basis of the characterization of the solid sols of Ag/PMMA thus prepared, it was revealed by visible spectroscopy and TEM that the size of Ag nanoparticles increases with increasing initial concentration of AIBN and decreases with increasing initial concentration of BPO.

Chain-length dependent termination in pulsed-laser polymerization, 6. The evaluation of the rate coefficient of bimolecular terminationkt for the reference system methyl methacrylate in bulk at 25°C

The values for the rate coefficient of chain termination kt in the bulk polymerization of methyl methacrylate at 25°C were formally calculated (i) from the second moment of the chain-length distribution and (ii) from the rate equation for laser-initiated pseudostationary polymerization (both expressions were originally derived for chain-length independent termination) by inserting the appropriate experimental data including the rate constant of chain propagation kp. These values were treated as average values, k and k, respectively. They exhibited good mutual agreement, even the predicted gradation (k < k by about 20%) was recovered. The log-log plot of kt vs. the average degree of polymerization of the chains at the moment of their termination v′ yielded exponents b of 0.16–0.17 in the power-law kt = A · v′−b, A ranging from 1.1 × 108 to 1.3 × 108 (L · mol−1 · s−1). A 70% contribution of disproportionation to overall termination has been assumed in the calculations.

Thermal Polymerization of Methyl Methacrylate at High Temperature

Abstract Kinetic studies of the bulk polymerization of methyl methacrylate at high temperature have been carried out first without any additives and then in the presence of 1-Butanethiol as a chain transfer agent. A pressurised dilatometric reactor operating at high temperature is used to determine the time-conversion curves at temperatures between 150 and 180°C. A two-stage polymerization is observed. The high polymerization rate obtained initially is attributed to traces of an initiating impurity, while the second, slower polymerization stage could be considered as the actual thermal polymerization. The chain transfer agent or an impurity it may contain also initiates the reaction. Therefore, the rates of both the initial polymerization and of the second stage are increased when the thiol is added. Experimental data on the degree of conversion versus time and on the final average molecular weight are used to determine the chain transfer constants to the monomer and to the mercaptan as well as the initiation rate constants. These constants are used to model the thermal polymerization of MMA at high temperatures where these initiation reactions can no longer be neglected, especially when an industrial polymerization process has to be optimized and controlled.

Termination Kinetics of Methyl Methacrylate Free-Radical Polymerization Studied by Time-Resolved Pulsed Laser Experiments

The SP−PLP technique has been applied to measure kt/kp, the ratio of termination to propagation rate coefficients, for the free-radical bulk polymerization of methyl methacrylate at 1000 bar and several temperatures ranging from 40 to 100 °C. kt/kp is obtained from time resolved (μs) near-infrared measurement of monomer conversion induced by a single laser pulse of about 20 ns width. A total of 80 such single pulse (SP) signals were co-added to yield a concentration vs time trace of sufficient signal-to-noise quality to deduce kt/kp with an accuracy of better than ±40%. With kp being known from the well-established PLP−SEC procedure, kt/kp data directly yield individual (chain-length averaged) termination rate coefficients, referring to a fairly narrow range of monomer conversion. The SP−PLP technique, which seemed to be restricted to investigations into high kp monomers such as ethene (at high temperatures) and the acrylates, within the present work on MMA is demonstrated to be suitable for kinetic studi...

On-Line Optimizing Control of Bulk Polymerizations: 1. Development of a Software Sensor

A viscometer-reactor assembly has been developed and bulk polymerization of methyl methacrylate carried out in it. The viscosity of the polymerizing mixture has been measured continuously at two different temperatures (isothermal) and initiator loadings. Samples of the reaction mass have also been taken out at several different times and analyzed for monomer conversion and the weight-average molecular weight. The data obtained have been curve-fitted using the Martin equation with KM treated as an empirical parameter. The use of experimental data on the viscosity of the reaction mass during polymerization as a state estimator (software sensor) has been demonstrated. The viscometer-reactor assembly can be used to obtain viscosity under nonisothermal conditions as well, and also to study on-line optimizing control of bulk polymerizations using appropriate on-line model-based state variable estimation and optimization software codes.

