Anionic Copolymerizations of Acrolein with Methyl Vinyl Ketone and Acrylamide by Imidazole

The anionic copolymerizations of acrolein (AL) with methyl vinyl ketone (MVK) and acrylamide (AAm) in the presence of imidazole (Im) as an initiator have been studied in tetrahydrofuran at 0°C. The AL-MVK copolymers were found to be composed of vinyl polymer with one Im group attached and having an aldehyde and a carbonyl side chain. The monomer reactivity ratio was determined from a Fineman-Ross plot as r₁ = 2.02 and r₂ = 0.06. On the other hand, the AL-AAm copolymer were found to be composed of polymer units of 1,2 and 1,4 addition polymerization of AAm. These observations might be explained by the intermolecular hydrogen transfer mechanism of AAm. The polymerization mechanisms were discussed on the basis of these copolymerization results.     

Photodegradation in solution of copolymers of methyl vinyl ketone and methyl isopropenyl ketone with methyl methacrylate

Copolymers of methyl vinyl ketone (MVK) and methyl isopropenyl ketone (MIK) with methyl methacrylate (MMA), have been prepared covering the whole composition range. Reactivity ratios have been estimated as follows: MMA/MVK, r_MMA = 0·63 ± 0·2, r_MVK = 0·53 ± 0·2; MMA/MIK, r_MMA = 0·98 ± 0·2, r_MIK = 0·69 ± 0·2. Number average molecular weights have been measured during the course of photodegradation under 253·7 nm radiation in methyl acetate solution and rates of chain scission calculated. In each system the copolymers are less stable than the corresponding homopolymers, the rate passing through a maximum at 20–30% ketone content. These results have been discussed from a mechanistic point of view.     

Effect of solvent in radical polymerization of butadiene 1-carboxylic acid

The radical polymerization and copolymerization of butadiene 1-carboxylic acid (Bu-1-Acid) were studied in a variety of the electron-donor solvents such as dimethylformamide (DMF), tetrahydrofuran (THF), methyl ethyl ketone (MEK), acetonitrile (ACN), and benzene (BZ) using AIBN as an initiator at 50°C. Under these conditions, the polymerization rate of Bu-1-Acid increased in the order, DMF < THF < MEK < ACN < BZ in the various solvents. In copolymerization with styrene [M₂] and acrylonitrile [M₂], the monomer reactivity ratio r₁ increased and r₂ decreased in the same order. Moreover, it was found that Alfrey-Price Q-e value of Bu-1-Acid increased depending on solvent in the order DMF < THF < MEK < ACN < BZ. These variations were correlated to the electron-donating power (Δvcm^?) of the solvents used and are discussed on the basis of the solvation of Bu-1-Acid into the solvent. Also, it was found that the microstructures of these polymers were always trans-1,4 and did not change with the solvent used.     

Radical Copolymerizability of Acrylamide Derivatives with Methyl Vinyl Ketone

Radical copolymerization of methyl vinyl ketone (MVK, M₁) with acrylamide (AAm) and its derivatives, such as methacrylamide (MAAm) and N,N′ -dimethylacrylamide (DMAAm), was carried out in dioxane or ethanol using α,α - azobisisobutylonitrile as the initiator at 60°C under vacuum. The monomer reactivity ratios found in dioxane were as follows: ri = 1.06, r₂ = 6.41 for the MVK-AAm system; r₁ = 0.29, r₂ = 3.05 for the MVK-MAAm system; and r₁ = 0.95, r₂ = 0.26 for the MVK-DMAAm system. The n and r₂ values obtained in ethanol were as follows: r₁ = 0.88, r₂ = 1.18 for the MVK-AAm system; and r₁ = 0.37, r₂ = 2.04 for the MVK-MAAm system. Q₂ and e₂ values of AAm derivatives in dioxane were estimated to be 3.03 and 1.04 for MAAm and 2.15 and 1.11 for DMAAm, respectively. The Q₂ and e₂ values of MAAm in ethanol were estimated to be 2.67 and 1.21, respectively. Based on these results, the alternating copolymerizability depends on the interaction of monomer-monomer, and the strong solvent effect depends on the radical copolymerization of the AAm derivatives.     

