Emulsion polymerization of vinyl acetate initiated by intermittent γ radiation

The reaction kinetics of emulsion polymerization of vinyl acetate (VAc) monomer have been studied by using intermittent γ radiation. The purpose of this technique is to take advantage of the poly merization reaction which still continues after the radiation production has been stopped, as expected by the Smith–Ewart rate theory. Tween 20 (polyoxyethylene sorbitan monolaurate), was used as the emulsifier. The polymer conversion was determined by using the dilatometric method. The polymerization rate R_p decreased with increase in emulsifier content. The Smith–Ewart rate theory cannot explain the experimental evidence satisfactorily. The average polymerization rate R_p between 20% and 80% conversion is a function of irradiation dose rate and can be written where a₁ and a₂ is a constant in which the value depends on the emulsifier content in the emulsion and I is the irradiation dose rate.     

Graft polymerization of acrylic acid onto starch using potassium permanganate acid (redox system)

Graft polymerization of acrylic acid (AA) onto rice starch using postassium permanganate/acid redox system as initiator was investigated. When starch was reacted with KMnO₄ solution, MnO₂ was deposited onto starch. The dependence of MnO₂ amount deposited was directly related to KMnO₄ concentration. Subjecting the MnO₂-containing starch to a solution consisting of monomer (AA) and acid (citric, tartaric, oxalic and hydrochloric acid) formed poly(AA)–starch graft copolymers. The graft yield, expressed as meq COOH/100 g starch, was measured by the amount of MnO₂ deposited, AA concentration, material-to-liquor ratio, kind and concentration of acid, as well as temperature and duration. Finally, the newly prepared poly(AA)–starch graft copolymers were applied to cotton textiles to determine their suitability as sizing agents. The highest graft yield was obtained with citric acid and the least with hydrochloric acid, with tartaric and oxalic acid in between. The graft yield increased by increasing the concentration of acid to a certain concentration beyond which grafting leveled off. A similar trend was observed when the magnitude of grafting was related to the amount of MnO₂ deposited. The graft yield increased by increasing the polymerization temperature from 30° to 50°C. Increasing the temperature to 60°C is accompanied by decreased grafting. On the other hand, fabric samples sized with poly(AA)–starch graft copolymers acquire higher tensile strength, elongation at break, and abrasion resistance than that sized with native rice starch, i.e., poly(AA)–starch graft copolymers serve as good sizing agents for cotton textiles. A tentative mechanism for grafting rice starch with AA using the KMnO₄/acid redox system was elucidated. © 1995 John Wiley & Sons, Inc.     

Microemulsion polymerization of butyl acrylate initiated by γ rays

Radiation polymerization of butyl acrylate was carried out in a microemulsion stabilized with sodium 12-butinoyloxy-9-octadecenate (SBOA). The stable and reddish latex with high polymer content and low emulsifier content was successfully produced in this way. It was found that, for most cases, the polymerization rate shows three intervals: the increasing period, the plateau period, and the decreasing period. The length of the nucleation period becomes longer at a higher dose rate (D) and lower emulsifier content (E). The plateau region of polymerization rate is lengthened with the increase of monomer and emulsifier content and shortened with the increase of dose rate. It was shown that monomer content, emulsifier content, and dose rate have great effects on R_p (the polymerization rate in the plateau region, or the maximum polymerization rate during polymerization) and M_n (the molecular weight of the polymer). R_p ∞ [M^0.93D^1.27[E]^−1.07; M_n ∞ [M]^0.65D^0.28[E]^−1.66. The polymerization mechanism is discussed based on these results. © 1996 John Wiley & Sons, Inc.     

Radical polymerization of acrylonitrile initiated by α-picolinium p-chlorophenacylid

The radical polymerization of acrylonitrile (AN) with α-picolinium p-chlorophenacylid (α-PCPY) as initiator using carbon tetrachloride as inert solvent was investigated at 50°C. The polymerization follows ideal kinetics: the exponent values calculated for the initiator and monomer were found to be 0.5 and unity, respectively. A free radical mechanism with bimolecular termination was confirmed by the inhibiting effect of hydroquinone, a radical quencher. The rate of polymerization was a direct function of initiator (α-PCPY) concentraction, monomer (AN) concentration and temperature. The overall activation energy calculated was 56 kJ/mol. The polymerization was favoured by polar solvents and retarded by non-polar solvents.     

