Polymer–silica hybrids obtained by microemulsion polymerization

The styrene (St), butyl acrylate (BuA), and methyl methacrylate (MMA) polymerization in microemulsion in the presence of sodium dodecylsulfate is studied. This process is conducted in the presence of some comonomers having groups that can participate in sol–gel processes: 3(trimethyloxysilyl) propyl methacrylate (MPTS), triethoxy vinylsilane (VTES), and a comonomer with a sulfate group, styrene sodium sulfonate (StSO₃Na). It has been observed that stabile latexes are obtained by radical polymerization at pH = 7, followed by a sol–gel process in the presence of ammonia. Latex particles sizes and zeta potential grow with MTPS concentration and in StSO₃Na presence. VTES effect depends on its reactivity in St, MMA, and BuA copolymerization. Glass transition temperature and thermal decomposing temperature are influences by functional comonomer concentration and chemical structure. The Fourier transform infrared spectrum and inorganic residue growth after organic part thermal decomposition shows the presence of silica in obtained latexes.     

The Influence of Monomers upon Microemulsions with Short Chain Cosurfactant

Several monomers (i.e., acrylonitrile (ACN), ethyl acrylate (EtA), acrylate of 2 ethylhexyl (EHA), butyl acrylate (BuA), vinyl acetate (VAc), methyl methacrylate (MMA) and styrene (St)) were investigated in order to study their capacities to form microemulsions. The surfactant was nonyl phenol ethoxylate with 25 moles ethylene oxide and ethanol was used as the cosurfactant. The phase diagrams prove that the capacity for microemulsion formation varies in the following sequence: ACN = EtA > VAc > BuA > MMA > St > EHA. Conductometric and refractometric studies allowed us to evidence the formation of microemulsions with W/O, bicontinuous or O/W structure. Fluorescence studies give interesting informations on the stabilization capacity of the monomers dispersed by interaction with hydrophobic chain of the cosurfactant. H-NMR studies suggest that the monomers in microemulsions lie in regions with various polarities as function of their chemical nature. In polymerization initiated with benzoyl peroxide the minimum conversions were obtained in zones of composition where the initial microemulsions possess a bicontinuous microstructure. The reactions of degradative transfer of the increasing macroradicals account for these conversion modifications. For initiation with ammonium persulphate, its rate of decomposition depends on its ability to displace the proton bonded to the substituted vinylic carbon of the monomer. The productivity of this initiator varies within the sequence MMA > EtA > BuA > St > ACN > VAc. The consumption of the initiator, as induced by the monomer, depends on its chemical nature and on the solubilization site of the microemulsions.     

Styrene and Butyl Acrylate Polymerization in Nonionic Microemulsions in Presence of Layered Silicates

It was studied the polymerization of styrene (St) and of butyl acrylate (BuA) in nonionic microemulsions in the presence of a layered alumino silicates, montmorilonit (MMT) type. In time, the latexes separate in two distinct strata, MMT being distributed in the inferior strata where forms aggregates with on order of size bigger than the diameters of nanoparticles of latex. The solid products obtained are nanohybrids of intercalate type whose structural order increases direct proportional with the increase of hydrophobic character of the quaternary ammonium salts used for organophilization of MMT. The presence of nonionic surfactant, nonyl phenol with 25 mols of ethylene oxide, intercalated between the lamellar strata of MMT produces the decrease of thermal stability of hybrids and decreases the glass transition temperature of PSt which is more compatible than PBuA.     

