Conversion Of Methyl Methacrylate Research Articles

Addition–fragmentation chain transfer: Molecular weight distributions and retardation in the system methyl methacrylate/methyl α‐(bromomethyl)acrylate

AbstractA detailed investigation of addition–fragmentation chain transfer (AFCT) in the free‐radical polymerization of methyl methacrylate (MMA) in the presence of methyl α‐(bromomethyl)acrylate (MBMA) was carried out to elucidate mechanistic details with efficient macromonomer synthesis as an underlying goal. Advanced modeling techniques were used in connection with the experimental work. Curve fitting of simulated and experimental molecular weight distributions with respect to the rate coefficient for addition of propagating radicals to MBMA (kadd) over 60–120 °C resulted in Eadd = 21.7 kJ mol−1 and Aadd = 2.18 × 106 M−1 s−1 and a very weak temperature dependence of the chain‐transfer constant (Eadd ≈ Ep). The rate coefficient for fragmentation of adduct radicals at 60 °C was estimated as kf ≈ 39 s−1 on the basis of experimental data of the MMA conversion and the concentration of 2‐carbomethoxy‐2‐propenyl end groups. The approach developed is generic and can be applied to any AFCT system in which copolymerization does not occur and in which the resulting unsaturated end groups do not undergo further reactions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2640–2650, 2004

Ansa-Zirconocene ester enolates: synthesis, structure, reaction with organo-lewis acids, and application to polymerization of methacrylates.

The synthesis, structural characterization, and abstraction chemistry of ansa-zirconocene ester enolate complexes relevant to the isospecific polymerization of methacrylates are reported. Reactions of rac-(EBI)ZrMe(OTf) and rac-(EBI)Zr(OTf)(2) [EBI = C(2)H(4)(Ind)(2)] with 1 and 2 equiv of lithium isopropylisobutyrate in toluene produce the first examples of ansa-zirconocene mono- and diester enolate complexes: rac-(EBI)ZrMe[OC(O(i)Pr)=CMe(2)] (1) and rac-(EBI)Zr[OC(O(i)Pr)=CMe(2)](2) (2) in 89% and 50% isolated yields, respectively. The reaction of 1 with B(C(6)F(5))(3) was investigated in six different organic solvents; in THF at ambient temperature, this reaction cleanly produces the isolable cationic ansa-zirconocene ester enolate complex rac-(EBI)Zr(+)(THF)[OC(O(i)Pr)=CMe(2)][MeB(C(6)F(5))(3)](-) (3) in quantitative yield. The analogous reaction of 1 with Al(C(6)F(5))(3) in toluene, however, proceeds through a proposed novel, intramolecular proton transfer process in which propylene is eliminated from the isopropoxy group, subsequently producing a carboxylate-bridged tight ion pair rac-(EBI)Zr(+)(Me)OC((i)Pr)OAl(C(6)F(5))(3)(-) (4). In addition to standard spectroscopic and analytical characterizations for the isolated complexes 1-4, complexes 2 and 4 have also been structurally characterized by X-ray diffraction studies. Polymerization of methyl methacrylate (MMA) and n-butyl methacrylate (BMA) has been investigated using complexes 1, 3, and 4. Both the isolated cationic 3 and neutral 1 (the latter combined with B(C(6)F(5))(3) in situ) are highly active (10 min for quantitative MMA conversion) and highly isospecific ([mm] > 95% for PMMA; [mm] > 99% for PBMA) via enantiomorphic-site control, producing polymethacrylates with extremely narrow molecular weight distributions (M(w)/M(n) = 1.03). The aluminate complex 4, however, produces syndiotactic PMMA predominantly via chain-end control.

Preparation of high molecular weight poly(methyl methacrylate) with high yield by room temperature suspension polymerization of methyl methacrylate

To obtain high molecular weight (HMW) poly(methyl methacrylate) (PMMA) with high conversion, methyl methacrylate (MMA) was polymerized in suspension using a room temperature initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN), and the effects of polymerization conditions on the polymerization behavior of MMA and the molecular parameters of PMMA were investigated. On the whole, the experimental results well corresponded to the theoretically predicted tendencies. These effects could be explained by a kinetic order of ADMVN concentration calculated by an initial rate method and an activation energy difference of polymerization obtained from the Arrhenius plot. Suspension polymerization at 25 °C by adopting ADMVN proved to be successful in obtaining PMMA of HMW (number-average degree of polymerization (Pn): 30,900–36,100) and of high yield (ultimate conversion of MMA into PMMA: 83–93 %) with diminishing heat generated during polymerization. The Pn and lightness were higher and polydispersity index was lower with PMMA polymerized at lower temperatures.