TPD/MS studies of the interaction of simple ketones with ZSM-5 zeolites

Temperature-programmed desorption (TPD) of products formed by the interaction of simple ketones with HZSM-5 zeolites has been studied mass spectrometrically. Acetone (MMK), methyl ethyl ketone (MEK) and diethyl ketone (EEK) were preadsorbed on HZSM-5 and NaZSM-5 zeolites at room temperature in amounts ranging from 0.04 to 2 mmol g⁻¹. It was shown that the qualitative composition of the products did not depend on the amount of preadsorbed ketone; the reactivity of the ketones increased from MMK to EEK. The conversion of MMK on HZSM-5 proceeded via acid intermolecular condensation, which could not take place on NaZSM-5. In the transformation of MEK, intramolecular dehydration played a role in the interaction, along with the above condensation mechanism; in this case NaZSM-5 also exhibited some activity. The mechanism of intramolecular dehydration prevailed in the reaction with EEK where, unlike NaZSM-5, HZSM-5 caused further conversion of the dehydrated products. The experiments with deuterated ketones, MMK-d₆ and MEK-d₅, have shown involvement of zeolitic hydrogen in the reaction complexes.     

Reversible addition-fragmentation chain transfer radical copolymerization of β-pinene and methyl acrylate

The feasibility of radical copolymerization of β-pinene and methyl acrylate (MA) was clarified for the first time. The monomer reactivity ratios were evaluated by Fineman-Ross, Kelen-Tudos and non-linear methods, respectively. The obtained values were r_β-pinene ∼ 0 and r_MA ∼ 1.3, indicating that the copolymerization led to polymers rich in methyl acrylate units and randomly alternated by single β-pinene unit. The addition of Lewis acid Et₂AlCl to the AIBN-initiated copolymerization enhanced the incorporation of β-pinene. Furthermore, the possible controlled copolymerization of β-pinene and MA was then attempted via the reversible addition-fragmentation transfer (RAFT) technique. The copolymerization (f_β-pinene = 0.1) using 1-methoxycarbonyl ethyl dithiobenzoate (MEDB) as a RAFT agent gave copolymers with lower molecular weight and narrower molecular weight distribution. However, the presence of MEDB strongly retarded the copolymerization. Thus a new RAFT agent 1-methoxycarbonyl ethyl phenyldithioacetate (MEPD), which gives a less stable macroradical intermediate than MEDB, was synthesized and introduced to the copolymerization. As anticipated, a much smaller retardation was observed. Moreover, the copolymerization displayed a somewhat controlled features within a certain overall conversion (<∼40%).     

Isospecific copolymerization of styrene and a styrene‐terminated polyisoprene macromonomer with the Ni(acac)2/MAO catalyst

The copolymerization of styrene (St) with a styrene‐terminated polyisoprene macromonomer (SIPM) by a nickel(II) acetylacetonate [Ni(acac)₂] catalyst in combination with methylaluminoxane (MAO) was investigated. A SIPM with a high terminal degree of functionalization and a narrow molecular weight distribution was used for the copolymerization of St. The copolymerization proceeded easily to give a high molecular weight graft copolymer. After fractionation of the resulting copolymer with methyl ethyl ketone, the insoluble part had highly isotactic polystyrene in the main chain and polyisoprene in the side chain. Lowering the MAO/Ni molar ratio and the polymerization temperature were favorable to producing isospecific active sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1241–1246, 2000     

Radical copolymerization of crotonyl compounds with styrene

The monomer reactivity ratios for the radical copolymerization of crotononitrile (CN), methyl crotonate (MC), and n-propenyl methyl ketone (PMK) with styrene (St) were measured at 60°C. in benzene and little penultimate unit effect was shown for these systems. The values obtained were: St–CN, r₁ = 24.0, r₂ = 0; St–MC, r₁ = 26.0, r₂ = 0.01; St–PMK, r₁ = 13.7, r₂ = 0.01. The rate of copolymerization and the viscosity of the copolymer decreased markedly as the molar fraction of the crotonyl compound in the monomer mixture increased. The Q–e values were also calculated to be as follows: CN, e = 1.13, Q = 0.009; MC, e = 0.36, Q = 0.015; PMK, e = 0.61, Q = 0.024. A linear relationship was obtained between the e values of the crotonyl compounds and their Hammett constants σ_m.     