乳液共聚反应过程与聚合物结构关系及~（13）C－NMR对聚合物结构的表征

用间歇法和半连续法进行了丙烯酸丁酯（ＢｕＡ）与醋酸乙烯酯（ＶＡｃ）乳液共聚合．１３Ｃ－ＮＭＲ对共聚产物分子结构测试表明，在间歇法共聚合中随着反应进行其组成及结构发生很大变化，而半连续法确能制得成份及结构均匀一致的Ｐ（ＢｕＡ－ＶＡｃ）共聚物．由于ＢｕＡ水溶性小于ＶＡｃ，而其竟聚率远大于ＶＡｃ，间歇法共聚合反应初期只有少量ＶＡｃ参加共聚合．通过对间歇法共聚合中不同反应时间聚合物的１３Ｃ－ＮＭＲ测试，表明反应初期聚合的ＶＡｃ以单链节或二元序列形式存在于主要由ＢｕＡ单元构成的分子链中，而并未形成较长ＶＡｃ链段．对上述试样玻璃化转变温度的测试结果与１３Ｃ－ＮＭＲ实验结果颇为一致．     

Reactivity Ratios for Microemulsion Copolymerization of N-butyl Maleimide and Styrene

The oil-in-water microemulsion containing N-butyl maleimide(NBMI, M1) and styrene(St, M2) was prepared. The complexation properties of NBMI and St in microemulsion were investigated by means of 1H-NMR. With the participation of charge-transfer complex(CTC), four reactivity ratios and the relative reactivity of free monomers and CTC were obtained. The result was compared with that measured by Mayo-Lewis method.     

Reactivity Ratios for Microemulsion Copolymeriration of N-butyl Maleimide and Styrene

IntroductionReactivityratioscanofferthemessageofrelativereactivityofcomonomers.TWomonomerreactivityratioscanbeacquiredfromtheend-groupmodelproposedbyMayoandLewis,howevef,thereareonlyapparentreactivityratiosavailablefromthiskineticmodelwhencharge-transfercomplex(CTC)participatesinthecopolymerization.Therefore,thecopolymeriZationinwhichCTCexistsisworthyoffurtherresearch.Sofar,therearethreekineticmodelsofcopolymerizationwiththeparticipationofCTCinall,namely,SeinerandLittmodel',Shirotamodel…     

粒径可控阳离子型聚苯乙烯纳米粒子的制备及表征

在采用阳离子型双子（gemini）表面活性剂作为乳化剂,不使用任何助乳化剂的条件下,通过改进微乳液聚合工艺制备了窄分布粒径可控的阳离子型聚苯乙烯（PS）纳米乳液。 改进微乳液聚合的主要特点是：大部分苯乙烯以预乳液的形式恒速滴入引发聚合的微乳液中,使用具有高乳化性能的gemini表面活性剂作为乳化剂能明显降低乳胶粒粒径。 实验结果表明,少量阳离子单体三甲基烯丙基氯化铵作为共聚单体能够明显减小Z均粒径、降低粒度分布,乳化剂用量、引发剂用量和反应温度均能影响制备乳胶粒的粒径及其粒度分布。 乳化剂和引发剂用量分别为苯乙烯质量的5%~10%和1.0%~1.5%、反应温度为70~75 ℃时,能够制备粒径小分布窄的阳离子型聚苯乙烯纳米粒子。 Z均粒径与苯乙烯质量之间的线性关系表明,Z均粒径可以通过苯乙烯用量来控制。 不同聚合工艺下制备的聚合物粒度分布曲线表明,改进微乳液聚合工艺（半连续预乳化工艺）在制备窄分布的聚合物纳米粒子方面具有很强的优越性。     

Interaction of sodium ions with cationic surfactant interfaces

The thermodynamically stable microemulsion and lamellar phases in the didodecyldimethylammonium bromide/water/n-decane ternary system were explored in the presence of NaBr to gain information on sodium ion-interface interactions. Experimental results, obtained by different NMR techniques, strongly suggest accumulation of sodium ions at the cationic interface. This apparently counterintuitive result is explained by invoking the dispersion potential experienced by the ions near the interface. A mechanism is proposed that can account for the dramatic shrinkage of the microemulsion phase region when an electrolyte is added.     

