Hollow-fiber membranes coated with polymerizable bicontinuous microemulsions

A new method has been successfully employed to prepare hollow-fiber membranes by coating and polymerizing bicontinuous microemulsions onto the internal surfaces of hollow-fiber membranes. The bicontinuous microemulsion consisting of water, a polymerizable zwitterionic surfactant of acryloyloxyundecyl dimethylammonio acetate, methyl methacrylate, and 2-hydroxylethyl methacrylate (HEMA) can form a transparent polymer thin film after polymerization. The hollow-fiber membranes as the supports for microemulsion coatings were fabricated from the spinning solution of polyethersulfone/diethylene glycol/N-methyl-2-pyrrolidone. The microemulsion coated hollow-fiber membranes were evaluated by the separation efficiency and the permeation rate of polyethylene glycol (PEG) solutions. The performance of coated membrane on the PEG separation is strongly dependent on the concentration of HEMA and water in precursor bicontinuous microemulsions. The pore size of the hollow-fiber membranes can be regulated between about 2 to 40 nm by varying the composition of precursor bicontinuous microemulsions. The characteristics of the coated membranes is believed to be directly related to the bicontinuous structures of precursor bicontinuous microemulsions. The use of polymerizable bicontinuous microemulsions enable one to better control the microstructures of coated membranes via in situ polymerization.     

微乳液聚合制备透明丙烯酸酯多孔共聚物

多孔聚丙烯酸酯;引发;微乳液聚合制备透明丙烯酸酯多孔共聚物     

双连续相微乳液辐射聚合制备多孔材料的研究

利用6 0 Co γ射线在室温下辐照双连续相微乳液体系以制备多孔聚合物材料 ,试图在控制多孔材料的微孔结构形态和减少微乳液聚合过程中的相分离方面做一些探索 .通过电导率的测量分析微乳液的结构类型 ,并确定微乳液的双连续相区域范围 .微乳液聚合后所得的样品的孔结构和聚合前的微乳液结构类型有关 ,扫描电镜和热重分析的结果表明双连续相微乳液在聚合时容易发生相分离 ,未必能够得到开孔结构的聚合物 .但适当控制聚合前微乳液的组成 ,如选择合适的水油比例、交联剂的用量和加入一些功能性单体 (如甲基丙烯酸或丙烯酸钠 ) ,可以有效地抑制相分离 ,调节所得聚合物的结构形态 .     

Monitor of Polymerization of Inverse Microemulsions Containing Methyl Methacrylate and Acrylic Acid

Microemulsions are isotropic, optically transparent and thermodynamically stabledispersion systems consisting of water, oil and suitable surfactants. Polymerization inmicroemulsions has been widely studied since 1980s, which can be divided intooil-in-wate…     

Polymerization of w/o microemulsions for the preparation of transparent SiO2/PMMA nanocomposites

Reverse w/o microemulsions composed of methyl methacrylate (MMA) forming the oil phase, nonionic surfactants, and water are used for the synthesis of transparent SiO2/PMMA nanocomposites. An inorganic precursor, tetraethoxysilane (Si(OEt)(4), TEOS), is hydrolyzed in the reverse micelles containing aqueous ammonia. During the hydrolysis of TEOS, polymerization of the continuous MMA phase is initiated using AIBN (azobisisobutyronitrile), and after thermal polymerization at 333 K for 12 h, solid blocks of PMMA are obtained in which nanometer-sized silica particles are trapped in the solid polymer matrix. According to small-angle X-ray and dynamic light scattering experiments, the water droplets in MMA microemulsions are 12 nm (R(W) = 13) in diameter, whereas after polymerization of the microemulsion, the SiO2 particles in the transparent SiO2/PMMA composites are 26 nm in diameter. Transmission electron micrographs demonstrate a low degree of agglomeration in the composites. In comparison with materials generated from micelle-free solutions, the particle size distribution is narrow. The reverse micelle-mediated approach produces composites of high transparency comparable with that of pure PMMA.     

Polymerization of water-in-oil microemulsions: Methyl methacrylate,acrylic acid,and sodium acrylamidostearate

Water-in-oil (w/o) microemulsions of methyl methacrylate (MMA), acrylic acid (AA), sodium acrylamidostearate (NaAAS), and water were investigated. MMA, AA, and NaAAS could be terpolymerized in these microemulsions. For a composition of 54% MMA, 34% AA, 2% NaAAS, and 10% H₂O, polymers of high molecular weights of about 1,000,000 were obtained between 3.5 to 24% polymer conversion. The system became a transparent gel when conversion exceeded 36%. Transparent solid terpolymer containing water up to 16% were also obtained after fully polymerizations of certain compositions.     

