超浓乳液聚合体系稳定性的研究

介绍了超浓乳液及其制备方法、讨论了超浓乳液形成的条件,指出了不同单体体系的超浓乳液聚合的最佳稳定性条件。     

浓乳液聚合制备优先脱醇渗透蒸发分离膜

提出了一种以浓乳液聚合直接浇注制备新型有机硅类渗透蒸发分离膜的新方法。考察了乙醇浓度、分离时间与渗透蒸发分离性能之间的关系,表征了有机硅浓乳液聚合过程中的乳胶粒子形态与成膜后粒子堆砌的微观结构。结果表明,利用膜中乳胶粒子间微通道的极性效应可以有效地分离醇/水混合物中的醇,且优先脱醇效果明显,分离性能良好。在乙醇/水混合物的渗透蒸发膜分离实验中,其渗透通量为4.7～165g·m-2·h-1,分离因子为1.0～11.3,分离选择性最好时的料液中乙醇的质量分数为33.41%。     

阳离子聚丙烯酰胺微球浓乳液制备及粒径演化

浓乳液聚合产品稳定性好,颗粒尺寸更接近地层孔隙尺寸,在油田开发中具有较大的应用价值。基于微乳液制备了一系列甲基丙烯酰氧乙基三甲基氯化铵和丙烯酰胺的浓乳液,通过电导率测试、流变性分析、显微镜观察,研究了聚合前后浓乳液结构、粒径分布及稳定性。结果表明浓乳液的黏度及屈服应力,随着水相单体浓度（C_M）增加而降低,随着油相中表面活性剂含量（m_S）增加先升高后降低,乳液稳定性有相同趋势;浓乳液在C_M>40%及m_S=2.5 g时的失稳,原因分别是渗滤作用和高黏度下乳化不充分;聚合前液滴粒径分布在1～30 mm,聚合后微球粒径在0.4～5 mm,且粒径分布由聚合前双峰变为聚合后单峰,这一现象可以由Kolmogoro-Hinze的乳化理论解释,并由微球乳液的黏度增加至原始浓乳液的10倍证实。     

超浓乳液及其应用

介绍了超浓乳液的制备方法、形成条件以及在各领域的应用.讨论了超浓乳液的相行为与稳定性及各自的影响因素,比较了超浓乳液聚合与本体聚合、传统乳液聚合的区别.超浓乳液聚合存在聚合物分子量大,聚合速率快,乳胶粒子粒径可控等优点.     

室温可自成膜中空微粒乳液的制备

采用羧基单体进行多阶段的种子乳液聚合,制备了内核为带羧基的聚合物、最外层为易成膜的低玻璃化温度聚合物、中间为轻度交联中间隔离层的多层核壳结构乳胶粒,最后通过碱处理制成了具有室温成膜性的中空结构聚合物微粒。研究表明,在反应前期以十二烷基苯磺酸钠为乳化剂,包壳阶段同时加入OP-10可有效控制乳胶粒结构形态,同时提高聚合物乳液的电解质稳定性;以甲基丙烯酸为羧基单体,其用量为核单体总量的30%(质量分数)时,聚合物微粒中空直径较大且微粒结构规整;碱处理温度以100℃为宜。在优化的工艺下,制得的室温可成膜中空聚合物微粒外径约500 nm,中空直径约300 nm。     

Polystyrene latex particles bearing primary amine groups via soap‐free emulsion polymerization

Polystyrene latexes were prepared in the presence of an amino‐containing functional comonomer, N‐(3‐aminopropyl)methacrylamide hydrochloride (APMH), via soap‐free batch emulsion polymerization initiated by the cationic initiator 2,2′‐azobis(2‐amidinopropane) dihydrochloride. These latexes were characterized by studying the influence of the ionic comonomers on the polymerization kinetics, particle size, surface charge density and colloidal properties. The synthesized latexes were monodisperse with a final size between 100 and 600 nm depending on the APMH concentration. The initial polymerization rate and the particle number increased in accordance with the Smith–Ewart theory for soap‐free styrene emulsion polymerization with a hydrophilic functional comonomer. The final functionalization rate of the particles has been particularly studied with the intention of fitting the prepared latexes to be used in the immobilization of biological molecules for biological sample preparation and diagnostic applications. © 2020 Society of Chemical Industry     

Preparation of poly(methyl methacrylate)/titanium oxide composite particles via in‐situ emulsion polymerization

