聚氨酯类反应型高分子表面活性剂的研究进展

反应型高分子表面活性剂兼有反应型表面活性剂可以以牢固的共价键键合到聚合物粒子上,有效避免了表面活性剂在聚合物膜中迁移的优点和高分子表面活性剂性质稳定、耐水性好、低毒或无毒的优点,是一种备受关注的新型表面活性剂,其中含有双键的聚氨酯类可聚合型高分子表面活性剂因其软硬度可调、反应活性高等优点而成为此类研究的一个新热点。本文综述了国内外聚氨酯类反应型高分子表面活性剂最新研究概况,简述了其合成路线和应用性能,并对未来的研究方向进行了预测。     

高分子表面活性剂的合成

介绍了高分子表面活性剂的合成方法及其不同于低分子表面活性剂的特点,重点从离子聚合、活性自由基聚合、缩合聚合、开环聚合、高分子化学反应、自由基胶束聚合等角度综述了近几-来高分子表面活性剂的合成研究进展.     

介观模拟方法研究高分子表面活性剂在水介质中的聚集行为

高分子表面活性剂已广泛应用于许多领域, 其构型复杂、分子量大等特点使其聚集行为不同于小分子表面活性剂. 从微观上认识其聚集行为可为应用提供指导, 因而此方面的研究倍受关注. 计算机模拟技术的发展使我们能成功地在微观或介观水平上获得高分子表面活性剂聚集行为的信息. 本文综述了耗散粒子动力学(DPD)和介观动力学(MesoDyn)在高分子表面活性剂聚集行为研究中的应用. 着重介绍了这两种介观模拟方法研究单一高分子表面活性剂溶液的相行为及其与低分子表面活性剂之间的相互作用, 揭示了实验中难以观测的微观相分离及聚集体结构形态的变化规律. 这些信息可以为实验研究提供指导和补充.     

CMC系列高分子表面活性剂与原油超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达2835mN/m,界面张力达到10^-110mN/m.碱的加入可显著降低高分子表面活性剂与原油的界面张力,在适当条件下界面张力达到超低值(10^-3mN/m),可望作为三次采油的驱油剂.等效烷烃模型研究表明,用碱与原油酸性组分的作用来解释碱能使界面张力下降至超低值的传统观点是不完善的,加入碱能使高分子表面活性剂胶束解缔,胶束数量增多,胶束粒径减小,单分子自由链增加,有利于高分子表面活性剂向界面迁移和排布,这是高分子表面活性剂和碱复配体系与原油界面张力下降至超低值的主要原因.     

高分子表面活性剂的分子设计

简要讨论高分子表面活性剂的俣成和表征方法，分析了在水溶液中两亲性聚合分子形态与表面活性的关系，单分子／多分子胶束多的形成是导致聚合物表面活性变差的主要因素，提出了高分子表面活性剂的分子设计原则，设计了多种在高分子量下将能够优质优良表面活性的高分子表面活性剂分子结构模型。     

表面活性剂与高分子链混合体系的模拟

计算机模拟了高分子链对表面活性剂胶束形成过程的影响，以及高分子链构象性质随胶束化过程的变化.结果表明,当高分子链与表面活性剂之间的相互作用强度超过临界值后，高分子链的存在有利于表面活性剂胶束的形成.临界聚集浓度（CAC）与临界胶束浓度（CMC）的比值CAC/CMC随高分子链长的增大和相互吸引作用的增强而减小.在CAC之前，高分子链与表面活性剂分子只有动态的聚集；但在CAC之后，表面活性剂胶束随表面活性剂浓度X的增加而增大，并静态地吸附在高分子链上，形成表面活性剂/高分子聚集体.随着表面活性剂分子的加入，高分子链的均方末端距和平均非球形因子先保持恒定；从X略小于CAC开始， 和快速减小，至极小值后又逐渐增大.模拟结果支持高分子链包裹在胶束表面的实验模型.     