Maleimido-fluoroprobe: A Dual-Purpose Fluorogenic Probe of Polymerization Dynamics

Maleimido-fluoroprobe (MFP) is a derivative of “fluoroprobe” (FP), the most sensitive known fluorescent polarity probe. MFP differs from FP in that it is completely nonfluorescent. The characteristic strong FP-type fluorescence is however switched on when the CC bond of the maleimide group becomes saturated forming the succinimide derivative, SFP. This fluorogenic behavior is shown to be induced by copolymerization of MFP into growing polyacrylate chains. The increase in the intensity of the fluorescence, which is observable even in the early, low-viscosity stage of polymerization, provides therefore a measure of the degree of polymerization. The strong blue shift of the fluorescence of chain-incorporated SFP moieties fulfills the usual polarity probe function of monitoring changes in the microscopic dielectric environment of the polymer as vitrification takes place. This duality in the probe characteristics of MFP is illustrated by results on the radiation-induced bulk polymerization of methyl methacrylate.

Molecular Weight Distributions in Free-Radical Polymerizations. 2. Low-Conversion Bulk Polymerization

Results are reported for the low-conversion bulk polymerizations of methyl methacrylate (up to 15% conversion) and styrene (up to 8%) at 50°C with AIBN as the initiator. The rates were measured gravimetrically, and the time evolution of the full molecular weight distributions (MWDs) were measured by GPC. For both monomers, the rates obeyed [AIBN]0.5±0.05 ,independent of conversion. MWD data were analyzed as In P(M), where P(M) is the pseudoinstantaneous number distribution; approximate analytic solutions for the MWD suggest that plots of InP(M) vs M should show extensive linear regions if chain stoppage is by transfer, disproportionation, and or chain-length-dependent termination. The cumulative number distribution is approximately the GPC distribution divided by the square of the molecular weight; pseudoinstantaneous number distributions were obtained by subtracting the appropriately normalized cumulative distributions at successive conversions. All MWD data show In P(M) is linear in M for higher M, with the slope of this region being independent of conversion but increasing significantly with increasing (AIBN). The combined MWD and rate data for styrene are consistent with chain stoppage being both by transfer to monomer and by termination (by combination) between long and short chains, long-long termination being too slow to be important; parameter values reproducing both the rate and the MWD involve both chain-length-dependent and chain-length-independent events, with the critical distance of interaction for termination being significantly greater than that of a monomer unit (as distinct from what is seen at intermediate conversion). For MMA, where termination is dominated by disproportionation, the rate and MWD data are best fitted by assuming that center-of-mass (chain-length-dependent) termination is at most only weakly rate-determining. Attempts to use the low-M shape of plots of In P(M) to indicate whether termination occurs by combination or disproportionation were inconclusive.

Differential scanning calorimetry as a method for kinetic studies of polymerization. Part I. Bulk polymerization of methyl methacrylate

Differential scanning calorimetry as a method for kinetic studies of polymerization. Part I. Bulk polymerization of methyl methacrylate

Modeling of free radical polymerization up to high conversion. II. Development of a mathematical model

In free radical polymerization diffusion-controlled processes take place simultaneously to the normal chemical reactions. Despite extensive efforts to model such processes a consistent model for the design of a polymerization reactor has not yet been established. In this article a semiempirical model describing the conversion, polymerization degree, and molecular weight distribution (MWD) for the free radical polymerization is developed for the entire course of the reaction. The model includes the change of termination, propagation, transfer, and initiation rate. By simultaneous parameter estimation from the conversion and degrees of polymerization data the model parameters have been determined for isothermal polymerizations of methyl methacrylate (MMA) and styrene (ST). The simulation results for the conversion, degrees of polymerization, and MWD are in good accordance with experimental data for suspension and bulk polymerization of MMA and ST up to very high conversions. The influence of diffusion on the propagation rate in case of polymerization of MMA is negligible compared to the influence of the cage effect on the radical efficiency; in case of ST polymerization both effects must be included in the kinetic model. The model presented is also tested for polymerizations conducted in the presence of solvent and/or chain transfer agents.