Synthesis of Poly(IB‐co‐VBDC)‐g‐PMMA via Photo‐initiated Free Radical Graft Polymerization

Photoinitiated free radical graft polymerization of methyl methacrylate (MMA) with poly[isobutene‐co‐(4‐vinyl benzyl N,N‐diethyldithiocarbamate)] [poly(IB‐co‐VBDC)] as macromolecular iniferter was investigated. The polymerization proceeds to give a high yield graft copolymer, however it was observed that even in the early stage of the polymerization there formed an insoluble polymer. In the presence of tetraethylthiuram disulfide (TETD) the gel fraction of the yield graft copolymer was drastically reduced and the polymerization was retarded as well. When the [TETD]/[VBDC] increased from 0 to 1.0, the gel fraction of the graft copolymer decreased from 33.2% to 1.6% (wt) while the fraction of the homopolymer of the MMA increased from 4.5% to 10.5% (wt). With the increasing of the UV irradiation time, both the MMA conversion and the molecular weight of the graft copolymer increased readily.

Stereoblock Copolymerization of Propylene and Methyl Methacrylate with Single‐Site Metallocene Catalysts

AbstractSequential stereoblock copolymerization of propylene (P) and methyl methacrylate (MMA) using Group IV single‐site metallocene catalysts efficiently produces PP‐b‐PMMA stereodiblock copolymers. When activated with B(C6F5)3, C2‐symmetric rac‐Et(Ind)2ZrMe2 yields isotactic‐PP‐b‐isotactic‐PMMA diblock copolymer, whereas Cs‐symmetric Me2Si(C5Me4)(tBuN)TiMe2 affords atactic‐PP‐b‐syndiotactic‐PMMA diblock copolymer. In the copolymerization catalyzed by the C2‐symmetric catalyst, a very small amount of PMMA homopolymer formed can be removed from the copolymer by extracting the bulk polymer product with boiling methylene chloride. However, separation of isotactic PP formed if any from the copolymer product approves very difficult, due to very similar solubility between the diblock copolymer and isotactic PP homopolymer in various high‐boiling chlorinated solvents. On the other hand, in the copolymerization catalyzed by the Cs‐symmetric catalyst, both PMMA and atactic PP homopolymers formed in small weight fractions during the copolymerization can be successfully removed from the predominant copolymer product by solvent extraction using boiling heptane. After successful removal of both homopolymers, for example, an atactic‐PP‐b‐syndiotactic‐PMMA diblock copolymer has high molecular weight (Mn = 21 100), narrow molecular weight distribution (PDI = 1.08), high PMMA incorporation (33.8 mol‐% of PMMA), and moderate syndiotacticity for the PMMA block ([rr] ≈ 80%). Furthermore, the comonomer composition in the copolymer can be controlled by the time for propylene polymerization and the conversion of MMA. A pronounced activator effect is observed; when the same Cs‐symmetric catalyst is activated with Ph3CB(C6F5)4, formation of homopolymers is predominated. magnified image

Continuous atom transfer radical block copolymerization of methacrylates

AbstractA column reactor packed with silica‐gel‐supported copper bromide (CuBr)–hexamethyltriethylenetetramine (HMTETA) was developed for the continuous‐transition–metal‐mediated living/controlled radical polymerization [atom transfer radical polymerization (ATRP)] for homo‐ and block copolymerization of methyl methacrylate (MMA). The reactor showed good stability (>100 h) in both catalyst activity and molecular weight of the poly(methyl methacrylate) (PMMA) produced. The MMA conversion decreased as the flow rate increased. The polymerization in the reactor was in first order with respect to monomer concentration. The molecular weight of the resulting PMMA increased linearly with MMA conversion, exhibiting the characteristic feature of living polymerization. Thus, simply changing the flow rate of MMA, which in turn determined the MMA conversion, readily controlled the molecular weight of PMMA. The block copolymerization of MMA with n‐butyl methacrylate (nBMA) was carried out using two reactors connected in series. The block copolymers were slightly contaminated by PMMA prepolymer from the first column. The molecular weight of the nBMA block could be changed by the flow rate of the nBMA in the second reactor. This packed column reactor technology is feasible for continuously synthesizing polymers or block copolymers with controlled molecular weights that are readily adjustable by changing the monomer flow rates.

