Makiko Seno

Kinetic and ESR studies on radical polymerization of methyl methacrylate in the presence of fullerene

The effect of fullerene (C60) on the radical polymerization of methyl methacrylate (MMA) in benzene was studied kinetically and by means of ESR, where dimethyl 2,2′-azobis(isobutyrate) (MAIB) was used as initiator. The polymerization rate (Rp) and the molecular weight of resulting poly(MMA) decreased with increasing C60 concentration ((0–2.11) × 10−4 mol/L). The molecular weight of polymer tended to increase with time at higher C60 concentrations. Rp at 50°C in the presence of C60 (7.0 × 10−5 mol/L) was expressed by Rp = k[MAIB]0.5[MMA]1.25. The overall activation energy of polymerization at 7.0 × 10−5 mol/L of C60 concentration was calculated to be 23.2 kcal/mol. Persistent fullerene radicals were observed by ESR in the polymerization system. The concentration of fullerene radicals was found to increase linearly with time and then be saturated. The rate of fullerene radical formation increased with MAIB concentration. Thermal polymerization of styrene (St) in the presence of resulting poly(MMA) seemed to yield a starlike copolymer carrying poly(MMA) and poly(St) arms. The results (r1 = 0.53, r2 = 0.56) of copolymerization of MMA and St with MAIB at 60°C in the presence of C60 (7.15 × 10−5 mol/L) were similar to those (r1 = 0.46, r2 = 0.52) in the absence of C60.

Radical polymerization of vinyl monomers in the presence of ethyl α-benzene- and α-p-toluenesulfonylmethylacrylates

Abstract Ethyl α-benzene-(EBSA) and α-toluenesulfonylmethylacrylate (ETSA) were found to show no homopolymerizability but to act as effective chain transfer reagents in radical polymerizations of methyl methacrylate (MMA), styrene (St) and n -butyl acrylate (BA), being conjugative monomers. The estimated chain transfer constants ( C T ) are as follows; C t (EBSA) = 0.73(50 °C) and 0.72(60 °C) for MMA, 4.80(50 °C) and 4.21(60 °C) for St, 1.78(50 °C) and 1.69(60 °C) for BA; C T (ETSA) = 1.09(60 °C) for MMA, 6.80(60 °C) for St, 2.31(60 °C) for BA. i.r. and 1 H-NMR spectra of poly(MMA) and poly(St) formed in the presence of EBSA and ETSA are consistent with the view that the polymers bear a CC bond at one terminal and an arenesulfonyl group at the other. These findings indicate that the ethyl α-arenesulfonylmethylacrylates undergo chain transfer reaction via an addition-fragmentation mechanism.

Kinetic and ESR studies on radical polymerization. Radical polymerization of diisopropyl itaconate

Abstract The polymerization of diisopropyl itaconate (DIPI) initiated with dimethyl 2,2′-azobisisobutyrate(MAIB) was investigated kinetically in benzene. The polymerization rate ( R p ) was expressed by R p = k [MAIB] 0.46 [DIPI] 1.6 at 50°. The overall activation energy of the polymerization was calculated to be a low value of 60.2 kJ/mol. Rate constants of propagation ( k p ) and termination ( k 1 ) were estimated different polymerization conditions, using the ESR-determined concentrations of the propagating polymer radical. The k p value (2.4–2.9 1/mol · sec) at 50° shows a little increase with monomer concentration. The k 1 value (1.8–4.9 × 10 4 1/mol · sec) was fairly dependent on the chain-length of the propagating polymer radical, which is mainly responsible for the high dependence of R p on the monomer concentration. Activation energies of initiation ( E i ), propagation ( E p ) and termination ( E t ) were also determined; E i = 129.1 kJ/mol, E p = 28.5 kJ/mol, E t , = 66.1 kJ/mol. The large apparent activation energy of termination is a main origin of the low overall activation energy of the polymerization. Copolymerization of DIPI ( M 1 ) with St ( M 2 ) was also examined at 50° in benzene. The following copolymerization parameters were obtained according to the Kelen-Tudos method; r 1 = 0.11, r 2 = 0.56, Q = 0.47, e = + 0.87. Using the above results, the rate constants of cross-propagations in the copolymerization were estimated.