Electro‐induced polymerization of acrylamide initiated by the potassium permanganate–titriplex VI redox system

The polymerization of acrylamide (AAm) was carried out with a potassium permanganate–Titriplex VI redox initiator system with and without electrolysis. Because of the high metal‐ion concentration in general, low‐molecular‐weight polymers were obtained (weight‐average molecular weight = 2600–4000). The effect of potassium permanganate and AAm concentrations and temperature on the polymerization yield was studied and compared with results obtained under the same experimental conditions used for electrolysis. The results of Fourier transform infrared spectroscopy, atomic absorption spectrometry, and scanning electron microscopy (SEM) results are given. SEM micrographs of the polymer obtained by electrochemical methods exhibited smoother surfaces than those obtained by nonelectrolytic methods. In the absence of potassium permanganate, there was no polymerization under experimental conditions. A possible reaction mechanism is suggested. The electro‐induced system resulted in about a 50% increase in the yield. Manganese content in the electro‐induced and chemical polymerization systems were 2.7 and 8.2%, respectively, supporting the yield increase in the electro‐induced system. A graphite electrode was used and resulted in a high yield and a fibrous polymeric structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1526–1534, 2001     

Ring-opening polymerization of ε-caprolactone initiated by cyclopentadienyl sodium

Polymerization of ε-caprolactone had been investigated with cyclopentadienyl sodium as an initiator. The effects of reaction time, temperature, and concentration of the initiator on the yield and molecular weight of the polymer were discussed. It was shown that the high molecular weight of poly(ε-caprolactone) (13 × 10⁴) was obtained with cyclopentadienyl sodium initiator, and the mechanism of polymerization was also discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1273–1276, 1998     

氧化还原体系引发苯乙烯乳液聚合

以不同的过氧化物引发剂分别与硫酸亚铁组成氧化还原引发体系,引发苯乙烯的乳液聚合,研究反应温度和还原剂用量等对聚合的影响.采用气相色谱、三检测体积排除色谱、动态光散射对单体转化率、聚苯乙烯的相对分子质量及其分布和乳胶粒径进行了分析.结果表明:升高温度或增加还原剂用量均会使聚合物的相对分子质量增大,聚合反应速率加快,与常规...     

Microemulsion polymerization of methyl methacrylate initiated with γ ray

Polymerization of methyl methacrylate was studied in an oil and water microemulsion stabilized with styrene 12-butinoyloxy-9-octadecenoic acid. During the polymerization the size change of the monomer-swollen particles with conversion was measured with photon correlation spectroscopy, and the hydrodynamic diameter of the final polymer latex was about 50 nm. The polymerization kinetics in this microemulsion were also investigated. The apparent plateau of the polymerization rate was observed at a low dose rate and high emulsifier content. The mechanism leading to this plateau was discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2621–2626, 1999     

Behaviour of poly(β-hydroxybutyric acid) in dilute solution

The refractive indices of poly(β-hydroxybutyric acid) (PHB) at four wavelengths have been determined via different procedures. Viscometric and light scattering measurements have been made on solutions of eight samples of PHB (M_w = 20·9 × 10³?929 × 10³ g mol^?1) in 2,2,2-trifluoroethanol. From the dependences of intrinsic viscosity and of radius of gyration on molar mass, the conformation of PHB in dilute solution is shown to be that of a random coil. The findings are discussed in relation to existing conflicting evidence on the conformation of this polymer.     

Electrochemical polymerization of β‐naphthalene sulfonic acid

β‐Naphthalene sulfonic acid (β‐NSA) has been electrochemically polymerized in a mixed electrolyte of boron trifluoride diethyl etherate (BFEE) solution mixed with a certain amount of trifluoroacetic acid (TFA) or concentrated sulfuric acid (SA). The poly(β‐naphthalene sulfonic acid) (PNSA) film prepared from the medium of BFEE+TFA was partly soluble in methanol. On the other hand, the polymer obtained from the system of BFEE+SA was soluble in water and general polar organic solvents such as methanol, alcohol, and acetone. The structure of PNSA was examined by infrared and UV spectra. Fluorescent spectral studies indicate that the polymer is a blue light emitter with fluorescence quantum efficiency of ～ 4%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1939–1944, 2004     

Redox polymerization: Kinetics of polymerization of acrylonitrile initiated by the system 2,2′-thiodiethanol/trichloroaquobipyridylmanganese(III) in dilute sulfuric acid

The kinetics of polymerization of acrylonitrile and methyl methacrylate initiated by the redox system 2,2′-thiodiethanol/trichloroaquobipyridylmanganese(III) have been investigated in the temperature range 20–35°C in dilute sulfuric acid. The oxidation of the substrate in the absence of monomer has also been studied. A third-order reaction involving the complex, the substrate, and H⁺ leads to the production of primary radicals which initiate polymerization of the monomers. The primary radicals are more reactive towards methyl methacrylate than towards acrylonitrile. The termination of polymerization with both monomers is by mutual interaction between the growing radicals. A suitable kinetic scheme has been proposed, and the rate constants evaluated.     