Amphoteric initiators suitable for emulsifier-free emulsion polymerization and the properties of the resulting latices

The soap-free emulsion polymerizations of styrene (St) and acrylamide (AAm) or methyl methacrylate (MMA) were carried out in the presence of three kinds of amphoteric initiators, and the polymerization kinetics and the colloidal properties of the latices produced were emphatically investigated. It was found that the number of carbon atoms between the amidino and carboxyl groups in each initiator exhibited an appreciable effect on the dissociation as well as on the solubility of the initiator in water, and therefore, that the properties of the colloidal particles depended on the structure of the initiators used. All the copolymerization runs, except for the polymerization using 2,2′-azobis(N-(2-caboxyethyl)-2-methylpropionamidine) under a strongly alkali condition, gave amphoteric latices, which indicated higher critical flocculation concentrations at lower or higher pHs than at a medium pH. The surface charge density measured by titration for poly(St/MMA) particles was about 3–10 times as high as that for the poly(St/AAm) ones, though these were prepared under the same conditions other than the monomer composition. The influence of the polymerization pH on both the polymerization rate and the surface charge density of the resulting latices was negligible even if the constants of the decomposition rate and the dissociation of the amphoteric initiators strongly depended on the pH of the medium. Received: 28 July 2000 Accepted: 1 November 2000     

Radical-initiated homo- and copolymerizations of methacryloyl fluoride

The kinetics of methacryloyl fluoride (MAF) homopolymerization was investigated in methyl ethyl ketone (MEK) with azobis(isobutyronitrile) as initiator. The rate of polymerization (R_p) followed the expression R_p = k[AIBN]^0.55[MAF]^1.18. The overall activation energy was calculated as 74.4 kJ/mol. The relative reactivity ratios of MAF(M₂) copolymerization with styrene (r₁ = 0.083, r₂ = 0.14), and methyl methacrylate (r₁ = 0.48, r₂ = 0.81) in methyl ethyl ketone were obtained. Application of the Q–e scheme (in styrene copolymerization) led to Q = 2.22 and e = 1.31. The glass transition temperature (T_g) of poly(MAF) was 90°C by thermomechanical analysis. Thermogravimetry of poly(MAF) showed a 10% weight loss of 228°C in air.     

Kinetics and mechanism of the oxidation of some aliphatic ketones by n-bromoacetamide in acidic media

Kinetics of the oxidation of methyl ethyl ketone (MEK) and diethyl ketone (DEK) by N-bromoacetamide (NBA) have been studied in perchloric acid media in the presence of mercuric acetate. A zero order dependence to NBA and a first-order dependence to both ketones and H⁺ have been observed. Acetamide, mercuric acetate and sodium perchlorate additions have negligible effect while addition of acetic acid has a positive effect on the reaction rate. A solvent isotope effect (K₀D₂O/k₀H₂O = 2.–.4 and 2.2-2.5 for MEK and DEK, respectively) has been observed at 40°. Kinetic investigations have revealed that the order of reactivity is MEK > DEK. The rates were determined at four different temperatures and the activation parameters were evaluated. The main product of the oxidation is the corresponding 1,2-diketone. A suitable mechanism consistent with the above observations has been proposed.     

水分散体系中苯乙烯和甲基丙烯酸甲酯梯度共聚物的合成与表征

以2-溴代异丁酸乙酯(EBiB)为引发剂,CuBr/CuBr₂/1,10-邻二氮菲(phen)为复合催化剂,十二烷基磺酸钠(SLS)为乳化剂,考察了水分散体系中苯乙烯(St)和甲基丙烯酸甲酯(MMA)的原子转移自由基共聚合的可控性和相对反应活性.在此基础上,通过反应进料法在水分散体系中进行了St和MMA的梯度共聚合,反应表现出“活性”聚合的特征,即所得共聚物的数均分子量随着单体转化率的增加而增大,分子量分布较窄(M_w/M_n<1.50).用¹HNMR跟踪分析了聚合反应过程中共聚物微观组成的变化规律,结果表明,共聚物链中MMA链节的累积含量和瞬时含量都随着共聚物相对链长的增加而增加,即随着聚合物相对链长的增加共聚物的微观组成从St链节占主导地位逐渐变化为以MMA链节占主导地位,表明确实形成了St和MMA的梯度或渐变共聚物.     