丙烯酸酯及苯乙烯微乳体系的相行为及微乳聚合

甲基丙烯酸甲酯;十二烷基磺酸钠;十二烷基磺酸钠;丙烯酸酯及苯乙烯微乳体系的相行为及微乳聚合     

N-丁基马来酰亚胺/苯乙烯微乳液共聚合研究

研究了氘代氯仿中Ｎ－丁基马来酰亚胺（ＮＢＭＩ）和苯乙烯（Ｓｔ）的络合性能。以十二烷基硫酸钠（ＳＤＳ）和正戊醇（ＰＴＬ）为复合乳化剂,配制了含有ＮＢＭＩ（Ｍ１）和Ｓｔ（Ｍ２）的Ｏ／Ｗ微乳液。用过硫酸钾引发该体系进行微乳液共聚合。固定乳化剂的浓度为〔ＳＤＳ〕＝０．２１ｍｏｌ／Ｌ,〔ＰＴＬ〕＝０．２８ｍｏｌ／Ｌ,详细研究了聚合温度、单体配比和引发剂用量对共聚合动力学的影响。用元素分析法确定共聚物的组成,     

Separation of Six Pyridoncarboylxic Acid Derivatives by Micellar and Microemulsion Electrokinetic Chromatography

Micellar electrokinetic chromatography (MEKC) and microemulsion electrokinetic chromatography (MEEKC) are two kinds of electrokinetic capillary chromatography (EKC), which are characterized of high solubilization capacity and separation efficiency. In our previous work, some polar organic compounds and hydrophobic neutral compounds were separated successfully by EKC1-3. In this paper, these methods were used for separating six pyridoncarboylxic acid derivatives with similar structures. T…     

微乳液毛细管电动色谱研究

本文研究了两组混合样的微乳液毛细管电动色谱(MEEKC)分离, 较系统地研究了微乳液的内相, 助表面活性剂及其浓度对电动分离的迁移时间、柱效及时间窗的影响, 并与胶束毛细管电动色谱(MEKC)分离进行了比较, 选用由80mmol/L正辛烷-120mmol/L十二烷基硫酸钠-900mmol/L正丁醇-10mmol/L硼砂组成的微乳液, 样品组分电动色谱迁移时间的RSD<0.8%, 峰面积RSD<3.0%.     

Surface modification of aluminium with reactive microgels

The adsorption and organisation process of reactive microgels has been investigated on technical aluminium. The aim was to replace the present chromating procedure on reactive metals like aluminium because this process was been considered as an ecological problem. By means of a two‐step emulsion polymerization with phosphate substituted monomer we have obtained polymeric nano‐particles with phosphate groups on the surface. The core is synthesized by copolymerization from styrene (St) and butyl acrylate (BuA). The results of several analytical methods like contact angle SEM or TEM measurements showed, that these microgels were able to adsorb spontaneously onto the substrate surface and subsequently a structured molecular order was formed. The properties of the adsorbed microgel layers were confirmed by industrial linked adhesion and corrosion tests.     

Ternary microemulsions of vinylic and acrylic monomers

Ternary systems consisting of sodium dodecyl sulfate (SDS) as surfactant, water and several vinyl and acrylic monomers [vinyl acetate (VAc), acrylonitrile (ACN), ethyl acrylate (EtA), butyl acrylate (BuA), 2-ethylhexyl acrylate (EHA), methyl methacrylate (MMA), butyl methacrylate (MMB) and styrene (St)] were studied. The solubilization of monomer in aqueous solutions of SDS was found to be dependent on its structure and concentration. The molar specific solubility was observed to decrease with hydrophobicity and increase with polarity of monomer, that is, it was lowest for St, EHA and highest for MMA, EtA. The NMR and fluorescence studies indicate that solubilization occurred at a different domain of the interfacial layer. The hydrophobic monomers are solubilized toward the hydrocarbon interior of the micelles whereas the hydrophilic ones, toward the hydrated tail of the surfactant. The penetration of monomers into the oil-in-water interface is limited because the screening of charged ions of emulsifier is not operative. A relationship between the persulfate initiator decomposition rate and the lability of the α-hydrogen linked to the substituted carbon of the double bond was established. The initiator productivity was the highest for MMA (lacking such α-hydrogen) and the lowest for VAc and St, the monomers in which the C-H_α bond is the most reactive.     