Kinetic studies of aqueous polymerization of acrylic acid initiated using potassium bromate/sodium metabisulphite redox pair

Aqueous polymerization of acrylic acid was conducted using potassium bromate/sodium metabisulphite redox initiators under isothermal conditions. The initial polymerization rates were determined with variation in temperature and in the initial concentrations of acrylic acid, potassium bromate and sodium metabisulphite. The effect of pH on polymerization was also investigated. An overall activation energy of 28·62kJmol^-1 was obtained over the temperature range 13–43°C. The polymerization is initiated by free radicals and terminated by a combination of monomolecular and bimolecular modes. The cage effect and chain transfer to bisulphite anion are probably both significant. © 1998 SCI.     

Aqueous polymerization of acrylamide initiated by Ce(IV)-thiomalic acid redox system

Summary The use of a Ce (IV)-thiomalic acid (Ce⁴⁺-TMA) redox system as an initiator in the polymerization of acrylamide (M) in an aqueous medium has been investigated. The Ce⁴⁺ forms a 11 complex with TMA, decomposing through free radical mechanism in an acid medium. From 5 to 15% conversion the rate equation is where Rp is the rate of polymerization and x is 0.5 or 1.0 depending upon the concentration of monomer. The overall energy of activation has been calculated to be 9.12 k cal. deg^–1 mol^–1(38.12 kJ/mol) in the investigated range of temperature (25°–40°C) the degree of polymerization (P) of the polymer is directly proportional to [M]. The number of average molecular weight of the polymer remains unaffected at lower concentration of Ce⁴⁺ and is found to decrease at higher concentrations.In this investigation the kinetics and mechanism of the Ce(IV)-thiomalic acid (TMA) redox system to initiate the polymerization of acrylamide has been studied.Acrylamide (E. Merck) was purified by usual methods. Thiomalic acid and eerie ammonium sulfate were used without purification. All solutions were p repared in twice distilled water.The polymerization procedure adopted was similar to the one used by MISRA et al. [3, 4]. The polymerization was followed by quantitative estimation of the double bonds in acrylamide as described [8]. A small variable induction period was observed perhaps due tothe residual oxygen in the thiol solution. Curves were plotted after eliminating the induction period.The average molecular weights of the p olymers were determined by viscosity measurements at 30°C in an aqueous medium using the relationship of DAINTON et al. [2]. Where []=intrinsic viscosity of the polymer solution and ¯Mn=molecular weight of the sample.     

Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane initiated by potassium isopropoxide

Kinetics of the anionic ring‐opening polymerization of octamethylcyclotetrasiloxane (D₄) in bulk initiated by potassium isopropoxide was studied. Several promoters including N‐methyl‐2‐pyrrolidinone (NMP), N,N‐dimethylformamide (DMF), and diglyme were used. It is indicated that the reactions are first‐order in D₄ during the initial stage of polymerization. The polymerization rate of D₄ is influenced by a number of factors, such as the nature of promoters, the molar ratio of promoter to initiator (C_p/C_i ratio), and the reaction temperatures. With the use of NMP as promoter, the polymerization rate constant at 30°C is 10.482 h^?1 with the C_p/C_i ratio equal to 3.0. As the C_p/C_i ratio increases, the polymerization rate constant increases sharply and the cyclic oligomers content in polymer decreases evidently. The back‐biting reaction that leads to the formation of decamethylcyclopentasiloxane (D₅) occurred in the polymerization of D₄. The rate of the D₅ formation relatively to the rate of D₄ conversion increases with the conversion of D₄. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3510–3516, 2006     

Acrylonitrile polymerization initiated by Ce(IV)–cyclohexanone redox system in presence of surfactant

The rate of polymerization of acrylonitrile, using the Ce(IV)–cyclohexanone redox system as an initiator, was studied kinetically, in the presence of 0.015M sodium dodecyl sulfate (SDS), over a temperature range of 25–45°C. The rate of polymerization (R_P), percentage of monomer conversion, and rate of Ce(IV) consumption (?R_Ce) were found to increase with the concentration of SDS, above its CMC. The effect of [AN], [Ce(IV)], [H⁺], and the ionic strength were also studied. The overall activation energies for the polymerization processes were computed to be 23.14 and 17.64 kcal/mol in the absence and presence of 0.015M SDS. A suitable kinetic mechanistic scheme for the free‐radical mechanism was proposed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2066–2072, 2003     