Poly(methyl methacrylate) (PMMA)/Titanium oxide (TiO₂) composite particles were prepared via in‐situ emulsion polymerization of MMA in the presence of TiO₂ particles. Before polymerization, the TiO₂ particles was modified by the silane coupling agent, which is crucial to ensure that PMMA reacts with TiO₂ via covalent bond bindings. The structure of the obtained PMMA/TiO₂ composite particles was characterized using Fourier transform infrared spectra (FTIR) and thermogravimetric analysis (TGA). The results indicate that there are covalent bond bindings between PMMA macromolecules and TiO₂ particles. Based on these facts, several factors affecting the resulting PMMA/TiO₂ composite system, such as the type of coupling agents, the mass ratio of the MMA to the modified TiO₂, the emulsifier concentration, and the initiator concentration, etc., were examined by the measurement of conversion of monomers, the gel content of polymers, the percentage of grafting, and the grafting efficiency, using gravity method or TGA method. As a result, the optimized recipe was achieved, and the percentage of grafting and the grafting efficiency could reach 216.86 and 96.64%, respectively. In addition, the obtained PMMA/TiO₂ composite particles were found to a stable colloidal dispersion in good solvent for PMMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4056–4063, 2006     

超浓乳液聚合的研究和应用

介绍超浓乳液聚合的概念、研究状况、特点以及超浓乳液的制备、稳定性的影响因素及其在新材料中的应用.     

Preparation and structure control of hollow polymer particles: Influence of seeded emulsion polymerization and alkalization treatment process

Hollow polymer latex particles containing a hydrophilic core were prepared by seeded emulsion polymerization with MAA/BA/MMA/St as comonomers, followed by stepwise alkalization treatment with ammonia. The size and morphology of composite latex particles was determined by TEM. The effects of the seeded emulsion polymerization conditions and alkalization treatment on the size and hollow structure of latex were investigated. The results showed that the optimum content of crosslinking agent in the shell polymers was about 0.5–1.0 wt %, emulsifier was about 0.8–1.1 wt %, and the core/shell weight ratio was 1/7. To obtain uniform hollow latex particles with large size, the starved feeding technique should be adopted in seeded emulsion polymerization, and the neutralization temperature should equal to the T_g of the shell polymer. Then, the obtained polymer particles under this condition had an excellent hollow structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

双相浓乳液聚合制备聚丙烯酸丁酯多面体粒子

用浓乳液双相聚合法制备了粒径均匀的聚丙烯酸丁酯多面体粒子.结果表明,由于分散相体积分数较高而造成的挤压,浓乳液形成多面体模板,分散相液滴聚合形成多面体粒子.连续相中的亲水聚合物隔层和粒子的适度交联保证了多面体粒子的独立性.     

Preparation and characterization of titanium dioxide core/polymer shell hybrid composite particles prepared by emulsion polymerization

Titanium dioxide inorganic core and polymer shell composite poly(methyl methacrylate‐co‐butylacrylate‐co‐methacrylic acid) [P(MMA‐co‐BA)‐MAA] particles were prepared by emulsion copolymerization. Fourier transform IR (FTIR) spectroscopy was used to measure the content of MAA composite particles. Dynamic light scattering (DLS) characterized the composite particle size and size distribution. The field emission SEM (FE‐SEM) results of the composite particles showed regular spherical shape and no bare TiO₂ was detected on the whole surface of the samples. The composite particles were produced, showing good spectral reflectance compared with bare TiO₂. TGA results indicated the encapsulation efficiency and estimated density of composite particles. Encapsulation efficiency was up to 78.9% and the density ranged from 1.76 to 1.94 g/cm³. Estimated density of the composite particles is suitable to 1.73 g/cm³, due to density matching with suspending media. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2970–2975, 2004     

Attapulgite@polymer particles with double‐layer polymer shell via soapless seeded emulsion polymerization

Attapulgite needle encapsulated with double‐layer polymer shell (ATP@DP) were prepared by the soapless seeded emulsion polymerization of the second monomer styrene in the dispersion of the attapulgite needle encapsulated with poly(methyl methacrylate) (ATP@PMMA), which was also conducted by the soapless seeded emulsion polymerization of the first monomer methyl methacrylate with the cetyltrimethylammonium bromide (CTAB) modified attapulgite needle (org‐ATP) as seeds. The different morphologies of ATP, ATP@PMMA particles, and ATP@DP particles were characterized by transmission electron microscopy, and the encapsulation mechanism was also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Modeling the emulsion polymerization of amino-functionalized latex particles

