Aqueous Polymerization of Methyl Methacrylate Initiated by the Mn(lll)-Fructose Redox System

The kinetics of vinyl polymerization of methyl methacrylate initiated by the redox system Mn³-fructose were investigated in aqueous sulfuric acid in the temperature range of 20-25°C, and the rates of polymerization and disappearance of Mn³⁺ were measured. The effect of certain water-miscible organic solvents and certain cationic and anionic surfactants on the rate of polymerization has been investigated. A mechanism involving the formation of a complex between Mn³⁺ and fructose whose decomposition yields the initiating free radical with the polymerization being terminated by the metal ion has been suggested.     

锰(Ⅲ)离子与羧酸或α-羟基羧酸体系引发丙烯酰胺聚合

 锰(Ⅲ)离子可以引发烯类单体自由基聚合。羧酸,α-羟基羧酸对丙烯酰胺聚合有促进作用,其活性顺序为羟基多元羧酸(柠檬酸)>羟基羧酸(乳酸)>羧酸(正丁酸)。测定了在较高酸性([H⁺]=3.0M)的硫酸水溶液中,单独Mn³⁺,Nn³⁺-乙醇酸,Mn³⁺-乳酸引发丙烯酰胺聚合的活化能与动力学方程。     

Aqueous polymerization of acrylonitrile initiated by the Mn3+/citric acid redox system

Kinetics of polymerization of acrylonitrile initiated by the redox system Mn³⁺/citric acid were investigated in aqueous sulphuric acid in the range of 20–25°; initial rates of polymerization and Mn³⁺ disappearance etc. were measured. The effects of certain water miscible organic solvents and certain cationic and anionic detergents on the rate of polymerization have been examined. A mechanism has been suggested involving formation of a complex between Mn³⁺ and citric acid, decomposition of which yields the initiating free radical and with polymerization being terminated by mutual interaction of growing radicals.     

KINETIC STUDY OF GAS-PHASE POLYMERIZATION OF PROPENE BY THE INHIBITION METHOD USING CARBON MONOXIDE

The inhibition method using CO to determine the active center concentration C~* in olefin poly-merization and the kinetics of gas-phase polymerization of propene were studied. The reliabilityof the method when used in gas-phase polymerization of propene is proved and the influencing fac-tor of the method is found to be the "repeating inhibition" of CO to the active centers. The C~*, the rate constant k_P and the activation energy were determined from the experimentalresults. We concluded that the C~* decreases with polymerization time and coincides with the decayrate of the polymerization.     

Kinetics of D,L–Lactide Polymerization Initiated with Zirconium Acetylacetonate

The kinetic of D,L-lactide polymerization in presence of biocompatible zirconium acetylacetonate initiator was studied by differential scanning calorimetry in isothermal mode at various temperatures and initiator concentrations. The enthalpy of D,L-lactide polymerization measured directly in DSC cell was found to be ΔH=−17.8±1.4 kJ mol⁻¹. Kinetic curves of D,L-lactide polymerization and propagation rate constants were determined for polymerization with zirconium acetylacetonate at concentrations of 250–1000 ppm and temperature of 160–220 °C. Using model or reversible polymerization the following kinetic and thermodynamic parameters were calculated: activation energy E_a=44.51±5.35 kJ mol⁻¹, preexponential constant lnA=15.47±1.38, entropy of polymerization ΔS=−25.14 J mol⁻¹ K⁻¹. The effect of reaction conditions on the molecular weight of poly(D,L-lactide) was shown.     

Vinyl polymerization. 403. Polymerization of vinyl monomer initiated with sodium poly-p-vinylphenolate

The polymerization of vinyl monomer initiated by poly-p-vinylphenol (PVPh) in NaOH aqueous solution was carried out at 85°C with shaking. Methyl methacrylate (MMA) was polymerized, whereas styrene and acrylonitrile were not. PVPh, which is dissociated into phenolate form (PVPh^?Na⁺) in NaOH aqueous solution, was effective for the polymerization. The effects of the amounts of MMA, PVPh, NaOH, and H₂O on the conversion of MMA were studied. The rate of polymerization of MMA increased with an increase in the molecular weight of PVPh-Na. The overall activation energy was estimated as 54 kJ mol^?1. The polymerization proceeded through a radical mechanism. The addition of tetra-n-butylammonium bromide increased the rate of polymerization.     