Transport of alkali-metal picrates through liquid membranes: Coupled action of w/o microemulsion droplets and lipophilic crown-ether carriers

The transport of potassium and sodium picrates is measured by a liquid membrane technique in the presence of two mobile carriers: water-in-oil microemulsion droplets and lipophilic crown-ethers. The fluxes are compared for two cases: (i) the crown-ether (dicyclohexano-18-crown-6 is assumed to be independent of the microemulsion droplet and (ii the crown-ether (dodecano- 18-crown-6) is assumed to be anchored in the droplet. A lower flux is observed when the microemulsion droplet and the crown-ether diffuse as a single entity. These results suggest that larger synergistic effects are obtained when the extractant can diffuse independently of the microemulsion droplet.     

Hybrid polymer inorganic materials prepared from ternary microemulsions

The microemulsion system containing vinyl acetate (Vac), silane derivatives tetraethoxysilane (TEOS), methacryloxypropyltrimethoxysilane (MPTS), vinyltriethoxysilane (VTES), methyltriethoxysilane (MeTES), octyltriethoxysilane (OTES), nonylphenol etoxylated with 25 mol of ethylene oxyde (NPEO₂₅) and water was studied. It was established that the probability of microemulsion formation increases with surfactant concentration. The microenviroment of the solubilization of the VAc and of silane derivatives in the aggregates of NPEO₂₅ was affected by their polarity. Hybrid materials were obtained by sol-gel reaction of silane derivatives combined with free-radical polymerization of VAc. The change of the glass transition temperature and of thermal stability of the polymer chains in the presence of the inorganic one proved the formation of simultaneous polymer inorganic hybrids.     

Extraction of cobalt by the AOT microemulsion system

The extraction of cobalt by Winsor II microemulsion system was studied. In the bis (2-ethylhexyl) sulfosuccinate sodium salt (AOT)/n-pentanol/n-heptane/NaCl system, AOT was used as a anionic surfactant to form microemulsion in n-heptane, n-pentanol was injected in the microemulsion as a cosurfactant. Co(II) was found to be extracted into the microemulsion phase due to ion pair formation such as Co²⁺(R–SO₃ ⁻)Cl. The influence of different parameters such as the volume ratio of aqueous phase to microemulsion, surfactant concentration, pH of the feed solutions, cosurfactant concentration as well as temperature on the extraction yield (E%) were investigated. The results showed that it was possible to extract 95% of cobalt by the AOT Winsor II microemulsion.     

Variation of surface properties and textural features of spinel ZnAl2O4 and perovskite LaMnO3 nanoparticles prepared via CTAB-butanol-octane-nitrate salt microemulsions in the reverse and bicontinuous states

Two binary oxides, a spinel, ZnAl2O4, and a typical perovskite, LaMnO3, have been prepared via CTAB-1-butanol-n-octane-nitrate salt microemulsion in the reverse and bicontinuous states. The exact point of the reverse and bicontinuous states of the microemulsion used in the synthesis was determined by conductivity experiments. The materials obtained after heating at 800 degrees C were characterized by XRD analysis for their crystal structure, N2 porosimetry for their surface area and porosity, and SEM and TEM photography for their texture. The ZnAl2O4 spinel obtained via the reverse microemulsion appears in SEM in a more fragmented form and with a higher specific surface area (143.7 m(2)g(-1)), compared to the corresponding solid prepared via the bicontinuous microemulsion, which appears more robust with lower surface area (126.7 m(2)g(-1)). Nevertheless both materials reveal in TEM a sponge-like structure. The perovskite materials LaMnO3 prepared via the reverse microemulsion showed in SEM a peculiar doughnut-like texture, each doughnut-like secondary particle having a diameter of 2 microm. The corresponding sample developed via the bicontinuous microemulsion showed in SEM uniform secondary particles of size approximately 0.2 microm. Both perovskite samples LaMnO3 appear well crystallized with relative low surface areas, 23.7 m(2)g(-1) for the reverse sample and 10.9 m(2)g(-1) for the bicontinuous one. The TEM photographs reveal that both of them, of reversed and bicontinuous origin, are made up of primary nanoparticles in the size range 40-100 nm. In SEM those materials showed a different secondary structure.     