On-line conversion monitoring of the solution polymerization of methyl methacrylate using near-infrared spectroscopy

Fiber-optic near-infrared (NIR) spectroscopy was successfully used to monitor the conversion of monomer during the solution polymerization of methyl methacrylate (MMA) carried out in a lab-scale reactor. NIR spectra were recorded during 18 batch and semi-continuous reactions using an in-situ transmission probe. An empirical model was generated using partial least-squares regression (PLS) to relate the NIR spectral data to the conversion measured off line by gravimetry. The obtained calibration was characterized by a correlation coefficient of 99.45% and a standard error of calibration (SEC) equal to 1.95%. The measurements were then validated for various operating conditions and for both batch and semi-continuous modes. The conversion was measured with a standard error below 2.6%, in the worst case scenario. The on-line NIR measurement of conversion was demonstrated to be accurate, robust, and suitable for versatile use in the polymerization plant. Validation of the on-line measurement of MMA conversion during the semi-continuous Runs V2 and V3.

Neodymium(III)tert-Butoxide-Dialkylmagnesium, a New Initiator System for Syndiotactic Polymerization of Methyl Methacrylate

The polymerization of methyl methacrylate (MMA) in toluene at 0°C using combinations of dihexylmagnesium (Hex2Mg) with various metal tert-butoxides as initiators has been studied. Purely anionic initiator systems based on alkali metal salts allow complete conversion of MMA within 1 h to yield either highly isotactic PMMA (LiOt-Bu/MgR2 = 5, M̄n = 61 000, M̄w/M̄n = 1.95, 84% mm) or narrow polydispersity atactic PMMA (NaOt-Bu/MgR2 = 20, M̄n = 39 000 and M̄w/M̄n = 1.18). The combination of Hex2Mg with Nd3(Ot-Bu)9(THF)2 (Nd/Mg = 5–10) affords a novel initiator system that gives in 40–63% yield syndiotactic-rich PMMA (M̄n = 50–90 000, M̄w/M̄n = 1.06–1.12, 76–79% rr) with low initiation efficiency. In this case, characteristics of the polymers and polymerization reactivity data are consistent with the in situ generation of an alkylneodymium species.

Ultrasonically initiated emulsion polymerization of methyl methacrylate

AbstractThe ultrasonically initiated emulsion polymerization of methyl methacrylate (MMA) was investigated. Experimental results show that sodium dodecyl sulfonate (SDS) surfactant plays a very important role in obtaining a high polymer yield, because in the absence of SDS, monomer conversion is near zero. Thus, the surfactant serves as an initiator and as interfacial modifier in this system (MMA/H2O), and the monomer conversion increases significantly with increasing SDS concentration. An increase in the reactor temperature also leads to an increase in the monomer conversion. An appropriate increase in the N2 purging rate also leads to higher conversion. The conversion of MMA decreases with increasing monomer concentration because of the higher viscosity of the system. With the experimental results, optimized reaction conditions were obtained. Accordingly, a high monomer conversion of about 67% and a high molecular weight of several millions can be obtained in a period of about 30 min. Furthermore, transmission electron micrographs show that the latex particles prepared are nanosized, indicating a promising technique for preparing nanoscale latex particles with a small amount of surfactant. In conclusion, a promising technique for ultrasonically initiated emulsion polymerization has been successfully performed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3356–3364, 2001

A new polymerizable photoiniferter for preparing poly(methyl methacrylate) macromonomer

A new polymerizable photoiniferter containing the vinyl group, β-methacrylyoxylethyl 2- N, N-diethyldithiocarbamylacetate (MAEDCA), was prepared and used for initiating methyl methacrylate (MMA) polymerization in bulk and in benzene under UV light. The resultant Poly(MMA)-macromonomer bearing α-methacrylyoxylethyloxycarbonylmethyl and ω- N, N-diethyldithiocarbamyl end groups was produced. The molecular weight of the macromonomer depended on the conversion of MMA and concentration of MAEDCA. Characteristic results show that the bulk polymerization of MMA with MAEDCA proceeded as a “living” process at low monomer conversion. The “living” polymerization mechanism is proposed on the basis of radical trapping and electron paramagnetic resonance studies. The formation of graft copolymer PSt- graft-PMMA by copolymerization of PMMA-macromonomer with styrene is also performed.