Pentavalent Vanadium-Ascorbic Acid Redox System Initiated Polymerization of Acrylonitrile

Kinetics of polymerization of acrylonitrile initiated by the redox system V⁵⁺ascorbic acid were investigated in aqueous sulfuric acid in the temperature range of 35–50°C, and the rates of polymerization, of V⁵⁺/disappearance, etc. were measured. From the result it was concluded that the polymerization reaction is initiated by an organic free radical arising from the V⁵⁺ - ascorbic acid complex formation followed by subsequent decomposition and terminated by V⁵⁺ions. A suitable kinetic scheme was proposed and the various rate parameters were evaluated.     

Polymerization of Acrylonitrile Initiated by the Thiourea-Mn3+ Redox System

Kinetics of vinyl polymerization initiated by the redox system thiourea-Mn³⁺ were investigated in the temperature range 30–40°C in sulfuric acid, and the rates of polymerization R_p and disappearance of Mn³⁺ have been measured. The effect of certain water-miscible organic solvents and anionic surfactant on the rates of polymerization was investigated. A mechanism involving the formation of a complex between Mn³⁺ and thiourea whose decomposition yields the initiating free radical with the polymerization terminated by mutual intraction of growing radicals is suggested.     

Polymerization of acrylic acid initiated by a hexavalent chromium-organic sulfur compounds reducing agent system

The kinetics of polymerization of acrylic acid initiated by Cr⁶⁺-thiourea, Cr⁶⁺-thioacetamide, Cr⁶⁺-2-aminoethane thiol, Cr⁶⁺-cysteine, and Cr⁶⁺-thioglycollic acid have been studied at 30, 35, and 40°C in nitrogen. The rates of polymerization were measured. Chromic acid alone did not initiate the polymerization under deaerated and un-deaerated conditions. On the basis of the experimental observation of the dependence of the rate of polymerization R_p on various variables, a suitable kinetic scheme is proposed.     

Ring-opening polymerization of macrocyclic aryl ether ketone oligomers containing the 1,2-dibenzoylbenzene moiety

Facile ring-opening polymerization of cyclic aryl ether oligomers containing the 1,2-dibenzoylbenzene moiety to form high molecular weight linear polymers in the presence of a nucleophilic initiator is described. The polymerization can be initiated in the melt in the presence of a nucleophilic initiator such as potassium carbonate, cesium fluoride, and alkali phenoxides. Various alkali phenoxides were investigated as potential nucleophilic initiators. The polymerization reaction rate in the melt increases in the order of K⁺ > Na⁺ > Cs⁺, and in the order of ⁻OPhPhO⁻ > PhO⁻ > PhOPhO⁻ > PhPhO⁻. However, the polymerization in an aprotic dipolar solvent is faster in the presence of cesium phenoxide than in the presence of potassium phenoxide. Polymerization of the cyclic oligomers in solution demonstrates that the ring-opening polymerization proceeds via a chain-growth mechanism and involves a transetherification reaction between linear and cyclic aryl ether oligomers. The ring-chain equilibrium is much more favorable towards linear polymers. Since little or no ring strain exists in the cyclic system, the transetherification reactions are indiscriminate with regards to cyclic or linear chains and the interchain equilibration is also a facile process during polymerization. This intermolecular transetherification has been demonstrated by using low molecular weight aryl ethers to control the molecular weight of the polymer formed via ring-opening polymerization. © 1996 John Wiley & Sons, Inc.     

Electroinitiated polymerization of allylphenylether

Electroinitiated polymerization of allylphenylether via constant potential electrolysis was accomplished in acetonitrile at room temperature. Electroinitiated polymerization of the monomer yielded insoluble polymers on the surface of the anode together with soluble polymers in the bulk solution. The structural analyses of the polymers were done by ¹H-NMR and FTIR spectroscopy. ¹H-NMR results showed that monosubstituted aromatic ring of the monomer becomes tri-substituted during the electroinitiated polymerization. The effect of monomer concentration and applied potential on the rate of electroinitiated polymerization were also studied. © 1995 John Wiley & Sons, Inc.     