Effect of fullerene on radical polymerization of vinyl acetate

The effect of fullerene (C60) on the radical polymerization of vinyl acetate (VAc) with dimethyl 2,2′-azobisisobutyrate (MAIB) in benzene was investigated kinetically and by means of ESR. C60 was found to act as an effective inhibitor in the present polymerization. All C60 molecules used were incorporated into poly(VAc) during polymerization. The relationship of induction period and initiation rate reveals that a C60 molecule can trap 15 radicals formed in the polymerization system. The polymerization rate (Rp) after the induction period is given by Rp = k [MAIB]0.6 [VAc]2.0 (60 °C), which is similar to that observed in the absence of C60. Stable fullerene radical (C) was observed in the polymerization system by ESR. The C concentration increased with time and was then saturated. The saturation time well corresponds to the induction period observed in the polymerization. About 20% of C60 molecules added could survive as stable C.

Solvent effects on the radical polymerization ofN-dodecylmaleimide

SummaryThe rate of homogeneous polymerization of N-dodecylmaleimide (DMIm) with dimethyl 2,2′-azobisisobutyrate depended significantly on the kind of solvents used. The polymerization systems involved ESR-observable propagating poly(DMIm) radical. The rate constants of propagation(kp) and termination(kt) were determined at 50°C in various solvents. The kp value was smaller in aromatic solvents than in aliphatic ones. The Hammetts plot of kp against σ-value of the substituents on the aromatic solvents showed that kp took higher values in the solvents with either electron-accepting or donating substituents. The solvent effects on kp seemed to stem from complexion of poly(DMIm) radical with solvents.

Kinetic study on the radical Polymerization of 2-methacryloyloxyethyl phosphorylcholine

Polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) was kinetically investigated in ethanol using dimethyl 2,2′-azobisisobutyrate (MAIB) as initiator. The overall activation energy of the homogeneous polymerization was calculated to be 71 kJ/mol. The polymerization rate (Rp) was expressed by Rp = k[MAIB]0.54±0.05 [MPC]1.8±0.1. The higher dependence of Rp on the monomer concentration comes from acceleration of propagation due to monomer aggregation and also from retardation of termination due to viscosity effect of the MPC monomer. Rate constants of propagation (kp) and termination (kt) of MPC were estimated by means of ESR to be kp = 180 L/mol · s and kt = 2.8 × 104 L/mol · s at 60 °C, respectively. Because of much slower termination, Rp of MPC in ethanol was found at 60 °C to be 8 times that of methyl methacrylate (MMA) in benzene, though the different solvents were used for MPC and MMA. Polymerization of MPC with MAIB in ethanol was accelerated by the presence of water and retarded by the presence of benzene or acetonitrile. Poly(MPC) showed a peculiar solubility behavior; although poly(MPC) was highly soluble in ethanol and in water, it was insoluble in aqueous ethanol of water content of 7.4–39.8 vol %. The radical copolymerization of MPC (M1) and styrene (St) (M2) in ethanol at 50 °C gave the following copolymerization parameters similar to those of the copolymerization of MMA and St; r1 = 0.39, r2 = 0.46, Q1 = 0.76, and e1 = +0.51.

