水性苯乙烯-丙烯酸-马来酸酐共聚物的合成及表征

以过氧化苯甲酰为引发剂、二丙二醇二甲醚为溶剂,采用自由基聚合方法,合成苯乙烯-丙烯酸-马来酸酐三元共聚物。考察单体配比、引发剂用量、反应温度对聚合物性能的影响,并用红外光谱、凝胶色谱、差示扫描量热法等对共聚物进行表征。结果表明,最佳工艺条件是:n(ST):n(AA):n(MA)=6:3:1,反应温度为85℃,引发剂为单体质量的12%;得到数均分子量为4678、分子量多分散指数为1.45的三元共聚物。     

DFT study on pathways of partial oxidation of DME under cold plasma conditions

Pathways of partial oxidation of dimethyl ether under cold plasma conditions have been studied by density functional theory method in this work. Total energies, energy barriers and reaction enthalpies at 0 K or 298.15 K have been calculated at GGA/PW91/DNP level. The calculation shows that, with the presence of O₂, the energy barrier of dimethyl ether conversion is reduced and the conversion from dimethyl ether to H₂ and CO is promoted under cold plasma conditions. The formation of syngas is through a multi-step pathway via the conversions of methoxymethyl radical (CH₃OCH₂·), formaldehyde, HCO·, CH₃·, CH₃O·, while the recombination of H generates extra hydrogen. The formation and effect of dimethyl ether anions have been also investigated in this work.     

Polymérisation des méthacrylates d'ethers glycériques par le peroxyde de benzoyle: Accélération de la polymérisation par les sulfinates d'amines tertiaries

The kinetic study of the radical polymerization of phenyl glyceric ether methacrylate, taken as model of the corresponding derivative of bisphenol A, initiated by the system benzoyl peroxide/dimethyl p-toluidine p-toluene sulfinic acid salt, was performed. The effect of hydroxylic groups of the monomer on the polymerizability was established. The system used as initiator allows rapid polymerization of the monomer in presence of stabilizers.     

Novel addition-fragmentation agent in cationic photopolymerization

The aim of present study is to examine the photo-initiation efficiency of N,N-dimethylacrylamide-based allylic ammonium salt as one component addition-fragmentation agent (cationic photoinitiator cum radical source) in free radical accelerated cationic polymerization. Novel addition-fragmentation agent (AFA), 2-(N,N-dimethylcarboxy-3-propenyl)(phenylcarbonyl-4-phenylene) dimethyl ammonium hexafluoroantimonate (DMPDA) was synthesized as cationic photoinitiator and its initiation efficiency was examined in polymerization of cyclohexene oxide (CHO), isobutyl vinyl ether (IBVE), and n-butyl vinyl ether (n-BVE) in CH₂Cl₂ solvent at wavelength λ > 290 nm. The rate of polymerization increases with the increase in initiator concentration and reaction time. The results demonstrate that DMPDA acts as an efficient photoinitiator (AFA) without use of radical source in free radical accelerated cationic polymerization.     

Preparation of polymeric microcapsules enclosing microbial cells by radical suspension polymerization via water-in-oil-in-water emulsion

Polymeric microcapsules enclosing Saccharomyces cerevisiae were prepared by radical suspension polymerization via water-in-oil-in-water emulsion. Trimethylolpropane trimethacrylate and 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) were used as monomer and radical initiator, respectively. A culture medium with suspended yeast cells, monomer solution with the dissolved radical initiator, and poly(vinyl alcohol) aqueous solution were used as inner aqueous phase, oil phase, and outer aqueous phase, respectively. The influence of microcapsule preparation parameters on the viability of encapsulated cells and encapsulation efficiency was investigated. The radical polymerization process did not cause significant damage to encapsulated yeast cells. Decreased weight ratio of aqueous phase to oil phase resulted in increased encapsulation efficiency of the cells. The diameter of the microcapsules could be controlled by varying the agitation rate.     

A radical scavenging reaction of α-tocopherol with methyl radical

To study a radical scavenging reaction of α-tocopherol, it was reacted with methyl radical in dimethyl sulfoxide. Two main products, a geminal dimethyl cyclohexadienone and methyl ether of α-tocopherol, were obtained and these structures were determined by¹³C nuclear magnetic resonance spectroscopy. The radical methylation data of α-tocopherol suggested that a delocalized radical species would be an intermediate. TMIG-RI No. 3.     