Polymerization of methyl methacrylate by single component catalyst of lanthanocene chloride O(C 2H 4C 5H 3CH 3) 2LnCl (Ln=Y, Nd, Sm)

A novel single component catalyst of lanthanocene chloride O(C 2H 4C 5H 3CH 3) 2LnCl (Ln=Y, Nd, Sm) was used to initiate the polymerization of methyl methacrylate (MMA) in bulk and in toluene solution system. The effects of temperature, time and molar ratio of MMA/Catalyst were studied in detail. The results showed that higher temperature and longer time were favorable for increasing the catalytic activities. Both polymerization conversion of MMA and molecular weight (MW) of PMMA formed in toluene are lower than those from bulk polymerization, which gives M w as high as 1.52×10 6, and MMA conversion more than 80%. The syndiotacticity of PMMA prepared at a temperature ranging from 20°C to 80°C is about 65%. GPC (gel permeation chromatography) shows that the MW distribution of PMMA obtained in bulk polymerization is as narrow as 1.3. Kinetic studies indicate that the polymerization rate is a first-order dependence on the concentration of MMA and catalyst, respectively. The overall activation energy of polymerization is 33.9 kJ/mol.

The effects of process variables in the hydroformylation of methyl methacrylate with the in situ formed ( o-thiomethylphenyl)diphenylphosphine rhodium complex

The hydroformylation of methyl methacrylate (MMA) was studied with the in situ formed ( o-thiomethylphenyl)diphenylphosphine (SP) rhodium catalyst to establish the effect of the rhodium precursor, temperature, ligand-to-rhodium ratio, and hydrogen and carbon monoxide partial pressures on the activity and selectivity of the reaction. The performance of the SP modified reaction was compared to the performance of unmodified and triphenyl phosphine (PPh 3) modified reactions. In the case of the SP modified reaction, the rhodium precursor had a significant effect on the conversion, but only a minor effect on the selectivity. In contrast to the PPh 3 ligand, the regioselectivity of reaction did not change as the temperature and the total pressure were varied with a fixed [H 2]/[CO] ratio. Unfortunately, the deactivation of the catalyst was strong at elevated temperatures. The increase in hydrogen partial pressure increased the conversion of MMA but had no effect on the selectivity. A minimum carbon monoxide pressure was needed to achieve good chemo- and regioselectivities. The increase in catalyst concentration accelerated the rate of parallel hydrogenation.

Atom Transfer Radical Polymerization of Methyl Methacrylate by Silica Gel Supported Copper Bromide/Multidentate Amine

A silica gel support system for the copper bromide−hexamethyltriethylenetetramine (HMTETA) complex was successfully developed for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in toluene. The supported complex mediated a living polymerization of MMA, yielding polymers with controlled molecular weights and narrow molecular weight distributions. The MMA concentration had significant influence on the polymerization behavior. At 33% MMA concentration, the polymerization catalyzed by CuBr−HMTETA/silica gel followed typical first-order kinetics with respect to the monomer. But at 50% MMA, the polymerization significantly deviated from the first-order kinetics after the MMA conversion reached 30%. The supported catalysts were recycled for second and third uses. The recycled catalysts remained 80% active in the second use and 50% in the third use relative to their initial activity. The recycled catalysts had even better controllability over the polymerization. The molecular weights of PMMA produced agreed with the predicted values, and the polydispersities were less than 1.2.