Formation of poly(methyl methacrylate) with novel solubility characters in the photopolymerization with bis(cyclopentadienyl)titanium dichloride in a water–methanol mixture

Methyl methacrylate (MMA) was observed to be easily polymerized in the photopolymerization with bis(cyclopentadienyl)titanium dichloride (Cp2TiCl2) in a water–methanol mixture under irradiation of a 15-W fluorescent room lamp. The polymerization proceeded heterogeneously. The rate (Rp) of heterogeneous photopolymerization in a 1 : 1 (v/v) water–methanol mixture at 40°C was apparently given by Rp=k[Cp2TiCl2]0.2 [MMA]2.4. The resulting poly(MMA) was found to contain a tetrahydrofuran (THF)-insoluble part. The separated THF-insoluble part differed significantly from the usual radical poly(MMA) in solubility characters. It is of great interest that the THF-insoluble poly(MMA) was soluble in benzene and toluene, but insoluble in polar solvents, such as ethyl acetate, acetone, methyl ethyl ketone, dimethylformamide, and dimethylsulfoxide. The copolymerization results of MMA and acrylonitrile revealed that the present photopolymerization initiated with Cp2TiCl2 proceeds via a radical mechanism.

Radical polymerization of di-n-butyl itaconate in the presence of Lewis acids

Abstract Intramolecular chain-transfer reaction takes place in polymerizations of itaconates at high temperatures and/or at low monomer concentrations. Polymerizations of di- n -butyl itaconate (DBI) were carried out at 60 °C in the presence of Lewis acids such as scandium trifluoromethansulfonate. Lewis acids hardly influenced the intramolecular chain-transfer reaction in bulk polymerizations. Polymerizations in methanol accompanied transesterification reaction catalyzed by Lewis acids. In polymerizations in toluene, catalytic amounts of Lewis acids were found to be effective in suppressing the intramolecular chain-transfer reaction. Lewis acids showed no significant influences on stereospecificity of polymerization, though isotactic-specificity increase in polymerizations of other acrylate monomers such as methyl methacrylate.

Kinetic and ESR studies on radical copolymerization of p‐tert‐butoxystyrene and di‐n‐butyl maleate in benzene

The copolymerization of p-tert-butoxystyrene (TBOSt) (M1) and di-n-butyl maleate (DBM) (M2) with dimethyl 2,2′-azobisisobutyrate (MAIB) in benzene at 60°C was studied kinetically and by means of ESR spectroscopy. The monomer reactivity ratios were determined to be r1 = 2.3 and r2 = 0 by a curve-fitting method. The copolymerization system was found to involve ESR-observable propagating polymer radicals under practical copolymerization conditions. The apparent rate constants of propagation (kp) and termination (kt) at different feed compositions were determined by ESR. From the relationship of kp and f1 (f1 = [M1]/([M1] + [M2])) based on a penultimate model, the rate constants of five propagations of copolymerization were evaluated as follows; k111 = 140 L/mol s, k211 = 3.5 L/mol s, k112 = 61 L/mol s, k212 = 1.5 L/mol s, and k121 = 69 L/mol s. Thus, a pronounced penultimate effect was predicted in the copolymerization.

Radical Polymerization Behavior of Ethyl α–Naphthoyloxymethylacrylate

Abstract The polymerization of ethyl α-naphthoyloxymethylacrylate (ENMA) with dimethyl 2,2′-azobisisobutyrate (MAIB) in benzene was investigated kinetically and by means of ESR. Polymerization rate (R p) was given by Rp = k[MAIB]0.5[ENMA]1.7 (50°C). The overall activation energy of polymerization was estimated to be 58.4 kJ/mol. The actual polymerization system was found to involve ESR-observable propagating polymer radicals of ENMA. ESR determination of the polymer radical concentration allowed rate constants of propagation (k p) and termination (k t) to be estimated at 60°C: k p = 320 L˙mol−1˙s−1 k t = 3.7 × 105 L˙mol−1˙s−1. Dynamic thermogravimetry showed that the thermal degradation of poly(ENMA) begins at 340°C, and the residue at 500°C was only 4% of the initial polymer. Application of the Kelen–Tudos method to the copolymerization results of ENMA (M1) and styrene (M2) at 50°C gave the following parameters: r 1 = 0.24 ± 0.01 and r 2 = 0.22 ± 0.01 giving Q 1 = 1.14 and e 1 = +0.78.