新型自由基引发剂偶氮二异丁酸二甲酯的合成及其在聚合物多元醇生产中的应用

详细介绍了新型自由基引发剂偶氮二异丁酸二甲酯（AIBME）的性质和合成工艺,同时介绍了AIBME在聚合物多元醇生产中的应用情况,并将其与传统的自由基引发剂偶氮二异丁腈（AIBN）进行了对比。使用AIBME作引发剂可提高乙烯基单体的转化率,很好地控制聚合反应速率和产品的黏度,防止产物结块。由于AIBME分子中不含有毒的-CN基网,符合环保要求,还可拓展下游产品的应用范围。     

Dispersion polymerization of NVCA in compressed liquid dimethyl ether in the presence of PDMS-g-pyrrolidone carboxylic acid: Effects of initiators

Dispersion polymerization of N-vinylcarbazole (NVCA) was performed in compressed liquid dimethyl ether with PDMS-g-pyrrolidonecarboxylic acid (Monasil PCA™) as the surfactant and with 2,2′-azobis(2,4-Dimethylvaleronitrile) (V-65), 2,2-azobisisobutyronitrile (V-60) (AIBN) and dimethyl 2,2′-Azobis(isobutyrate) (V-601) as the initiators. The effects of polymerization temperature, initiator types and initiator concentration were investigated. Spherical poly(N-vinylcarbazole) (PVK) particles were produced, even at 40 °C, by the low-temperature initiator, 2,2′-azobis(2,4-Dimethylvaleronitrile) (V-65). Through low-temperature polymerization with V-65, we successfully obtained high molecular weight PVK.     

Volume‐expandable monomer 5,5‐dimethyl‐1,3‐dioxolan‐2‐one: Its copolymerization behavior with epoxide and its applications to shrinkage‐controlled epoxy‐curing systems

The copolymerization of epoxides and a six‐membered cyclic carbonate, 5,5‐dimethyl‐1,3‐dioxan‐2‐one (DM6CC), was carried out with 1,8‐diazabicyclo[5.4.0]undec‐7‐ene as an initiator. In the copolymerization of glycidyl phenyl ether (GPE) and DM6CC, DM6CC remarkably accelerated the polymerization rate of GPE and also effectively suppressed chain‐transfer reactions, which occur in the homopolymerization of the epoxide. This suppression resulted in the formation of the corresponding copolymer with a higher molecular weight. Similar effects of DM6CC were also observed in a curing system with a Novolac‐type multifunctional epoxide (Novolac glycidyl ether). The curing reaction of the epoxide in the presence of DM6CC smoothly proceeded and yielded the corresponding networked polymer, showing a decrease in the volume shrinkage as the DM6CC content increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 372–378, 2005     

Synthesis and photo‐curing behaviors of silicon‐containing (vinyl ether)–(allyl ether) hybrid monomers

A series of silicon‐containing (vinyl ether)–(allyl ether) hybrid monomers used in nano‐imprint lithography resists were synthesized and subjected to photo‐initiated polymerization. The surface energies of the monomers and the resulting polymer films were then investigated. The surface energies of the monomers were very low at less than 15 mJ m^–2. The photo‐curing behaviors of the five hybrid monomers were investigated using real‐time Fourier transform infrared spectroscopy. The monomers were sequentially initiated with cationic (PAG201) and mixed (cationic initiator PAG201, radical initiator ITX or TPO) initiators. The vinyl ether double bond polymerized both rapidly and completely, whereas the allyl ether double bond remained when PAG201 was used as the photo‐initiator and polymerized completely with mixed initiators. The different double bonds of the silicon‐containing (vinyl ether)–(allyl ether) hybrid monomer increased the efficiency of the polymerization and overcame the intrinsic limitations of the free radical and cationic polymerization processes, including strong oxygen inhibition, large volume shrinkage and high humidity sensitivity. The five monomers with low viscosity, low surface energy, good thermal stability and good photo‐polymerization properties were suitable for nano‐imprint photoresists. © 2013 Society of Chemical Industry     