Controlled radical polymerization of methyl methacrylate in the presence of carbon tetrachloride, metallic copper and 2,2′-bipyridine or 1,10-phenanthroline

The polymerization behaviors of methyl methacrylate (MMA) in the presence of carbon tetrachloride (CCl 4), metallic copper powder (Cu 0) and 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen) in p-xylene at 95°C was examined. In both systems of Cu 0/bpy/CCl 4/MMA/ p-xylene and Cu 0/phen/CCl 4/MMA/ p-xylene, the `living' nature of these two systems was demonstrated by the linear relationship between the MMA conversion and the number-average molecular weight ( M n) of the produced poly(methyl methacrylate) (PMMA) as well as reaction time and ln[M] o/[M]. Furthermore, the polydispersity index of the PMMA obtained in the former case was smaller than that in the latter case. In the Cu 0/bpy/CCl 4/MMA/ p-xylene system, with decreasing the amount of Cu 0, the polymerization rate decreased and the polydispersity of the obtained PMMA increased, while the M n of PMMA was still close to the calculated one by assuming that one molecule of CCl 4 initiates only one polymer chain.

Controlled radical polymerization of methyl methacrylate in the presence of CuX/phen complexes and alkyl halides

The polymerization behaviour of methyl methacrylate (MMA) in p-xylene in the presence of CuCl/L [L=1,10-phenanthroline (phen) or 4,7-diphenyl-1,10-phenanthroline (DPP)] and tetrachlorocarbon has been studied. For the CCl 4/CuCl/phen/MMA/ p-xylene system, the linear relationship between the number-average molecular weight of the resulting poly(methyl methacrylate) (PMMA) and MMA conversion, as well as between ln[M] 0/[M] and time, demonstrate the `living' nature of this system. When phen is replaced by DPP the polymerization becomes slower, but the molecular weight and molecular weight distribution are better controlled. The stereochemistry of PMMA synthesized in the CCl 4/CuCl/DPP/MMA/ p-xylene system indicates that the MMA monomer adds to the living polymer chain end in an atactic fashion.

Modeling Insight into the Diffusion-Limited Cause of the Gel Effect in Free Radical Polymerization

The molecular-level cause of the gel effect in free radical polymerization, associated with a decrease in the termination rate parameter with increasing conversion, is studied by experimental and modeling approaches. The predictive Vrentas−Duda free volume theory serves as a basis for modeling as it handles quantitatively the temperature and polymer concentration dependencies of monomer diffusion. The polymer concentration (c) dependencies of various diffusional processes fit an expression of the form [Dm(c)/Dm(0)]ξx,m, where Dm is the monomer diffusion coefficient and ξx,m expresses the power-law dependence of the diffusional process of interest (x) relative to that of monomer (m). Relevant values of ξx,m vary from ∼ 0.8 for segmental mobility, to ∼1−2 or 3 for oligomeric diffusion, to ∼ 3.0−3.5 for unentangled polymer diffusion, and to ∼ 9.5−10 for entangled polymer diffusion. If the very high conversion regime, where issues unrelated to the origin of the gel effect add unnecessary complications, is avoided, the modeling of conversion−time data requires only that the polymer concentration dependence of the termination reaction, caused by a diffusional process cited above, must be taken into account. Comparison of ξx,m values needed to fit various methyl methacrylate conversion−time data (values of 1.1−5.0 were required, increasing with increasing molecular weight of the polymer produced) with those needed for different diffusion types indicates that termination is governed by diffusion of the shortest radical chains present in significant number. In contrast to some “short−long” termination theories that commonly distinguish “short” and “long” as unentangled and entangled, this study finds that entanglements are irrelevant in distinguishing “short” from “long”. Styrene polymerizations yield ξx,m values substantially below 1. This is ascribed to chain transfer, supported by the fact that methyl methacrylate systems with chain transfer agent show similar suppressed gel effect behavior. The very low ξx,m values result in part from the reduced polymer concentration dependence of kt associated with the highly mobile short radical chains obtained in chain transfer reactions. While systems with significant chain transfer must be studied further, this modeling approach should serve as a robust basis for a more complete description of termination under various conditions.

UV and fluorescence characterization of styrene and methyl methacrylate polymerization