微乳液结构的研究

测定了十二烷基磺酸钠／正丁醇／２０％苯乙烯／水体系的相平衡，用冷冻刻蚀、ＥＳＲ、ＦＴ－ＩＲ研究了上述体系微乳液的结构，研究表明，苯乙烯含量恒定时，随着体系中水含量增加，电导确定的双连续结构的微乳液经历着从油包水到以连续再到水包油变化，ＦＴ－ＩＲ测定表明，Ｗ／Ｏ微乳兴较Ｏ／Ｗ微乳液的ＯＨ伸缩振动和弯曲振动频率有显著减小，说明Ｗ／Ｏ微乳兴中氢键缔合要比Ｏ／Ｗ强得多。ＥＳＲ测定表明Ｏ／Ｗ微乳液的旋转相关     

Microemulsion polymerization of acrylamide and styrene: Effect of the structures of reaction media

Isothermal phase diagrams of the system cetyltrimethylammonium bromide (CTAB)/n‐butanol/n‐octane/water were constructed, and the effect of the oil (n‐octane) contents on the microemulsions was studied at 40 °C. We determined the microemulsion structures of two systems, CTAB/n‐butanol/10% n‐octane/water and sodium dodecyl sulfonate (As)/n‐butanol/20% styrene/water, by conductivity measurements to investigate the polymerization of acrylamide and styrene in the two microemulsion systems. The polymerization kinetics of the water‐soluble monomer acrylamide in CTAB micelles and the different CTAB/n‐butanol/10% n‐octane/water microemulsion media [water‐in‐oil (W/O), bicontinuous (BC), and oil‐in‐water (O/W)] were studied with water‐soluble sodium bisulfite as the initiator. The maximum polymerization rate in CTAB micelles was found at the second critical micelle concentration. A mechanism of polyacrylamide formation and growth was proposed. A connection between the structures of the microemulsions and the polymerization rates was observed; the maximum polymerization rate occurred at two transition points, from W/O to BC and from BC to O/W, and the polyacrylamide molecular weights, which depended on the structures of the microemulsions, were also found. A square‐root dependence of the polymerization rates on the initiator concentrations was obtained in CTAB micelles and O/W microemulsion media. The polymerization of the oil‐soluble monomer styrene in different As/n‐butanol/20% styrene/water microemulsion media (W/O, BC, and O/W) was also investigated with different initiators: water‐soluble potassium persulfate and oil‐soluble azobisisobutyronitrile. A similar connection between the structures of the microemulsions and the conversions of styrene in CTAB/n‐butanol/10% n‐octane/water for the polymerization of acrylamide was observed again. The structures of the microemulsions had an important role in the molecular weights and sizes of polystyrene. The polystyrene particles were 10–20 nm in diameter in BC microemulsion media and 30–60 nm in diameter in O/W microemulsion media according to transmission electron microscopy. We determined the solubilization site of styrene in O/W microemulsion drops by ¹H NMR spectra to analyze the results of the microemulsion polymerization of styrene. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3320–3334, 2001     

Poly(phenyl methacrylate) and poly(1‐naphthyl methacrylate) prepared in microemulsions

Phenyl methacrylate and 1‐naphthyl methacrylate were polymerized in microemulsions using stearyltrimethylammonium chloride, cetyltrimethylammonium bromide, and a mixture of nonionic Triton surfactants to form latexes that were 20–30 nm in diameter. A temperature of 70 °C was needed to obtain polymers using thermal initiation. The tacticities of poly(phenyl methacrylate) (PPhMA) (55% rr) and poly(1‐naphthyl methacrylate) (P‐1‐NM) (47% rr) were the same as those of the polymers prepared in toluene solutions. The weight average molecular weights were 1 × 10⁶ and 5 × 10⁵ g/mol for PPhMA and P‐1‐NM prepared in microemulsions with very broad distributions. PPhMA samples from microemulsions and solution had the same T_g = 127 °C. P‐1‐NM from microemulsions had T_g = 145–147 °C compared with T_g = 142 °C for P‐1‐NM from solution. The molecular weights and the glass‐transition temperatures of both PPhMA and P‐1‐NM from microemulsions are substantially higher than any previously reported. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 519–524, 2001     