Synthesis and radical polymerization of 1,1,2,2-tetracyanocyclopropylstyrene

Synopsis An isomeric mixture (m-/p-: 70/30, mole/mole) of 1,1,2,2-tetracyanocyclopropylstyrene 2 was prepared by cyclopropane formation from bromomalononitrile and vinyl benzaldehyde. The substituted styrene compound 2 was polymerized with free radical initiator to obtain the polymers with multicyano functions in the pendant group. The resulting polymers were soluble in acetone and dimethyl sulfoxide (DMSO) and the inherent viscosities were in the range of 0.27–0.32 dL/g. Solution-cast films were clear and brittle, showing Tg value of 112°C.     

Kinetics studies of hybrid structure formation by controlled photopolymerization

Real-time FT-NIR spectroscopy was used to monitor the individual monomer photopolymerization kinetics within the hybrid methacrylate/vinyl ether system composed of 2-phenoxyethyl methacrylate and tri(ethylene glycol) methyl vinyl ether. Photopolymerization processing conditions, such as light intensity, photoinitiator type (both free radical and cationic) and initiator ratios and concentrations, that provide preferential direction of polymer formation based on individual monomer photopolymerization kinetics and overall conversion have been evaluated. Single source UV-light irradiation was employed to produce either single or dual-stage hybrid polymerization, validating the potential of one-step, one-pot methodology for initiating stage-curable polymerizations.     

Dimethyl Ether as a Source of Reactive Species for Alkylation of Benzene

The co-reaction of dimethyl ether and benzene has been investigated on pure and promoted-ZSM-5 catalysts at 473–773 K. It was found that the addition of benzene to dimethyl ether markedly increased the formation of toluene, xylene and C₉ aromatics on ZSM-5 at and above 623 K. This feature is attributed to the reaction of benzene with the reactive hydrocarbon species formed in the decomposition of dimethyl ether on the acidic sites of ZSM-5 zeolite. The extent of the enhancement was further increased by ZnO and Mo₂C promoters.     

亚临界二甲醚协助双单体固相接枝改性聚丙烯

以亚临界二甲醚为溶胀剂,偶氮二异丁腈(AIBN)为引发剂,在聚丙烯(PP)上接枝甲基丙烯酸缩水甘油酯(GMA)和苯乙烯(St),制备了接枝产物PP-g-(GMA-co-St).考察了溶胀时间、溶胀温度、反应时间、反应温度、St用量和引发剂用量对接枝产物相对接枝率和水接触角的影响.采用傅里叶变换红外光谱对接枝产物进行定量...     

Novel copolymerizations of methyl vinylidene cyanide with electron-rich vinyl monomers

At 28° the spontaneous reactions of methylvinylidene cyanide (MVCN) with p-methoxystyrene, p-trimethylsiloxystyrene, styrene, isobutyl vinyl ether, ethyl vinyl ether and trimethylsilyl vinyl ether yielded alternating copolymers of potential interest as new piezoelectric materials. MVCN copolymerized with vinyl acetate in low yield using radical initiator and ZnCl₂. Attempted homopolymerizations of MVCN with various initiators gave only low molecular weight oligomers, particularly trimers.     

Metal-containing initiator systems

Summary The polymerization of vinyl monomers with the initiator systems of ferrocene and acid anhydrides were investigated. The initiator activity for radical polymerization of methyl methacrylate (MMA) was higher than that for styrene (St). However, isobutyl vinyl ether was not polymerized. The rate of polymerization of MMA with ferrocene/benzoic anhydride system was in proportional to the square root concentrations of both compounds of the initiator system, indicating the mechanism of radical polymerization. When an alternating copolymer of ethylene with maleic anhydride was used as an acid anhydride, a graft copolymer, which was soluble in dimethylformamide and tetrahydrofuran, was produced from radical polymerization of MMA.     

