Effects of surfactants on acrylonitrile polymerization initiated by a Cr(VI)–cyclohexanone redox system: A kinetic study

The polymerization of acrylonitrile (AN) was kinetically studied with a Cr(VI)–cyclohexanone (CH) redox system as an initiator from 25 to 45° C in the presence of a surfactant. The rate of polymerization and the percentage of the monomer conversion increased as the concentration of the anionic surfactant [sodium dodecyl sulfate (SDS)] increased above its critical micelle concentration. However, the cationic surfactant (cetyltrimethylammonium bromide) reduced the rate considerably at higher concentrations, whereas the nonionic surfactant (TX‐100) had no effect on the rate. The effects of the Cr(VI), CH, AN, and H⁺ concentrations and the ionic strength on the rates were also examined. The presence of 0.015M SDS reduced the overall activation energy of the polymerization by 5.55 kcal/mol with respect to that in the absence of the surfactant. With increasing SDS concentration, the viscosity‐average molecular weight also increased. A suitable mechanistic scheme was proposed for the polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1147–1153, 2004     

高分子表面活性剂对细乳液聚合的影响

通过分析细乳液聚合过程中的单体乳液稳定性、聚合反应动力学以及聚合所得乳胶粒的特性,讨论了高分子表面活性剂对细乳液聚合的影响,并与普通低分子表面活性剂进行了比较。     

Cationic activated monomer polymerization of heterocyclic monomers

In the first part of this review the meaning of activation is discussed and selected examples of polymerizaton processes in which activation of monomer is required prior to actual propagation are presented. In some systems, activation of monomer proceeds with such a strong interaction between an activator and monomer that a new chemical entity is derived from the monomer. To describe the mechanism of such a process, the term ‘Activated Monomer Mechanism’ has been coined.

The main part of the review is concerned with cationic Activated Monomer (AM) polymerization of cyclic ethers. In this process, cyclic ether is activated by formation of protonated species in the presence of a protic acid. Reaction of the protonated (activated) cyclic ether with hydroxyl group containing compounds leads to ring opening reforming the hydroxyl group. Several repetitions of such a reaction constitute a chain process. Thus, in AM polymerization of cyclic ethers hydroxyl group containing compounds act as initiator, protic acid is a catalyst, growing chain end is fitted with hydroxyl group and the charged species is a protonated monomer. The important feature of such a polymerization mechanism is that due to the absence of charged species at the growing chain end, back-biting leading to the formation of macrocyclics can be eliminated.

The mechanism and kinetics of AM polymerization of cyclic ethers is discussed and the approach allowing one to determine the rate constant for propagation involving activated monomer species is outlined. The application of the AM concept to the copolymerization of cyclic ethers as well as to the polymerization of monomers containing both initiating (hydroxyl groups) and propagating (cyclic ether) functions within one molecule are presented.

In the subsequent parts of the review, examples of cationic AM polymerization of other types of heterocyclic monomers, including cyclic acetals, cyclic esters (lactones), amines and amides (lactams), are given.

Finally, the polyaddition of oxiranes to derivatives of phosphoric acid is discussed. Although this system does not conform to the AM polymerization scheme, it bears formal resemblance to earlier systems in such a sense that the activation of the cyclic ether is required for the reaction to occur.     

Polymerization of olefins and polar monomers catalyzed by bis(imino)Ni(II)/dibutylmagnesium/alkylaluminium halide systems

[Bis(N,N′‐dimesitylimino)acenaphthene]dibromonickel ( 1 ) when activated with diethylaluminium chloride (DEAC) is a very active catalyst for ethylene homopolymerization. The activity (A_E) of 1 /100 DEAC is twenty times greater than that of 1 /100 MAO and of the same order of magnitude as 1 /2000 MAO. In the case of homopolymerization of propylene the highest activity (A_P) was obtained at a ratio of 25/15 for Al_DEAC/Ni. Trialkylaluminium compounds were also found to act as cocatalysts for 1 . The PE synthesized with four different cocatalysts was found by ¹³C NMR to have dissimilar branching distributions. 1 /DEAC shows no activity for the polymerization of proximately substituted polar monomers. The introduction of dibutylmagnesium, (DBM) activates the 1 /DEAC system to copolymerize ethylene and a number of proximately substituted polar monomers. Compared with the 1 /MAO/monomer.AlR₃ catalyst system the former is three times more active for copolymerization of 5‐hexene‐1‐ol or 10‐undecen‐1‐oic acid with ethylene. The activity of copolymerization is 1 /24, 1 /5 and 1 /2 as active as homopolymerization, respectively, in the case of methyl vinyl ketone, vinyl acetate and ?‐caprolactam. In the case of tetrahydrofuran/ethylene, the 1 /MAO catalyst produced copolymers using AlR₃ pretreated THF whereas the 1 /DEAC/DBM catalyst produces homopolyethylene only. No polymerization occurred with an acrylonitrile/ethylene mixture in the presence of 1 /DBM/DEAC catalyst. © 2002 Society of Chemical Industry     