Effect of the structures of microemulsions on chemical reactions

Two kinds of chemical reactions were studied in two different microemulsion systems: cetyltrimethylammonium bromide/1-butanol/10 and 25% n-octane/water and sodium dodecyl sulfonate/1-butanol/20% styrene/water. One reaction is a hydrolysis reaction, in which aspirin and 2,4-dinitrochlorobenzene were used as the hydrolysis substrates. The second reaction is the polymerization of styrene, which was initiated by using two initiators, water-soluble K₂S₂O₈ and oil-soluble 2,2′-azobis(isobutyronitrile), and, at the same time, the polymerization of acrylamide, which was initiated by NaHSO₃, was also studied. All the hydrolysis reaction experimental results show that the hydrolysis is greatly affected by the structures and the structural transitions of microemulsions. The hydrolysis rates are higher in water-in-oil (W/O) microemulsion media and decrease with the addition of water. The rates increase in bicontinuous (BC) microemulsions and decrease in oil-in-water (O/W) microemulsions. The transition points of the hydrolysis rates occurred at the two microemulsion structural transition points from W/O to BC and from BC to O/W. The polymerization relationships between the conversions of styrene, the molecular weights of polystyrene and the water contents of the microemulsion system were obtained. The effects of microemulsion structures on the sizes of the polystyrene particles and on the molecular weights of the polymers are discussed. Polystyrene particles with diameters of 10–60 nm were observed by microscopy. Our experimental polymerization results show that microemulsions are suitable as media for the production of polymers, the molecular weights and the particle sizes of which can be controlled and predicted by variations in microemulsion structures. Received: 11 July 1999/Accepted: 26 July 1999     

A fast convenient method to prepare hybrid sol-gel materials with low volume-shrinkages

We present a simple and fast method for the synthesis of polyacrylates-silica hybrid materials with significantly low volume shrinkages through the sol-gel reactions of tetraethyl orthosilicate and 2-hydroxyethyl methacrylate along with the free-radical polymerization of the acrylate monomer. The volume shrinkage from the processible sol to the final product was about 6–20% for the hybrid materials having the silica contents up to about 50 wt-%. As a result of the low shrinkage, crack-free, transparent and monolithic hybrid materials of relatively large sizes can be prepared within a short period of 6 to 12 hours. The formation of covalent bonding between the organic and the silica components in the hybrid materials was demonstrated. Thermal stability of the polyacrylate component in the hybrid materials were found to be higher than that of the bulk polymer. Other vinyl polymers such as poly(methyl methacrylate) and polyacrylonitrile have also been incorporated into the inorganic silica sol-gel matrix by using this method.     

Polymerization of Methyl Methacrylate and Isobutyl Methacrylate in Ternary-Component Emulsions and Microemulsions: Effect of Surfactant Concentration

Abstract

The similarities and differences in the polymerization of MMA (methyl methacrylate) and iBMA (isobutyl methacrylate) in a ternarycomponent system have been investigated from a turbid emulsion to a transparent microemulsion by increasing the surfactant concentration. In spite of the difference in the solubilities of these two monomers in the aqueous phase, the rate dependencies on the surfactant concentration of both monomers were found to be about 0.30 for the emulsion polymerization and about 0.60 for the microemulsion polymerization with monomer concentrations higher than 5 wt%. However, at a low monomer concentration (3 wt%), different negative rate dependencies of ?0.93 and ?1.20 were obtained for microemulsion polymerization of MMA and iBMA, respectively. The results are discussed in terms of particle nucleation mechanisms.     

Polymerization from the surface of single-walled carbon nanotubes - preparation and characterization of nanocomposites

Single-walled carbon nanotubes were functionalized along their sidewalls with phenol groups using the 1,3-dipolar cycloaddition reaction. These phenols could be further derivatized with 2-bromoisobutyryl bromide, resulting in the attachment of atom transfer radical polymerization initiators to the sidewalls of the nanotubes. These initiators were found to be active in the polymerization of methyl methacrylate and tert-butyl acrylate from the surface of the nanotubes. However, the polymerizations were not controlled, leading to the production of high molecular weight polymers with relatively large polydispersities. The resulting polymerized nanotubes were analyzed by IR, Raman spectroscopy, DSC, TEM, and AFM. The nanotubes functionalized with poly(methyl methacrylate) were found to be insoluble, while those functionalized with poly(tert-butyl acrylate) were soluble in a variety of organic solvents. The tert-butyl groups of these appended polymers could also be removed to produce nanotubes functionalized with poly(acrylic acid), resulting in structures that are soluble in aqueous solutions.     