Potassium persulphate-malonic acid redox pair initiated polymerization of methacrylamide

Summary The kinetics of aqueous polymerization of methacrylamide initiated by potassium persulphate-malonic acid redox pair has been investigated at 50±1°C under nitrogen atmosphere. The initial rate of polymerization has been found to be square root dependence to the initial concentration of potassium persulphate and malonic acid. The order of reaction with respect to monomer has been found to be unity. The overall energy of activation has been found to be 66±1 KJ/mol. The effect of addition of manganous sulphate and sulphuric acid has been investigated. On the basis of experimental results a suitable mechanism has been proposed.     

Concentrated emulsion polymerization of methyl methacrylate/butyl acrylate initiated by a redox system

Stable concentrated emulsions of methyl methacrylate/butyl acrylate were prepared with sodium dodecyl sulfate and cetyl alcohol as the compound surfactant and poly(vinyl alcohol) as the major reinforcer of the liquid film. With a redox system based on benzoyl peroxide/N,N′‐dimethyl phenylamine introduced into the concentrated emulsions, polymer particles with different shapes and sizes were obtained by initiation of the polymerization at low temperatures. We investigated the kinetic behaviors of concentrated emulsion polymerization and drew linear regression diagrams of its time–conversion curves in a constant rate phase (conversions ranged from 20 to 70%), and the experimental results show that the variation of the concentrations of the compound surfactant and initiator, the categories of reinforcers of the liquid film, the temperatures, and so on were responsible for the polymerization stability and the polymerization rate. Finally, the kinetics equation and activation energy of the initiator were obtained. The particle size and distribution of particle diameters of latex particles were determined by photon correlation spectroscopy. The determination results reveal that concentrations of the compound surfactant, polymerization temperatures, and so on affected the shape and size of the polymer particles greatly. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1695–1701, 2005     

Stereoelective polymerization of β-butyrolactone

Racemic β-butyrolactone was polymerized using chiral initiators obtained from the reaction of organometallic derivatives (ZnEt₂, CdMe₂, AlEt₃) with R(−) 3,3 dimethyl-1,2 butanediol. With the zinc initiator, R(+) enantiomer is preferentially incorporated in the polymer chain with a stereoelectivity ratio r_R equal to 1.6. Crude polymer was fractionated into a crystalline, predominantly isotactic, part and an amorphous heterotactic part, both optically active. Sites of different stereospecificities, present in the initiator, are all active for the stereoelective polymerization. With the cadmium initiator, S(−) enantiomer is preferentially polymerized (r_s = 1.01), extending homosteric-antisteric rules previously established for thiiranes. Aluminium initiator leads to an homosteric process (r_R = 1.1). Chiroptical properties (o.r.d. and c.d.) of polymers prepared with zinc initiator show a predominance of R-configurational units, indicating that ring-opening occurs by O-acyl cleavage with retention of configuration.     

Polymer/metal interpenetrating phase composites prepared via γ‐ray initiated in‐situ emulsion polymerization

The poly(methylmethacrylate)/metal and poly(butylacrylate‐co‐styrene)/metal interpenetrating phase composites (IPCs) were prepared via γ‐ray irradiation in‐situ bulk and emulsion polymerization, respectively. The monomers were first introduced into open‐cell aluminum foam and aluminum alloy foam and were in‐situ polymerized by γ‐ray irradiation at room temperature. The characterization and compressive test results showed that this method expands the variety of the polymer component resulting in a useful range of physical properties of the IPCs, such as density and porosity. The PMMA/metal IPC has a high polymer filling ratio, modulus and exhibits a similar compressive behavior to that of PMMA. On the other hand, the P(BA‐co‐St)/metal IPC has a relatively low polymer filling ratio and its compressive behavior is similar to that of metal foam matrix, but it has wider plastic plateau than the component metal foams, like the case of metal foam filled with rubber. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Radical polymerization of acrylamide initiated by ceric ammonium nitrate-methionine redox initiator system

The polymerization of acrylamide, initiated by a cerium (IV) [Ce(IV)] ammonium nitrate-methionine redox initiator system, was carried out in an aqueous solution at different reaction conditions. The dependence of molecular weight and polymerization yield on the concentration of Ce(IV), polymerization time, and temperature was determined. The molecular weight distributions (MWD) of the resulting polymers were examined using the HPLC method. Based on the HPLC results, optimum reaction conditions were determined that provided an opportunity to obtain a polymer that had a narrow MWD. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1643–1648, 1997