A critical evaluation of reaction calorimetry for the study of emulsion polymerization systems: thermodynamic and kinetic aspects

Protocols were examined for the measurement of rates and enthalpies of polymerization (ΔH_p) using reaction calorimetry. ΔH_p was determined to be 70.2 kJ mol⁻¹ for a series of seeded styrene emulsion polymerizations under typical emulsion conditions, in good agreement with literature values. However, there was a significant deviation from this value for small-particle systems, which is ascribed to surface effects, i.e. environmental effects on ΔH_p. Careful comparison between rate data obtained by calorimetry and by dilatometry leads to recommended procedures for obtaining reliable and accurate rate data using the former technique.     

Continuous dosing of fast initiator during vinyl chloride suspension polymerization: Polymerization rate and PVC properties

Continuous dosing of a fast initiator during the suspension polymerization of vinyl chloride has been carried out in a pilot‐scale reactor. The kinetics course of this polymerization and the particle features of the resulting grains were discussed and compared to the conventional polymerization with the same conversion and maximum reaction rate. It was found for the system used that a suitable dosage trajectory allows the reaction rate to remain constant during polymerization. This decreases the polymerization time up to 53% compared with the conventional suspension polymerization, while the molecular weight distribution and molecular weight of the final grains remained almost unchanged. SEM micrographs revealed that PVC grains prepared using this polymerization process had irregularly shaped, uneven particle surfaces and larger particle sizes. The grains also featured high porosity with loosely aggregated smaller primary particles that led to low levels of residual unreacted monomer. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44079.     

氯乙烯聚合研究进展

对近期氯乙烯聚合研究进展情况进行了综述,在聚合化学方面的研究包括复合引发剂引发氯乙烯聚合动力学、氯乙烯活性自由基聚合、茂金属催化聚合和阴离子聚合,在成粒机理方面的研究包括氯乙烯悬浮聚合和新型非均相聚合机理。     

The synthesis, spectroscopic and electrochemical properties, and application of new dyeing photoinitiator systems for acrylate monomers polymerization

New symmetrical bicationic polymethine dyes were synthesized and their spectroscopic and electrochemical properties were described. The bichromophoric dyes (benzothiazole, benzoxazole, indolinium derivatives) were investigated as sensitizers in the free radical photopolymerization initiated by their borate salts. The obtained kinetic results shown that bicationic polymethine dyes as the organoborate salts are much efficient photoinitiating systems of acrylate monomers polymerization than monocationic parent dyes. The rate of polymerization depends on ΔG_ET of electron transfer from borate anion to the excited singlet state of bicationic polymethine dye. The relationship between the rate of polymerization and the free energy of electron transfer process shows the dependence predicted by the classical theory of electron transfer.     

Mechanism and kinetics of emulsion copolymerization of vinylidene chloride—Critical conversion at the end of interval 2 and rate of polymerization

In this paper, the change of vapour pressure in the emulsion copolymerization of vinylidene chloride (VDC) was determined. It was observed that the vapour pressure drops at conversion about 60% when VDC/comonomer = 90/10 (wt). The types of emulsifier, concentrations of emulsifier and initiator, temperature do not effect these conversion values significantly. According to the principle of phase equilibrium, that the critical conversion at the end of Interval 2 in the emulsion copolymerization of VDC is about 60% was suggested. The effects of types of emulsifier, concentrations of emulsifier and initiator, temperature, types and concentrations of comonomer on rate of copolymerization were also studied. It was found that the different types of comonomer will have no great effect on the copolymerization rate and intrinsic viscosity of a VDC copolymer. And a common route and recipe can be adopted for producing different grades of PVDC latex.     

Novel functionalized monomers based on kojic acid: snythesis,characterization, polymerization and evalution of antimicrobial activity

Two novel acrylate monomers, [5-(benzyloxy)-4-oxo-4H-pyran-2-yl]methyl acrylate and {1-[(5-(benzyloxy)-4-oxo-4H-pyran-2-yl)methyl]-1,2,3-triazol-4-yl}methyl acrylate were synthesized by the reaction of 5-benzyloxy-2-(hydroxymethyl)-4H-pyran-4-one and 5-(benzyloxy)-2-{[4-(hydroxymethyl)-1,2,3-triazol-1-yl]methyl}-4H-pyran-4-one with acryloyl chloride in the presence of triethylamine, respectively. These monomers were polymerized using 2,2^′-azobisisobutyronitrile (AIBN) as the initiator in N,N-dimethylformamide:14-dioxane (10:1) solution. The thermal behavior of the polymers was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized compounds were evaluated for their antibacterial and antifungal activites aganist bacteria and fungi using the disk diffusion method. The results indicated that some of these compounds demonstrated moderate to good antibacterial and antifungal activities.     

Dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate: Synthesis and characterization

Dispersion polymerization of acrylamide (PAM) has been successfully carried out in aqueous ammonium sulfate media by using poly(acryloyloxyethyl trimethylammonium chloride) (PAOTAC) as the polymeric stabilizer and 2,2′‐azobis(2‐methyl propionamidine) dihydrochloride (AIBA) as the initiator. The polymerization behaviors with varying concentrations of acrylamide, PAOTAC, AIBA, and ammonium sulfate were investigated. The reaction conditions for stable dispersion were concentrations of 5–10% for acrylamide, 0.6–1.8% for the stabilizer, 0.92–1.84 × 10^?4 mol/L for the initiator, and 24–30% for the salt. The resulting conversion–time curves were S‐shaped, as is typically observed in polymerization. Polydisperse spherical particles were formed in the system. An image analyzer photographed the size of the dispersed particles and their distribution was measured. The mechanism and kinetics for the dispersion polymerization were discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1397–1405, 2002     

The spontaneous polymerization of methyl methacrylate: 6. Polymerization in solution: participation of transfer agents in the initiation reaction

The rate of the spontaneous polymerization of methyl methacrylate is strongly affected by the addition of transfer agents. The kinetics are interpreted in terms of a participation of transfer agents in the initiation step. In this, the original biradical, .M₂., which is produced from two monomer molecules and which has a high self-termination probability, is converted into polymerizable monoradicals. Increase in the concentration of a strong transfer agent leads to double-transferred compound HH1, the mass spectral identification of which is to be regarded as first direct evidence for the existence of biradical .M₂..     

氯乙烯聚合用引发剂的研究

在研究单一引发剂分解动力学的基础上,提出复合引发剂分解动力学模型,并结合ＶＣＭ聚合动力学,为恒速聚合的复合引发体系的配方设计提供指导。     

Preparation and characterization of maleic anhydride-grafted desulfurization rubber powder by free-radical polymerization

The objective of the article was to enhance the recycling value of solid waste rubber by surface functionalization of desulfurized rubber powder using a one-pot method based on free-radical polymerization theory. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscopy, and elemental analysis were used to characterize the maleic anhydride-grafted desulfurized rubber powder, and the grafting mechanism was also investigated. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that maleic anhydride was grafted onto the desulfurized rubber powder. Thermogravimetric analysis indicated that the maleic anhydride-grafted desulfurized rubber powder and desulfurized rubber powder possessed different thermal properties and structure. The results of scanning electron microscopy and elemental analysis illustrated that the surface of the desulfurized rubber powder was covered with a layer of fold-like maleic anhydride polymer. The mechanism of grafting desulfurized rubber powder with maleic anhydride may be achieved by replacing the active α-H on the methylene group of the desulfurized rubber macromolecule chain.     

Vinyl polymerization: 414. Polymerization of vinyl monomer initiated by poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride

The polymerization of vinyl monomer initiated by an aqueous solution of poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride (poly(Q-DMAEM-CI) has been carried out at 85°C. The effects of the amounts of vinyl monomer, poly(Q-DMAEM-CI) and water on the conversion of vinyl monomer have been studied. The overall activation energy in the polymerization of MMA is estimated as 41.9 kJ mol^?1. The polymerization proceeds through a radical mechanism. The location in which the polymerization occurs is discussed. The selectivity for vinyl monomer is explained by ‘the concept of hard and soft hydrophobic areas and monomers’.     

Room temperature living cationic polymerization of styrene with HX-styrenic monomer adduct/FeCl3 systems in the presence of tetrabutylammonium halide and tetraalkylphosphonium bromide salts