Synthesis and Characterization of Novel Methacrylic Copolymers: Determination of Monomer Reactivity Ratios

A new methacrylic monomer, 4‐nitro‐3‐methylphenyl methacrylate (NMPM) was prepared by reacting 4‐nitro‐3‐methyl phenol dissolved in methyl ethyl ketone (MEK) in the presence of triethylamine as a catalyst. Copolymerization of NMPM with methyl methacrylate (MMA) has been carried out in methyl ethyl ketone (MEK) by free radical solution polymerization at 70±1°C utilizing benzoyl peroxide (BPO) as initiator. Poly (NMPM‐co‐MMA) copolymers were characterized by FT‐IR, ¹H‐NMR and ¹³C‐NMR spectroscopy. The molecular weights (M_w and M_n) and polydispersity indices (M_w/M_n) of the polymers were determined using a gel permeation chromatograph. The glass transition temperatures (T_g) of the copolymers were determined by a differential scanning calorimeter, showing that T_g increases with MMA content in the copolymer. Thermogravimetric analysis of the polymers, performed under nitrogen, shows that the stability of the copolymer increases with an increase in NMPM content. The solubility of the polymers was tested in various polar and non‐polar solvents. Copolymer compositions were determined by ¹H‐NMR spectroscopy by comparing the integral peak heights of well separated aromatic and aliphatic proton peaks. The monomer reactivity ratios were determined by the Fineman‐Ross (r₁ =7.090:r₂=0.854), Kelen‐Tudos (r₁=7.693: r₂=0.852) and extended Kelen‐Tudos methods (r₁=7.550: r₂= 0.856).     

Rhodium-catalyzed α-methylthiolation reaction of unactivated ketones using 1,2-diphenyl-2-methylthio-1-ethanone for the methylthio transfer reagent

In the presence of catalytic amounts of RhH(PPh₃)₄, 1,2-bis(diphenylphosphino)ethane (dppe), and dimethyl disulfide, ketones without α-activating groups were α-methylthiolated with 1,2-diphenyl-2-methylthio-1-ethanone giving α-methylthio ketones. The reaction of unsymmetrical ketones proceeded at the more substituted carbons. The initial formation of kinetic α-methylthiolated products followed by their rearrangement to thermodynamic products was observed in the reaction of α-phenyl ketones. Aldehydes, phenylacetate, and phenylacetonitrile were also α-methylthiolated under these conditions.     

Effect of nanoclay and macroinitiator on the kinetics of atom transfer radical homo- and copolymerization of styrene and methyl methacrylate initiated with CCl3-terminated poly (vinyl acetate) macroinitiator

Effect of nanoclay on the kinetics of atom transfer radical bulk homo- and copolymerization of styrene (St) and methyl methacrylate (MMA) initiated with CCl₃-terminated poly (vinyl acetate) macroinitiator at 90 °C was investigated. CuCl/PMDETA was used as a catalyst system. Results showed that nanoclay significantly enhances the homopolymerization rate of MMA. It was attributed to the activated conjugated CC bond of MMA monomer via interaction between the carbonyl group of MMA monomer and the hydroxyl moiety (AlOH) of nanoclay as well as to the effect of nanoclay on the dynamic equilibrium between the active (macro)radicals and dormant species. Homopolymerization rate of St (a noncoordinative monomer with nanoclay) decreased slightly in the presence of nanoclay. It could be explained by inserting of a portion of macroinitiator into the clay galleries, where no sufficient St monomer exists due to the low compatibility or interaction of St monomer with nanoclay to react with the macroinitiator. Controlled/living characteristic of all the reactions were confirmed by GPC results. More reliable reactivity ratios of the St and MMA in the presence of nanoclay were calculated by using the cumulative average copolymer composition at the moderate to high conversion to be r_St = 0.290 ± 0.082, r_MMA = 0.443 ± 0.093 (extended Kelen-Tudos method) and r_St = 0.293 ± 0.071, r_MMA = 0.447 ± 0.080 (Mao-Huglin method). Results indicated that the rate of incorporation of MMA comonomer into the copolymer increases in the presence of nanoclay, verifying the existence of interaction between the carbonyl group of MMA comonomer and the hydroxyl moiety of nanoclay. It was found that in the presence of nanoclay, tendency of the random copolymerization of St and MMA toward an alternating copolymerization increases.     