A mathematical model for a semicontinuous seeded cationic emulsion polymerization was developed. The model includes the most distinctive features of the copolymerization of a cationic hydrophilic monomer with a hydrophobic one, including polymerization of the hydrophilic monomer in the outer shell of polymer particles and in the aqueous phase, and the possibility of having radical concentration profiles in the polymer particles.The reactions were carried out by means of a semicontinuous seeded cationic emulsion polymerization under starved conditions for styrene, which was the main monomer employed.The model predicts the evolution of the fractional overall conversions, the thickness of the outer shell, the total surface charge density and the partial conversions for the semicontinuous seeded cationic emulsion polymerization of styrene and aminoethyl methacrylate hydrochloride. Furthermore, the model can distinguish between the surface charge density provided by the cationic monomer than that given by the cationic initiator. Therefore, this model can predict the best conditions to obtain well-defined latexes with specific amounts of surface amino and amidine groups useful for immunoassays.     

Preparation of planar and oblate particles from emulsion polymerization using polymerizable comb-like branched emulsifiers

This paper presents a method for preparation of planar polymeric microstructures by emulsion polymerization using polymerizable branched emulsifier. Planar, oblate and spherical particles can be prepared by changing the volume and functionality of the hydrophobic tail of the comb-like polymerizable emulsifier, together with altering the monomers. Emulsifiers with bulky tails favored the formation of planar microstructure. The polymerizable emulsifiers were immobilized on the latex particles. Hindered desorption of the emulsifier from the latex improved the latexes' stability and facilitate the formation of planar and oblate particles. The polymerization conversion also depends on the molecular characteristics of the emulsifiers and monomers.     

乳液聚合法聚丙烯酸树脂的制备研究

介绍了以丙烯酸、苯乙烯、丙烯酸丁酯、丙烯酸羟丙酯为单体,采用过硫酸铵作为引发剂,以非离子乳化剂聚氧乙烯醚(OP-10)和阴离子乳化剂十二烷基硫酸钠(SDS)作为复合乳化剂,经过乳液聚合,制得了一种水性涂料用缔合型增稠剂.考察了丙烯酸单体含量、乳化剂用量对乳液性能和增稠剂黏度的影响.优化了反应条件,反应过程和最终乳液都很...     

Preparation of highly open porous styrene/acrylonitrile and styrene/acrylonitrile/organoclay polymerized high internal phase emulsion (PolyHIPE) foams via emulsion templating

Highly open porous crosslinked styrene/ acrylonitrile (SAN) polymerized high internal phase emulsion (PolyHIPE) foams containing various amounts of acrylonitrile (AN) were prepared by the polymerization of the continuous organic phase of high internal phase emulsions with an 85 vol % aqueous internal phase. The mean diameter of voids varied in the range 12.4–19.8 μm. The void diameter increased up to 10% AN, but beyond this limit, the diameter decreased. To improve the mechanical properties of the copolymer foams, the organic phase of the emulsion containing 20% AN was reinforced with organomontmorillonites with different surface modifiers. The effects of the organoclay on the equilibrium torque value of the emulsifying systems, as an approximate characteristic of the emulsion viscosity, and on the morphology and mechanical properties of the resulting foam were investigated. Scanning electron micrographs exhibited an open‐cell polyHIPE structure for all of the SAN/organoclay polyHIPE foams. The incorporation of organoclays within the emulsion copolymer foam significantly decreased the mean size of voids and intercellular pores compared with those of the copolymer foam without reinforcement. In fact, the presence of organoclay may have acted as a cosurfactant to improve the performance of the nonionic surfactant in the concentrated emulsions. The X‐ray diffraction patterns and transmission electron micrographs showed an intercalated nanocomposite structure for the organoclay‐reinforced copolymer foams. On the other hand, the addition of a more hydrophilic organoclay, that is, 3 wt % Cloisite30B, to the concentrated emulsion decreased the Young's modulus and significantly improved the crush strength of the emulsion copolymer foam. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