AbstractPolymerization of styrene and methyl methacrylate (MMA) were studied by UV and fluorescence spectroscopic techniques. Using a sharp decrease in the extinction coefficient at 250 nm and the fluorscence quantum yield at 308 nm of styrene following polymerization, styrene conversion in solution polymerization by UV and fluorescence measurements were found to correlate well with IR results monitoring the disappearance of vinyl groups, at three different temperatures (65, 70, and 75°C). The activation energy of about 6 kcal/mol was obtained. Using the decrease in UV absorbance of MMA during polymerization, solution polymerization of MMA was studied and compared with IR results. Due to the solvent absorbance, the UV method underestimates the conversion to a certain extent. When a small amount of styrene is added in MMA polymerization as a reactive extrinsic comonomer, the conversion of styrene measured by fluorescence is found to be faster than MMA, due to the characteristic reactivity ratios of MMA and styrene. The correlation curve could be used to estimate MMA conversion from styrene fluorescence, providing a method more sensitive than the viscosity‐dependent fluorescence probe technique. Bulk polymerization of styrene was studied by bifurcated fiber‐optic fluorescence. Due to self‐quenching, little fluorescence of styrene is observed up to 75% conversion, but increases sharply from 75 to 85% conversion, followed by a drastic decrease during the last 15% conversion. In comparison to other methods of following vinyl polymerization such as refractive index, density, and gel permeation chromatography, these spectroscopic techniques provide real‐time in situ capability as well as better sensitivity, especially in the later stages of polymerization. © 1995 John Wiley & Sons, Inc.

Isospecific Polymerization of Methyl Methacrylate Initiated by Chiral Zirconocenedimethyl/Ph3CB(C6F5)4 in the Presence of Lewis Acid

Polymerization of methyl methacrylate (MMA) was conducted with the catalyst systems of rac-Et(Ind) 2 Zr(CH 3 ) 2 /Ph 3 CB(C 6 F 5 ) 4 , rac-Et(IndH 4 ) 2 Zr(CH 3 ) 2 /Ph 3 CB(C 6 F 5 ) 4 , and rac-Me 2 Si(Ind) 2 Zr(CH 5 ) 2 /Ph 3 CB(C 6 F 5 ) 4 . These catalysts only were found to be inactive. However, the addition of suitable Lewis acids like alkylzinc and alkylaluminum compounds gave highly isotactic PMMA. The isotactic pentad [mmmm] in PMMA as well as the propagation rate constant (k p ) depended significantly upon the zirconocene compounds. Both the microstructure ([mmmm]) and propagation rate constant (k p ) increased in the following order. Me 2 Si(Ind) 2 CH 2 CH 3 > (CH 2 ) 3 CH 3 . When the polymerization was initiated by the rac-Et(Ind) 2 Zr(CH 3 ) 2 /Ph 3 CB(C 6 F 5 ) 4 /Zn(C 2 H 4 CH=CH 2 ) 2 catalyst system at 0°C in toluene, the molecular weight of PMMA increased in proportion to the conversion of MMA. The increase of temperature from 0 to 80°C caused a decrease in isotactic pentad content by approximately 10%. The isotactic polymerization of MMA was revealed to proceed by an enantiomorphic site-controlled mechanism

ヒドロキシアパタイト存在下におけるセリウム （ＩＶ） イオンによるメタクリル酸メチルの重合

Polymerization of methyl methacrylate (MMA) initiated by Ce (IV) ion was studied in the presence of hydroxyapatite (HAP) and H2SO4 in aqueous solution at 30°C. The rate of polymerization (Rp) was proportional to [Ce(IV)]1.91. The effect of H2SO4 was also studied in the concentration range from 0 to 7.65×10-3mol/l.The maximum conversion of MMA was given around at 3.6×10-3mol/l of H2SO4. The degree of polymerization of the free homopolymer (PMMA) was 4000-8000 and the efficiency of grafting of PMMA onto HAP was 19-25%.

Effect of Rh(III) and Ru(II) complexes in the polymerization of vinyl monomers initiated by charge transfer mechanism

AbstractThe initiation of polymerization of vinyl monomers such as methyl methacrylate (MMA) and methyl acrylate (MA) by a charge transfer complex formed between n‐butylamine(nBA) and carbon tetrachloride (CCl4) in dimethylsulfoxide (DMSO) at 30°C is slow. The effect of the dimethylsulfoxide complexes of Rh(III) and Ru(II) on the polymerization of MMA and MA in the presence of nBA, and CCl4 in DMSO has been studied. The rate of polymerization and percent conversion of the MMA and MA at 30°C are evaluated at the critical concentration of the metal complexes. At the critical range of the metal complex concentrations, both Rp, and percent conversion of MMA and MA were found to be highest. However, above and below the critical concentrations, Rp and percent conversion of the monomers were found to decrease. A suitable mechanism for the polymerization has been proposed.