Iron-mediated AGET ATRP of styrene and methyl methacrylate using ascorbic acid sodium salt as reducing agent

Atom transfer radical polymerization of styrene(St) and methyl methacrylate(MMA) in bulk and in different solvents using activators generated by electron transfer(AGET ATRP) were investigated in the presence of a limited amount of air using FeCl3·6H2O as the catalyst, ascorbic acid sodium salt(AsAc-Na) as the reducing agent, and a cheap and commercially available tetrabutylammonium bromide(TBABr) as the ligand. It was found that polymerization in THF resulted in shorter induction period than that in bulk and in toluene for AGET ATRP of St, while referring to AGET ATRP of MMA, polymerization in THF showed three advantages compared with that in bulk and toluene: 1) shortening the induction period, 2) enhancing the polymerization rate and 3) having better controllability. The living features of the obtained polymers were verified by chain end analysis and chain-extension experiments.     

Physicochemical investigations of microemulsification of eucalyptus oil and water using mixed surfactants (AOT+Brij-35) and butanol

Microemulsification of a vegetable oil (eucalyptus) with single and mixed surfactants (AOT and Brij-35), cosurfactant of different lipophilicities (isomers of butanol), and water were studied at different surfactant and cosurfactant mixing ratios. The phase diagrams of the quaternary systems were constructed using unfolded and folded tetrahedron, wherein the phase characteristics of different ternary systems can be underlined. The microemulsion zone was found to be dependent upon the mixing ratios of surfactant and cosurfactant; the largest microemulsion zone was formed with 1:1 (w/w) S:CS. The effects of temperature and additives (NaCl, urea, glucose, and bile salts of different concentrations) on the phase behavior were examined. The mixed microemulsion system showed temperature insensitivity, whereas the Brij-35 (single) stabilized system exhibited a smaller microemulsion zone at elevated temperature. NaCl and glucose increased the microemulsion zone up to a certain concentration, beyond which the microemulsion zones were decreased. These additives decreased the microemulsion zones as temperature was increased. The effect of urea on microemulsion zone was found to be insignificant even at the concentration 3.0 mol dm(-3). Little effect on microemulsion zone was shown by NaC (sodium cholate) at 0.25 and 0.5 mol dm(-3) at different temperatures. The conductance of the single (AOT) and mixed microemulsion system (AOT+Brij-35) depends upon the water content and mixing ratios of the surfactants, and a steep rise in conductance was observed at equal weight percentages of oil and water. Viscosities for both single (AOT) and mixed (AOT+Brij-35) surfactant systems passed through maxima at equal oil and water regions showing structural transition. The viscosities for microemulsion systems increased with increasing Brij-35 content in the AOT+Brij-35 blend. Conductances and viscosities of different monophasic compositions in the absence and presence of additives (NaCl and NaC) were measured at different temperatures. The activation energy of conduction (DeltaE(cond)( *)) and the activation enthalpy for viscous flow (DeltaH(vis)( *)) were evaluated. It was found that both DeltaE(cond)( *) and DeltaH(vis)( *) were a function of the nature of the dispersion medium. Considering the phase separation point of maximum solubility, the free energy of dissolution of water or oil (DeltaG(s)(0)) at the microdispersed state in amphiphile medium was estimated and found to be a function of surfactant composition.