Grafting styrene onto a polyethylene surface: A model study of an interfacial reaction

A model reactor system was assembled to study surface grafting reactions which would occur at the polymer interface in in-situ blend compatibilization using a vector fluid. The vector fluid's purpose is to convey a reactive ingredient to a blend interface and induce copolymer formation. Polyethylene (PE) was chosen as the polymer substrate, styrene monomer and/or dimethyl phthalate (DMP) as the vector fluid, and a peroxide initiator as the reactive ingredient. The free radical surface grafting reaction of styrene onto the PE surface was studied at melt processing temperature with a factorial experimental design involving the factors of time, temperature, initiator type and initiator concentration. It was found that styrene monomer was grafted at the PE substrate surface, forming a layer of PE-g-PS graft copolymer which was observed with attenuated total reflection Fourier transform infrared spectroscopy. The results indicated that the grafting reactions occurred not only at the immediate surface (2–3 μm), but also beneath the PE surface (∼ 200 μm) due to the swelling of the PE by the styrene monomer. The reaction below the immediate surface could be significantly reduced by the presence of DMP, a nonsolvent of PE; but the surface reaction was not affected. Explanations for the reaction behavior of the two different vector fluids are proposed based on the experimental results. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 427–440, 1998     

Improved Donors for the Separation of the Boron Isotopes by Gas-Liquid Exchange Reactions

Abstract

Chemical exchange between gaseous boron trifluoride (BF₃) and the liquid BF₃·dimethyl ether complex has been used extensively for the commercial fractionation of boron isotopes. Several compounds never before studied as donors in the isotope exchange reaction were examined to determine if they were viable replacements for the dimethyl ether system. For the first time, ketones were studied as donors in the boron isotope exchange reaction. The ketones examined were acetone, methyl isobutyl ketone, and diisobutyl ketone. The ideal single stage separation factors, α, measured for these ketones were between 1.038 and 1.043 at 30°C. The observed separation factor for a fourth donor system, nitromethane, was 1.067 at 30°C, well above that predicted by theory or observed for any known BF₃/donor system. For each of the systems studied, the separation factors were greater than the value of α = 1.027 reported for the dimethyl ether/BF₃ system at 30°C. In view of the experimentally observed separation factors, these donor systems are potential replacements for dimethyl ether in large-scale boron isotope fractionation schemes. It is concluded that plant size could be significantly reduced by using any of these donors rather than dimethyl ether.

     

Autoignition mechanism of dimethyl ether–air mixtures in the presence of atomic iron

The search for reactive additives capable of reducing the combustibility of dimethyl ether is an important problem due to the widening use of ether as an alternative environmentally friendly motor fuel. This paper presents a numerical study of the autoignition chemistry of mixtures of dimethyl ether with air in the presence of atomic iron. Atomic iron, which is an effective inhibitor of premixed laminar hydrocarbon flames, was found to shorten the induction period. However, the additive affects only the first stage of the induction period. The mechanism of promotion of the low-temperature oxidation of dimethyl ether–air mixtures by atomic iron is the formation of hydroxyls in reactions involving iron compounds. Since the additive hardly changes the duration of the second stage of the induction period, it can be suggested that OH radicals play an insignificant role in the low-temperature oxidation of dimethyl ether at this stage.     

Studies of moisture induced crosslinking in a novel vinyl ether-maleic anhydride copolymer

A novel vinyl ether, 2,2-dimethyl-4-vinyloxymethyl-1,3-dioxolane (DMVMD), that has a dimethyl ketal protected vicinal diol functionality, was synthesized from readily available starting materials, such as glycerol, acetone and acetylene. Copolymerisation of DMVMD with maleic anhydride (MAH) in various molar ratios was carried out using a free radical initiator. The composition of the copolymer was established by conductometric titration, and was found to be 1 : 1 irrespective of the monomer feed composition thus establishing its alternating nature. The copolymer formed clear free standing films upon solvent casting which became insoluble upon prolonged exposure to ambient atmosphere. The insolubility is ascribed to moisture induced crosslinking. A plausible mechanism for the crosslinking involves the hydrolysis of some of the anhydride groups, followed by acid catalysed deketalization, and then by the reaction of the alcoholic groups, thus generated, with the residual anhydride to give ester crosslinks. This hypothesis was confirmed both by model reactions and in situ FT-IR studies. Received: 18 November 1996/Revised: 23 January 1997/Accepted: 7 February 1997