有机硅、氟高分子表面活性剂在建材中的应用发展

综述了有机硅、含氟高分子表面活性剂及含有机硅氟的高分子表面活性剂的种类和研究进展,介绍了它们在涂料工业、塑料工业等建材领域中的应用。     

新型非离子性嵌段型聚氨酯表面活性剂的合成及其表面活性研究

本文以异佛尔酮二异氰酸酯、聚醚为主要原料,通过逐步聚合得到新型非离子性两、三嵌段型聚氨酯表面活性剂(Di/Tri-PUn),使用红外光谱及1HNMR对其结构进行了表征,并用表面张力仪对其表面活性进行了测定。实验结果表明,所制备出的六种非离子性两、三嵌段型聚氨酯表面活性剂均具有较低的临界胶束浓度(其中Di-PUn系列临界胶束浓度数量级可达10-6),产物Di-PU34水溶液在室温下的表面张力最低可达33.7mN/m,并且在浓度很低时仍具备较好的降低表面张力的能力。     

CMC系列高分子表面活性剂与原油 超低界面张力形成机理的研究

采用动态激光光散射及环境扫描电镜研究了羧甲基纤维素系列高分子表面活性剂与大庆原油形成超低界面张力的机理.结果表明,CMC系列高分子表面活性剂具有与低分子量表面活性剂相比拟的表/界面活性,其水溶液的表面张力可达28～35mN/m,界面张力达到10     

纤维素类高分子表面活性剂

纤维素类高分子表面活性剂因其具有原料丰富,可生物降解,使用安全性好等一般合成高分子表面生剂所难以具备的优点,目前正引起人们的广泛关注。本文综述了近２０年来其主要研究进展,内容涉及含长链烷基,含碳氟基团和含双亲链段３类纤维素类表面活性剂。     

Emulsion polymerization of styrene and methyl methacrylate using a hydrophobically modified inulin and comparison with other surfactants

The use of a new class of graft polymer surfactants, based on inulin, in emulsion polymerization of poly(methyl methacrylate) (PMMA) and polystyrene (PS) particles is described. PS and PMMA were synthesized by emulsion polymerization, and stable particles with a high monomer content (50 wt %) were obtained with a very small amount of polymeric surfactant ([surfactant]/[monomer] = 0.0033). The latex dispersions were characterized by dynamic light scattering and by transmission electron microscopy to obtain the average particle size and the polydispersity index, and the stability was determined by turbidimetry measurements and expressed in terms of critical coagulation concentration. The last section gives a comparison of PMMA particles prepared by emulsion polymerization using classical surfactants from different types as emulsifiers with that obtained using the copolymer surfactant. It shows the superiority of INUTEC SP1 as it is the only one that allows stable particles at 20 wt % monomer content, with a smaller ratio [surfactant]/[monomer] = 0.002.     

Macromolecular surfactants for miniemulsion polymerization

The use of polymeric surfactants as stabilizers in miniemulsion polymerization was reviewed. The structural characteristics of reported polymeric surfactants were detailed and compared. The concept of multi-functional polymeric surfactants was evidenced. The specificities brought by polymeric surfactants in the process of miniemulsion polymerization in comparison to molecular surfactants were analysed for the stability of the initial monomer emulsion, polymerization kinetics and characteristics of the obtained latexes. The contribution of polymeric surfactants to the control of the characteristics of the obtained nanoparticles was detailed with regard to the nature of the core material and to the surface coverage. Polymeric surfactants can be seen as powerful tools for the design of original nanoparticles. On the basis of the available data, possible research topics are suggested.     