Amine activators for the ?cool? peroxide initiated polymerization of acrylic monomers

Two tertiary amines with a chemical structure rather similar to dimethyl-4-toluidine have been prepared and tested as activators for the free radical polymerization of methyl methacrylate. 4-Dimethylaminobenzyl alcohol, DMOH, was synthesized by reduction of the corresponding benzaldehyde. 4-Dimethylaminobenzyl methacrylate, DMMO, was synthesized by condensation of methacryloyl chloride with DMOH in the presence of triethylamine as catalyst. Kinetic studies of the bulk polymerization of methyl methacrylate initiated by the redox system BPO–amine have been carried out by differential scanning calorimetry at different temperatures in the interval 30–40°C. An increase of the overall rate constant, k, with increasing temperature was observed for all redox systems. The system BPO/DMT gave the highest values of k. The polymerizations catalyzed by DMOH and DMMO respectively gave lower values of the overall Arrhenius activation than that obtained with DMT. DMMO may participate in the polymerization not only as activator but also as an acrylic derivative which can be incorporated into the polymeric growing chains during the propagation step of the free radical polymerization. © 1996 John Wiley & Sons, Inc.

Effect of a π‐donor on the radical bulk polymerization of methyl methacrylate

AbstractBulk polymerizations of methyl methacrylate (MMA) at 60°C initiated with 2,2′‐azoisobutyronitrile are influenced by the presence of an organic π‐donor such as tetrathiafulvalene (TTF). Upon addition of TTF, the ratio of weight‐ to number‐average molecular weights M̄w/M̄n are significantly reduced and the thermal stability of the poly(methyl methacrylate) samples is increased. Kinetic investigations indicate that TTF acts as a retarder on the polymerization mechanism.

Free radical polymerizations associated with the trommsdorff effect under semibatch reactor conditions. II: Experimental responses to step changes in temperature

AbstractSeveral free radical addition polymerizations exhibit the diffusion limited gel or Trommsdorff effect. The models available until recently could not be applied to industrially important semibatch operations and to nonisothermal polymerizations. The recent model of Ray et al. (24) can indeed be applied to such situations. In this study, an experimental setup to study polymerizations under such conditions has been assembled. Methyl methacrylate (MMA) is polymerized in a 1‐liter stainless steel, computer‐controlled reactor. A series of experiments on bulk polymerization of MMA under different temperature histories (near‐isothermal, step decrease, and step increase) at a fixed initiator (AIBN) concentration of 25.8 mol/m3 have been conducted. Two important process output variables, namely, monomer conversion and average molecular weight, have been measured off‐line at different sampling times during the course of polymerization. The conversion and molecular weight data are found to be in reasonable accord with model (24) predictions obtained using the experimental (nonisothermal) temperature histories, and best fit correlations for three parameters evaluated using earlier data from the literature on isothermal batch reactors (with no further curve fitting). The new model (24) can, thus, be used with some degree of confidence to design and control larger scale reactors.

Vapour Liquid Equilibrium of Methyl Methacrylate and Polymethyl Methacrulate for Estimation of Devolatilization Ability of Vent Extruder.

The χ-parameter in the Flory-Huggins equation of methyl methacrylate and polymethyl methacrylate was determined to be χ=0.33, from the observation of vapour pressure of the reaction mixture in a pilot scale reactor for continuous bulk polymerization of methyl methacrylate. The monomer content of the polymer solution flushed from the pressurized heat exchanger to the vent extruder almost agreed with the equilibrium concentration calculated from the Flory-Huggins equation. The monomer content of the resulting pellet (0.150.37%) was far from the equilibrium concentration (0.02%) at the front vent, suggesting that the monomer content must be decreased by improvement of the screw design.

Effect of photoinitiator on the molar mass distribution obtained from a pulsed laser polymerization

AbstractThe choice of the photoinitiator is not usually regarded as being as important consideration in attempting to determine the value of the propagation rate coefficient kp from a pulsed laser‐initiated polymerization (PLP). It is shown that in fact the choice of the photoinitiator can profoundly influence the success of such experiments. Specially, for a number of monomers it was found that the successful determination of kp is essentially impossible when 1,1‐azodicyclohexanecarbonitrile is employed as a photoinitiator. The likely reason for this phenomenon is discussed from which it would seem appropriate to be wary in using any azo compound as a PLP photoinitiator. From PLP experiments with a non‐azo photoinitiator, ambient pressure kp has been determined for bulk polymerization of methyl methacrylate over an extended temperature range.