Living cationic polymerization of styrene was achieved with a series of initiating systems consisting of a HX-styrenic monomer adduct (X = Br, Cl) and ferric chloride (FeCl₃) in conjunction with added salts such as tetrabutylammonium halides (nBu₄N⁺Y⁻; Y⁻ = Br⁻, Cl⁻, I⁻) or tetraalkylphosphonium bromides [nR′₄PBr; R′ = CH₃CH₂-, CH₃(CH₂)₂CH₂-, CH₃(CH₂)₆CH₂-] or tetraphenylphosphonium bromide [(C₆H₅)₄PBr] in dichloromethane (CH₂Cl₂) and in toluene. Comparison of the molecular weight distributions (MWDs) of the polystyrenes prepared at different temperatures (e.g., −25 °C, 0 °C and 25 °C) showed that the polymerization is better controlled at ambient temperature (25 °C). The polymerization was almost instantaneous (completed within 1 min) and quantitative (yield ∼100%) in CH₂Cl₂. In CH₂Cl₂, polystyrenes with moderately narrow (M_w/M_n ∼ 1.33-1.40) and broad (M_w/M_n ∼ 1.5-2.4) MWDs were obtained respectively with and without nBu₄N⁺Y⁻. However, in toluene, the MWDs of the polystyrenes obtained respectively with and without nBu₄N⁺Y⁻/nR′₄P⁺Br⁻ were moderately narrow (M_w/M_n = 1.33-1.5) and extremely narrow (M_w/M_n = 1.05-1.17). Livingness of this polymerization in CH₂Cl₂ was confirmed via monomer-addition experiment as well as from the study of molecular weights of obtained polystyrenes prepared simply by varying monomer to initiator ratio. A possible mechanistic pathway for this polymerization was suggested based on the results of the ¹H NMR spectroscopic analysis of the model reactions as well as the end group analysis of the obtained polymer.     

Mechanistic study of the formation of amphiphilic core-shell particles by grafting methyl methacrylate from polyethylenimine through emulsion polymerization

The mechanism for the formation of amphiphilic core-shell particles in water is elucidated via a kinetic study of semi-batch polymerization of methyl methacrylate (MMA) grafted from polyethylenimine (PEI) initiated with tert-butyl hydroperoxide in an emulsion polymerization. The monomer conversion, the polymerization kinetics, the particle size, the particle number density, the poly(methyl methacrylate) (PMMA) core diameter, the percentage of unbound PEI, and the grafting efficiency of PMMA were determined at various times during the polymerization. The particle number density and the percentage of unbound PEI were almost independent of the controllable variables. The particle sizes and the core diameters increased with each consecutive batch of monomer addition, while the grafting efficiency of PMMA decreased. These data supported the hypothesis that the PEI-g-PMMA graft copolymers were formed early in the polymerization and later self-assembled to a new phase, micellar microdomains. These microdomains act as loci for subsequent MMA polymerization as the monomer is fed into the reaction, without subsequent formation of new particles. The size of the resulting highly uniform core-shell particles (99-147 nm) can be controlled by choosing the amount of monomer charged. Thus, this polymerization method is viable for a large scale production of core-shell particles with high solids content.     

Chloro-Nickel and Chloro-Cobalt Complexes Containing Phosphine Ligands: Efficient Initiators for Polymerization of Alkynes

We have developed a new series of single-component air- and moisture-stable catalysts for alkyne polymerization based on chloro-nickel and chloro-cobalt complexes containing phosphine ligands. The polymerization of p-diethynylbenzene initiated by these complexes proceeds smoothly in the presence of amines at room temperature to afford soluble -conjugated polymers in yields as high as 81% with weight-average molecular weight up to 17 600.     

无皂乳液聚合理论及动力学模型

介绍了无皂乳液聚合理论和相关的动力学模型，并进行了简要评述和展望。     

Anionic polymerization of secondary aminostyrene and characterization of the polymer

Preparation by anionic living technique and characterization of poly(secondary aminostyrene) having narrow molecular weight distribution were investigated. N‐isopropyl‐N‐trimethylsilyl‐4‐vinylbenzylamine (SBA) was purified by use of sec‐butylmagnesium bromide as a purging reagent under high vacuum. SBA was anionically polymerized with n‐butyllithium or cumylpotassium in tetrahydrofuran at −78°C under high vacuum to yield the corresponding polymer (PSBA) in 100% yield. Subsequent deprotection of the trimethylsilyl group from PSBA produced poly(N‐isopropyl‐4‐vinylbenzylamine) (PBA) of the desired molecular weights (M_n: 1.3 × 10⁴–17 × 10⁴, determined by membrane osmometry) with narrow molecular weight distribution (M_w/M_n: 1.07–1.03, determined by gel permeation chromatography). The living lithium carbanion of PSBA can initiate styrene (St) to yield PSBA‐b‐PSt block copolymer (M_n = 4.0 × 10⁴, M_w/M_n = 1.05), and the polystyryllithium can initiate SBA to yield PSt‐b‐PSBA (M_n = 3.7 × 10⁴, M_w/M_n = 1.25). The deprotection of the trimethylsilyl group from the two block copolymers produced new block copolymers containing poly(secondary aminostyrene) block. Anionic reactivity of SBA and basic properties of PSBA are discussed in terms of the ¹³C chemical shift of β‐carbon in the vinyl group of SBA and steric effect. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2039–2048, 1999