Emulsion stability and potassium leakage in emulsion liquid membrane systems

Potassium leakage was studied in liquid membrane systems containing various emulsifiers and compared with emulsion, stability in the storage test. The effects of various parameters upon emulsion stability and the leakage of standard traces are discussed. The transfer of cations can be caused by emulsion breaking, by transport with the specific carrier and/or with surfactants used as emulsifiers. The latter case becomes especially important when hydrophilic surfactants, e.g. ones containing polyoxyethylene chains, are present in liquid membranes. In systems containing hydrophobic emulsifiers the transfer of potassium is relatively low. In each case considered the effect of emulsifiers upon the transfer of the standard tracer should be checked prior to using the leakage test to characterize emulsion stability.     

Synthesis of micron-sized polymeric particles in soap-free emulsion polymerization using oil-soluble initiators and electrolytes

Soap-free emulsion polymerization of styrene using oil-soluble initiators and electrolytes was investigated to synthesize micron-sized polystyrene particles. It was clear that an oil-soluble initiator, such as AIBN, worked like a water-soluble initiator in soap-free emulsion polymerization of styrene to prepare monodispersed particles with negative charges, probably because of the polarization of the electron-attractive functional groups decomposed from the initiators and the pi electron cloud of benzene in a styrene monomer. The addition of an electrolyte enabled secondary particles to effectively promote hetero-coagulation for particle growth by reduction of an electrical double layer and prevention of self-growth. Changing the concentration and type of electrolyte enabled us to control the size up to 12 μm in soap-free emulsion polymerization of styrene using AIBN. Conventionally, organic solvents and surfactants have been used to prepare micron-sized polymeric particles, but this method enabled the synthesis of micron-sized polymeric particles in water using electrolytes without surfactants.     

Imidazoline derivatives as promising cationic emulsifiers for styrene heterophase polymerization

The colloidochemical properties of new cationic surfactants synthesized from fatty acids of palm oil and diethylenetriamine are first studied. It is found that, at solution pH below 6.0, the examined surfactants exist mainly as salts formed from protonated surfactant molecules and residues of strong acids, e.g., hydrochloric acid. In the pH range above 7.0, the protonated and nonprotonated forms of the surfactants are at equilibrium, which shifts to the nonprotonated form with an increase in pH. The analysis of interfacial tension isotherms shows that the minimum values of the interfacial tension are achieved at pH 7.0 when the concentrations of the protonated and nonprotonated forms of surfactant molecules are equal. New cationic surfactants are used as emulsifiers in emulsion polymerization of styrene. It is found that stable polystyrene latexes with narrow particle size distributions and high positive ζ potentials (as high as +68.4 mV) can be obtained at styrene concentration in an initial emulsion of 25 vol % and surfactant concentration in an aqueous phase of 2 wt %. A hydrogen peroxide-iron(II) salt redox system is used as an initiator of polymerization at component concentrations equal to 5 and 0.05 wt % of the monomer, respectively.     

Surfactant characteristics of polystyrene/poly(ethylene oxide) macromonomers in aqueous solution and on polystyrene latex particles: Two‐step emulsion polymerizations

Macromonomers were synthesized by anionic “living” polymerization. They comprised a poly(ethylene oxide) hydrophilic block and a hydrophobic block or sequence terminated with an unsaturation. The surface activity properties of these materials (critical micelle concentration and parking area) were determined, and the values were compared and discussed in terms of the molecular structure of these new surfactants. Some of the macromonomers were employed as emulsifiers in two‐step emulsion polymerizations. The data obtained were discussed while taking into account the different chemical structures of the macromonomers and the efficiency of these species as emulsifiers in the polymerization recipes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2767–2776, 2001     

Stability of Emulsion Polymerization of New Fluorinated Acrylate Emulsion and Its Characterization

The new fluorinated acrylate emulsion was synthesized by using the intermediate perfluorous nonene and 2-hydroxyethyl methacrylate as the staring reactants via semi-continuous seeded emulsion polymerization. The structures, glass transition temperature, thermal property and water repellency of the fluorinated acrylate emulsion were characterized with FTIR, differential scanning calorimetry, thermal analysis, and contact angle meter. Influences of many factors such as the theoretical solid content, the temperature of the emulsion polymerization on the stability of the emulsion polymerization, the added amount of emulsifiers and the added amount of the initiator were studied. Results show that the stability of the emulsion polymerization is fairly good when the theoretical solid content is below 30% and the reaction temperature is 80°C and the added amount of emulsifiers and the initiator are 6.0–8.0% and 2.0% respectively. In comparison with the acylate emulsion, the thermal stability of the fluorinated acrylate emulsion is decreased but the water repellency of the fluorinated acrylate emulsion is greatly increased.     