微乳液催化苯乙烯聚合反应

微乳液催化苯乙烯聚合反应１）郝京诚汪汉卿２）（中国科学院兰州化学物理研究所兰州７３００００）石元昌李干佐（山东大学胶体与界面化学研究所济南２５０１００）关键词微乳液催化苯乙烯聚合微乳液［１］是油、水、表面活性剂和助表面活性剂在适当比例下自发形成的热力...     

Sugar-based microemulsion glass templates

Complex fluids comprising of surfactants with water and/or oil form a rich variety of dynamic self-assembled structures, ranging from spherical swollen micelles, viscous rod-like micelles, and bicontinuous microemulsions to ordered liquid crystalline phases. The wide range of practical and specialized applications of complex fluids has made them the subject of intense research for many decades. Here, we demonstrate for the first time how bicontinuous microemulsions containing equal masses of oil and sugar can be driven to the glassy state without phase separation at ambient temperatures by controlled desiccation of sugar-rich microemulsions. The robust nanostructure of these microemulsion glasses allows polymerization of hydrophobic liquid monomers within the interstices of the glassy microemulsion template without macroscopic phase separation. Yet after polymerization, the sugar and surfactant template can be easily removed by dissolution in water.     

Microemulsion polymerization: phase behavior driven mechanistic changes

We have examined the phase behavior of anionic microemulsions of the general type water/NaCl–hexyl methacrylate (C₆MA)-bis(2-ethylhexyl)sulfosuccinate (AOT)/sodium dodecyl sulfate (SDS) with respect to temperature and composition. Monomer partitioning measurements and kinetic experiments show good agreement with the Morgan model (de Vries et al. in Macromolecules 34:3233, 2001) for droplet-type microemulsions that do not phase separate as monomer is consumed. In contrast, balanced microemulsions, which efficiently solubilize large amounts of monomer, exhibit dramatic effects on the polymerization kinetics as the phase behavior changes. Our findings suggest that the appearance of a liquid crystalline mesophase in the binary water–surfactant system of the respective microemulsion causes a phase separation during polymerization and, thus, a severe deviation from previous mechanistic models.     

微乳液中苯乙烯聚合反应的研究

测定了十二烷基磺酸钠(As)/正丁醇/20%苯乙烯/水体系相平衡。用油溶性偶氮二异丁腈(AIBN)和水溶性过二硫酸钾(K~2S~2O~8)为引发剂,研究了油包水(W/O)、双连续(BC)和水包油(O/W)型微乳液介质中苯乙烯的聚合反应。得到了苯乙烯转化率和聚苯乙烯分子量与体系水含量之间的关系,讨论了微乳液结构对聚合作用的影响。并通过电镜观察了聚苯乙烯的形貌,求得了聚苯乙烯的粒径,同时用^1HNMR研究了苯乙烯在微乳液液滴中的增溶位置,分析了聚合作用的实验结果。     

有机硅聚丙烯酸酯微乳液的合成与性能

有机硅聚丙烯酸酯微乳液的合成与性能;硅氧烷     

离子液体对甲基丙烯醛氧化酯化反应的影响

异丁烯氧化制备甲基丙烯酸甲酯(MMA)是一条极具优势、清洁高效的工艺技术路线.但甲基丙烯酸甲酯极易聚合^[1],故异丁烯三步法及传统的丙酮氰醇法均在酯化过程中加入对苯二酚、对羟基苯甲醚、2,4-甲基-6-叔丁基苯酚等有机物作为阻聚剂^[2].而甲基丙烯醛直接氧化酯化为MMA时,碱性和加热的反应条件使MMA更易聚合^[3].因而防止MMA在反应过程中的聚合成为工艺技术的关键问题.本文在甲基丙烯醛一步氧化酯化生成MMA的反应体系中添加离子液体1-丁基-3-甲基咪唑六氟磷酸盐([bm im]PF₆),结果表明,该离子液体既能提高MMA的选择性还有效防止MMA的聚合.     

高透明抗冲聚苯乙烯树脂的辐射合成与性能表征

以过氧化苯甲酰为引发剂,采用苯乙烯、甲基丙烯酸甲酯为共聚单体,先经本体自由基预聚合,再经γ辐照聚合法合成甲基丙烯酸甲酯 苯乙烯共聚物(MS)树脂.系统研究了吸收剂量和剂量率对MS树脂的分子量及其分布的影响,同时研究了树脂的化学结构、热性能、透过率和力学性能.结果表明,辐射合成的MS树脂是一种无规共聚物,具有很好的光学性能,较好的韧性和强度.