A convenient method for preparation of hydroxyl silicone oils with ring opening polymerization of octamethylcyclotetrasiloxane (D4)

Hydroxyl silicone can be prepared at a mild polymerization temperature with a moderately high yield via ring opening polymerization of D4 catalyzed by rare earth solid super acid SO₄^2?/TiO₂/Ln³⁺. The outstanding advantage of the method was that the viscosities of the products can be conveniently controlled by adjusting polymerization time, temperature, and the amount of water. The products were characterized by size-exclusion chromatography, ¹H-nuclear magnetic resonance, and Fourier transform-infrared spectroscopy. A cationic coordination-insertion polymerization mechanism was also proposed.     

Kinetic and particle size studies of emulsion polymerization of methyl methacrylate and styrene with using polyamidoamine dendrimer as seed

The emulsion polymerization of methyl methacrylate (MMA) and styrene (St) were investigated with using polyamidoamine (PAMAM) dendrimer as seed, potassium persulfate as initiator and sodium dodecyl sulfate as emulsifier. The effects of 4.0GPAMAM dendrimer concentration, initiator concentration, emulsifier concentration, monomer concentration, and polymerization temperature on the monomer conversion and polymerization rate were investigated. At the same time, the influence of the generation of PAMAM dendrimer on latex particle size was studied also. The results showed that the monomer conversion and polymerization rate increased with increasing initiator concentration, emulsifier concentration, monomer concentration, and polymerization temperature. But polymerization rate increased firstly with an increase in the 4.0GPAMAM dendrimer from 0.03 g to 0.09 g and then decreased with further increase to 0.12 g. When the concentration of 4.0GPAMAM dendrimer less than 1.449 × 10^?4 mol/L, the kinetic equation can be expressed by Rp∝[4.0GPAMAM]^0.772[SDS]^0.562[KPS]^0.589[M]^0.697, and the activation energy (Ea) of emulsion polymerization is 62.56kJ/mol. In additional, the copolymer latex particle size decreased and possessed monodispersity with increasing the generation of PAMAM dendrimer. According to FT-IR spectrum analysis, PAMAM dendrimer is successfully incorporated into the poly(PAMAM-St–MMA) latex particles.     

Kinetic study of γ-radiation-induced polymerization of ethylene in the presence of acetylene

The effects of acetylene on the γ-radiation-induced polymerization of ethylene were studied from the viewpoint of kinetics. The experiments were carried out under a pressure of 150–400 kg/cm²; the temperature was 30°C; the dose rates were 2.7 × 10⁴ and 1.1 × 10⁵ rad/hr; the acetylene content was 0–2.21%. Both the polymer yield and the molecular weight increased acceleratively with the reaction pressure in the polymerization containing 0.18% acetylene. The yield increased almost proportionally with the dose rate, and the molecular weight was found to be almost independent of the dose rate in the polymerization containing 2.21% acetylene. The polymerization rate and the molecular weight increased with reaction time, but the increment decreased with increasing acetylene content. The degree of increase in the molecular weight also decreased with increasing time. These results were analyzed by using a graphical evaluation method for kinetics, and the effects of acetylene on each elementary step in the polymerization discussed.     

茂－茚锆金属络合物催化乙烯/1－己烯共聚和丙稀均聚研究

Complexes （R^1Cp）（R^2Ind）ZrCl2, the catalysts previously reported active for ethylene polymerization showed high activity in ethylene/1-hexene copolymerization and propylene polymerization in the presence of MAO. The content of 1-hexene in copolymers ranged from 1.2% to 3.2%. In propylene polymerization the complex 1 showed the highest activity, up to 1.2×10^6 g of polypropylene per mol of catalyst per hour. Based on the analysis of NMR spectral data, the relationships between complex structures and polymerization results were explored.     

KINETICS OF SUSPENDED EMULSION POLYMERIZATION OF METHYL METHACRYLATE*

 The kinetics of suspended emulsion polymerization of methyl methacrylate (MMA), in which water acted as the dispersed phase and the mixture of MMA and cyclohexane as the continuous phase, was investigated. It showed that the initial polymerization rate (R_p0) and steady-state polymerization rate (R_p) were proportional to the mass ratio between water and oil phase, and increased as the polymerization temperature, the potassium persulphate concentration ([I]) and the Tween20 emulsifier concentration ([S]) increased. The relationships between the polymerization rate and [I] and [S] were obtained as follows: R_p0∝[I]^0.71[S]^0.23.The above exponents were close to those obtained from normal MMA emulsion polymerization. It also showed that the average molecular weight of the resulting poly(methylmethacrylate) decreased as the polymerization temperature,[I]and [S] increased. Thus, MMA suspended emulsion polymerization could be considered as a combination of many miniature emulsion polymerizations proceeding in water drops and obeyed the classical kinetics of MMA emulsion polymerization.     