Emulsion polymerization of acrylonitrile. Part I. Role and effect of emulsifiers in the emulsion polymerization of acrylonitrile

The role in and effects on the emulsion polymerization of acrylonitrile (AN) of three different groups of emulsifiers, i.e., low molecular emulsfiers, well-known water-soluble polymers, and new water-soluble polymers containing a sulfonate group have been investigated by a dilatometry and electron microscopy. The major part of this paper concentrates on the study of the relation between the properties of the third group of emulsifiers and emulsion polymerization characteristics of AN such as rate, degree of polymerization, diameter and number of particles, and the degree of dispersion, by adding copolymers of AN and sodium p-styrenesulfonate (SSS) having various compositions. In the emulsion polymerization of AN, the hydrophobic portion of the emulsifier seems to act as a kind of nucleus around which polymer molecules precipitate and particle formation may occur, and the hydrophilic portion stabilizes the polymer particles thus formed. As the number of particles and the degree of dispersion increases, the total surface of the particles increases, which may raise the overall rate of polymerization due mainly to an increased polymerization on the surface of the polymer particles. The well-known emulsifiers may be classified by the properties and ratio of the nucleus portion and the stabilizing portion. The unusual effect of emulsifiers on the degree of polymerization may be explained by a chain-transfer mechanism.     

Self-assembly and emulsification of poly{[styrene-alt-maleic acid]-co-[styrene-alt-(N-3,4-dihydroxyphenylethyl-maleamic acid)]}

Self-assembled polymeric micelles can be used as efficient particulate emulsifiers. To explore the relationship between the structure and the oil-water interfacial behavior of the micelle emulsifiers, a new type of amphiphilic random copolymer, poly{(styrene-alt-maleic acid)-co-[styrene-alt-(N-3,4-dihydroxyphenylethyl-maleamic acid)]} (SMA-Dopa), was synthesized, self-assembled into micelles, and used as emulsifiers. SMA-Dopa was synthesized via an aminolysis reaction between dopamine and commercial alternating copolymer poly(styrene-alt-maleic anhydride) (SMA). Dopamine moiety facilitated the self-assembly of the SMA-Dopa in selective-solvent into stable micelles, and increased the adsorption of the SMA-Dopa at the oil-water interface. Additionally, the structural transition of the self-assembled SMA-Dopa52 micelles in response to pH and salinity changes were confirmed by means of TEM, AFM, DLS, aqueous electrophoresis techniques, potentiometric titration, and pyrene fluorescence probe methods. Micelles shrunk with increasing salinity, and flocculation of the shrunken primary micelles occurred at salt concentration exceeding 0.1 M. The micelles swelled with increasing pH, and the disassociation of the SMA-Dopa52 micelles occurred at pH above approximately 6.5. The structure of the micelles plays a crucial role in the oil-water interfacial performance. Micelles with various structures were used as emulsifiers to adsorb at the styrene-water and toluene-water interfaces. The emulsifying characteristics demonstrated that self-assembled SMA-Dopa52 micelles with moderately swollen structure (at 2 < pH < 6) combine the advantages of the solid particulate emulsifiers and polymeric surfactants, possessing excellent emulsifying efficiency and good emulsion stability. Moreover, the emulsifying performance of the SMA-Dopa52 micelles could be enhanced by the addition of salt.