ZrOCl2·8H2O: an efficient Lewis acid catalyst for the one-pot multicomponent synthesis of β-acetamido ketones

Aromatic aldehydes were reacted in one-pot with enolisable ketones, acetonitrile and acetyl chloride at ambient temperature in the presence of ZrOCl₂·8H₂O to furnish the corresponding β-acetamido ketones in very good to excellent yields. X-ray crystallographic analysis of one anti-β-acetamido ketone exhibited a two-dimensional supramolecular framework by a combination of N-H?O, C-H?O and C-H?π (arene) hydrogen bonds.     

Copolymerization reactivity of poly(methyl methacrylate) macromer

Poly(methyl mehtacrylate)(PMMA) macromers with several vinyl groups at both chain ends were synthesized by the mechanical scission reaction of the main chain in the presence of p-divinylbenzene(p-DVB). The radical copolymerization of this macromer with styrene(St) or MMA was carried out in benzene at 60°C and the reactivity ratio of both monomers (r₂) was calculated from a kinetic scheme of copolymerization. As a result, the effect of molecular weight and concentration of macromers was not observed in both copolymerization systems. The value of r₂, however, decreased as the number of end vinyl groups in a macromer (N) increased. These results are discussed in some detail as we describe the construction of the kinetic model of copolymerization.     

Syn/anti isomerization of 2,4-dinitrophenylhydrazones in the determination of airborne unsymmetrical aldehydes and ketones using 2,4-dinitrophenylhydrazine derivation

Aldehydes and ketones readily react with 2,4-dinitrophenylhydrazine (2,4-DNPH) to form the corresponding hydrazones. This reaction has been frequently used for the quantification of airborne carbonyl compounds. Since unsymmetrical aldehydes and ketones are known to form isomeric 2,4-dinitrophenylhydrazones (syn/ anti-isomers), the influence of isomerization on the practicability and accuracy of the 2,4-DNPH-method using 2,4-dinitrophenylhydrazine-coated solid sorbent samplers has been studied with three ketones (methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), and methyl isobutyl ketone (MIBK)). With all three ketones the reaction with 2,4-DNPH resulted in mixtures of the isomeric hydrazones which were separated by HPLC and GC and identified by mass spectroscopy and ¹H nuclear magnetic resonance spectroscopy. The isomers show similar chromatographic behaviour in HPLC as well as in GC, thus leading to problems in quantification and interpretation of chromatographic results.     

Synthesis of poly(methyl methacrylate-co-styrene)-block-polysulfide-block-poly(methyl methacrylate-co-styrene) copolymers by free radical polymerization combined with oxidative coupling

Poly(methyl methacrylate-co-styrene)-block-polysulfide-block-poly(methyl methacrylate-co-styrene) triblock copolymers were synthesized for the first time by the free radical copolymerization of methyl methacrylate (MMA) and styrene (St) in the presence of a thiocol oligomer as a chain transfer agent, followed by chemical oxidation of the remaining SH-end groups. The apparent chain transfer constant of the thiocol SH groups in the copolymerization reaction was estimated from the rate of consumption of the thiol groups versus the overall rate of consumption of the monomers (C_T = 1.28). Based on this value, the chain transfer constant of the thiocol SH groups in St polymerization was calculated . The triblock copolymers synthesized were characterized by SEC and ¹H NMR measurements.     

Copolymerization and Copolymers of 2,4,5-Tribromostyrene with Styrene and Acrylonitrile

Abstract

2,4,5-Tribromostyrene (TBSt) was copolymerized with styrene (St) or acrylonitrile (AN) in toluene solution using 2,2′-azobisisobutyronitrile as free radical initiator. The copolymerization reactivity ratios were found to be for the system TBSt/St r ₁ = 1.035 ± 0.164 (TBSt) and r ₂ = 0.150 ± 0.057 (St), and for the system TBSt/AN r ₁ = 2.445 ± 0.270 (TBSt) and r ₂ = 0.133 ± 0.054 (AN). The e and Q values were also calculated. The initial copolymerization rate, R _p, for both systems linearly increases as the content of TBSt in the monomer mixture increases. However, these values are somewhat higher when AN was used as a comonomer. A similar behavior has also been established for the course of the copolymerization reactions to high conversion. The resulting copolymers and TBSt-homopolymer show similar thermal stabilities of polystyrene. However, the glass transition temperature increases markedly with increasing TBSt content.