Redox polymerization of acrylonitrile. Kinetics of the reaction initiated by the redox system tartaric acid–V5+

Kinetics of vinyl polymerization of acrylonitrile initiated by the redox system tartaric acid–V⁵⁺ have been investigated in aqueous sulfuric acid in the temperature range 30–40°C. The rates of polymerization and V⁵⁺ disappearance and the chain lengths of polyacrylonitrile were measured. From the results it is concluded that the polymerization reaction is initiated by an organic free radical arising from the V⁵⁺–tartaric acid reaction with termination by V⁵⁺ ions. A suitable kinetic scheme has been proposed, and the various rate and energy parameters were evaluated.     

Effects of ligands on the “living” radical polymerization initiated by the aged Cr2+ plus benzoyl peroxide system

The “living” radical polymerization of methyl methacrylate with the aged Cr²⁺ plus benzoyl peroxide (BPO) system in the presence of various amines as ligand has been studied in N,N′-dimethylformamide. Aliphatic amines such as ethylenediamine diminished the rate of polymerization, while dipyridyl (dipy) and o-phenanthroline (phen) accelerated the polymerization rate as follows: phen > dipy > pyridine ? none. Specifically, the rate of polymerization in the presence of phen had a maximum value at [phen]/[Cr²⁺] = 0.5. The retardation of polymerization by aliphatic amines was explained by the interaction of BPO with free and coordinated amines. The latter result may support the mechanism involving the complexed radical proposed for the living radical polymerization with the aged Cr²⁺ + BPO system. In the presence of phen the effects of aging period and aging temperature as well as polymerization temperature were studied and the nature of complexed radicals is discussed.     

Aqueous polymerization of acrylonitrile initiated by manganese(III) pyrophosphate-thiocyanate redox system: a kinetic study

Summary The kinetics of aqueous polymerization of acrylonitrile monomer (M) initiated by the Mn^III-KNCS redox system have been studied under deaerated conditions in the temperature range 26–40 °C at constant ionic strength. The overall rates of polymerization and the disappearance of Mn^III were determined. The polymerization was initiated by the free radicals arising from the Mn^III-thiocyanate redox reaction. The rate of polymerization was investigated at various concentrations of monomer and initiator. The effects of varying [Mn^III], [NCS^–], pH, total [P₂O _inf7 ^sup4– ], added [Mn^II], metal ions, ClO _inf4 ^sup– , Cl^– and SO _inf4 ^sup2– were examined. Dependence of the rate of polymerization on temperature was studied and activation parameters were computed from an Arrhenius plot. A suitable kinetic scheme consistent with the observed results is proposed and discussed.     

Radiation-Induced Polymerization of Acrylic Esters at High Pressure and Pressure-Volume Behavior of Polymer-Monomer Coexistence System as Polymerized

Pressure-volume (P-V) behavior and radiation-induced polymerization of methyl and n-butyl acrylic esters (MA and BA, respectively) were studied up to 7000 kg/cm² at 20°C. The P-V isotherms broke at 1900 and 1200 kg/cm² for MA and BA, respectively. The P-V isotherm for MA was not smooth in the pressure range between 3500 and 4000 kg/cm². The polymerization behavior varied with change in the P-V behavior; the polymerization rates were maximum at 1800 kg/cm for MA and 1000 kg/cm² for BA, and then minimum at 1900 kg/cm² for MA and 1100 kg/cm² for BA. The polymerization rates increased again above the pressures giving the minimum rates up to about 3000 kg/cm². Above 3000 kg/cm² the pressure dependence of the rates decreased up to 4000 and 4500 kg/cm² for MA and BA, respectively. Above these pressures, the pressure dependence of polymerization rates increased again. The P-V isotherms of as-polymerized polymer-monomer coexistence systems showed characteristic behavior near the polymerization pressure. From a comparison of these polymerizations and P-V behavior with those of methacrylic esters, we propose that acrylic esters align at high pressure and that freedom of rotation of ester group plays an important role in the mode of pressure-induced alignment of monomer molecules.