无皂乳液聚合制备亚微米级单分散聚苯乙烯微球

采用无皂乳液聚合法制备了具有单分散性的亚微米级聚苯乙烯微球,考察了聚合体系pH值、单体及引发剂用量对聚合转化率、微球粒径及其分布的影响。结果表明,采用NaOH和NaHCO,复合溶液调节聚合体系pH值是控制聚合动力学、微球粒径及单分散性的有效手段,当其质量比为1：1时效果较好。随碱性复合溶液加入量的增加,最终转化率下降,微球粒径则由于复合溶液同时起到电解质的作用而存在极大值。随过硫酸钾(KPS)质量分数的增加,反应前期聚合转化率增大,但其用量过大,会导致体系pH值偏低,KPS过早消耗完毕,故反应后期最终转化率偏低;其用量过低,会影响粒径的单分散性。当KPS质量分数为单体的2％～3％时,聚合体系稳定性增加并改善了微球的单分散性,粒径趋小。单体用量的变化对聚合速率影响不大,随单体质量分数的提高,微球最终粒径增大,当单体质量分数过高,会影响微球的单分散性乃至体系失稳,一般以不超过10％为宜。     

Thin layer concentrated emulsion copolymerization of PUASi/Styrene/Methyl methacrylate

Stable concentrated emulsions of polymerizable polysiloxane‐containing polyurethane (PUASi)/Styrene (St)/Methyl methacrylate (MMA) were prepared using sodium dodecyl sulphate (SDS)/nonyl polyoxyethylene ether (OS15)/polyvinyl alcohol (PVA) as composite surfactant and azobisisobutyronitrile (AIBN) as initiator. A novel polymerization method, thin layer polymerization was used to carry out the concentrated emulsion copolymerization at 55°C. The effects of TDI/PPG molar ratio, surfactant concentration, different kinds of surfactants, and temperature on polymerization stability were studied. The effects of the thickness of the thin layer, the outside temperature of the reactor, as well as polymerization environment on the volatilization rate of water, and monomer in the system were investigated. The conversion‐time relationships of the thin layer polymerization and the tube polymerization, as well as the effect of polymerization environment on the polymerization rate were also investigated. The morphology of latex particles was determined with transmission electron microscope (TEM). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Monodispersed composite particles prepared via emulsifier‐free emulsion polymerization using waterborne polyurethane as microreactors

Monodispersed polystyrene particles in submicrometer size were intriguingly prepared through emulsifier‐free batch‐seeded emulsion polymerization using nonmonodispersed waterborne polyurethane (WBPU) beads as microreactors. Different feed ratios of styrene (St)/WBPU for the preparation of composite particles were investigated, and the size–growth course was experimentally followed. The morphology and dispersity of the particles were characterized by scanning electron microscopy together with dynamic laser scattering particle size analyzer. Their inside structure was further characterized by transmission electron microscopy with ultramicrotomy combined with X‐ray photoelectron spectroscopy for the composite particles' surface analysis. The probable grafting polymerization of St from WBPU was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance instrument. The obtained composite particles were again employed as the seeds in the emulsion copolymerization of methyl methacrylate. As a result, the formed multilayered composite particles with reverse core–shell structure were also monodispersed and spherical. The mechanism of the formation of the monodispersed particles was proposed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40985.     

High solids content emulsions. III. Synthesis of concentrated latices by classic emulsion polymerization

Two different methods of producing bi‐ and trimodal latices of a mixture of methyl methacrylate, butyl acrylate, and small amounts of acrylic acid were tested. It is shown that a combination of concentrating blends of seed particles by semibatch reaction, followed by a nucleation of small particles plus a second semibatch phase allowed us to obtain stable latices with solids contents over 65% and viscosities of below 2500 mPa s^?1 with little coagulum formation. The key parameter in determining latex stability, coagulum formation, and viscosity appears to be the the particle size distribution, and especially its modification attributed to secondary nucleation. Because it is not possible to eliminate water‐soluble monomers from the polymerization recipe, secondary (homogeneous) nucleation must be minimized by careful addition of the free‐radical initiator and choice of monomer feed flow rates. The nucleation of the third population in the trimodal latices is best accomplished with a mixed surfactant system because renucleation by anionic surfactant alone leads to detrimental changes in the particle size distribution (PSD) resulting from excessive flocculation of particles. In addition, it was found that the viscosity of the final products was not sensitive to small changes in the ionic strength of the latex, although neutralization to a pH of 6 effectively doubles the final latex viscosity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1916–1934, 2002; DOI 10.1002/app.10513