Monodisperse ultrafine polystyrene nanoparticles prepared by a semicontinuous microemulsion polymerization

Monodisperse ultrafine polystyrene nanoparticles have been successfully prepared under low levels of surfactant through a novel semicontinuous microemulsion polymerization, in which the first part of monomer (St₁) is added dropwise while the subsequent supply to the polymerizing system is delivered in one potion. Polystyrene nanoparticles with number‐average diameter of 17.4 nm and polydispersity index of 1.06 were obtained using low level of surfactant/monomer weight ratio of 0.20. Influencing of parameters including amount of St₁, solid content, initiator, reaction temperature, and cosurfactant on the resultant particle size and size distribution were investigated. The mechanism of nucleation and particle growth was discussed as well. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4522–4528, 2008     

Micron-sized monodispersed polymer particles produced by seeded polymerization for the dispersion of high swelling of polymer particles with a large amount of monomer

 Micron-sized monodispersed polystyrene (PS)/poly(n-butyl methacrylate) composite particles were produced as follows. First, 1.77 μm-sized monodispersed PS seed particles produced by dispersion polymerization were dispersed in ethanol/water (1/2, w/w) medium dissolving poly(vinyl alcohol) as a stabilizer. n-Butyl methacrylate (BMA) monomer dissolving benzoyl peroxide initiator was emulsified in ethanol/water (1/2, w/w) solution of sodium dodecyl sulfate as emulsifier with ultrasonic homogenizer, and the BMA monomer emulsion was mixed with the PS seed emulsion. The PS seed particles absorbed with a large amount of BMA (about 150 times weight of the seed particles) for 2 h to about 10 μm in diameter while keeping good monodispersity and BMA droplets disappeared finally. The seeded polymerization was carried out at 70 °C after a certain amount of water was added to depress the redissolving of BMA from the swollen particles into the medium by raising from room temperature to the polymerzation temperature. Received: 21 February 1996 Accepted: 4 September 1996     

Effects of stirring prior to starting emulsion polymerization of styrene with nonionic emulsifier on particle formation and its incorporation

Emulsion polymerization of styrene with a nonionic emulsifier (polyoxyethylene nonylphenyl ether, E911) and potassium persulfate as initiator was carried out at different stirring rates (240–500 rpm) at 70 °C, which was started by the addition of initiator after stirring for 100 min at 70 °C. Resulting polystyrene (PS) particles at 240 rpm were 70-nm-sized, spherical particles and incorporated only 5 wt.% of total E911. On the other hand, particles at 500 rpm were 1-μm-sized, nonspherical particles, which were formed by coagulation of small particles, and incorporated above 70 wt.% of E911 in the inside. Before starting emulsion polymerization, E911 and styrene, respectively, transferred from an aqueous phase to a styrene phase and from the styrene phase to the aqueous phase (water and micelles) faster at 500 rpm than 240 rpm. At 240 rpm, there were a lot of almost empty micelles (ca. 5 nm) in the aqueous phase, on the other hand at 500 rpm, 70 wt.% of total E911 transferred to the styrene phase and the micelles were swollen with much monomer (ca. 40 nm) even if the number was smaller. Stirring prior to starting the emulsion polymerization greatly affected partitionings of monomer to the aqueous phase and the nonionic emulsifier to the styrene phase, resulting in the differences in the particle formation and the incorporation of the nonionic emulsifier inside PS particles.     

Model filled polymers. VIII. Synthesis of crosslinked polymeric beads by seed polymerization

Monodisperse crosslinked polystyrene (PS) and polymethacrylate (PMA) beads of sizes greater than 1 μm in diameter are prepared by particle nucleation onto pre-existing polymer seeds in a multistage emulsion polymerization, in the absence of emulsifier. An adequate seed number concentration, which decreases with increasing seed size, is necessary to achieve monodisperse beads. Monodisperse multicomposition beads are prepared by polymerizing styrene onto PMA seeds, but not by polymerizing methyl methacrylate onto PS seeds. Phase separation in growing seed particles or surface polymerization following free radical capture may lead to the formation of asymmetric shaped particles.     

Ultrasonically induced microemulsion polymerization of styrene

In this paper, ultrasonically induced microemulsion polymerization of styrene was successfully performed, possessing many merits such as high polymerization rate, the formation of small latex particles with a narrow size distribution, the absence of initiator and relatively low surfactant concentration. The monomer conversion reached 70% in 1 h, and the average diameter of polystyrene (PS) latex was about 30 nm which could be prepared with 3% surfactant (sodium dodecyl sulfate, SDS) concentration. The molecular weight of PS was around 10⁶ and the poly-distribution index was 1.06, indicating a very narrow distribution. Several influencing factors were investigated in detail, showing that ultrasonically induced microemulsion polymerization is a new route to prepare PS nanoparticles.     

Synthesis of large-sized monodisperse polystyrene microspheres by dispersion polymerization with dropwise monomer feeding procedure

Highly monodisperse polystyrene (PS) microspheres in the size range of 3.75–7.09 μm were synthesized by dispersion polymerization with dropwise monomer feeding procedure. The morphology, size, and particle size distribution (PSD) of the PS microspheres obtained by different monomer feeding modes, including batch polymerization and various feeding rates, were investigated. The PSD of particles showed a close dependence on feeding rate. The PS microspheres with low coefficient of variation (CV) values all less than 4.8% obtained by the optimum feeding rates revealed better uniformity than those by batch polymerization (CV values all more than 8.2%). According to the time courses of monomer conversion and particle numbers, the effects of monomer feeding modes on the polymerization reaction of the large-sized PS microspheres were clarified. It is found that the dropwise monomer feeding procedure is promising for the synthesis of large-sized monodisperse PS particles in 3.75–7.09 μm.     

Facile preparation method of SiO2/PS/TiO2 multilayer core-shell hybrid microspheres

Organic-inorganic hybrid particles have many potential applications, but almost all of this research was focused on the hybrid particles containing one kind of inorganic nanoparticles. This paper presented a facile preparation method for SiO2/PS/TiO2 multilayer core-shell hybrid microspheres. In this approach, positively charged SiO2/PS core-shell hybrid particles were first synthesized by miniemulsion polymerization using cationic initiator and emulsifier. These positively charged SiO2/PS hybrid particles were mixed with tetra-n-butyl titanate for sol-gel reaction to directly form SiO2/PS/TiO2 multilayer core-shell hybrid microspheres. Some influencing parameters such as surfactant concentration, tetra-n-butyl titanate amount, and glacial acetic acid amount were investigated. TEM, TGA, and EDX analyses indicated that titania layers were successfully coated onto the surfaces of hybrid microspheres.     

无乳化剂乳液聚合法合成单分散大粒径高分子微球的研究

无乳化剂乳液聚合法合成单分散大粒径高分子微球的研究朱世雄杜金环金熹高陈柳生（中国科学院化学研究所北京１０００８０）关键词无乳化剂乳液聚合，单分散，均相成核，低聚物胶束微米级大粒径单分散高分子微球在标准计量、情报信息、分析化学等许多领域都有广泛的...     

单分散、大粒径聚苯乙烯微球的制备

以聚乙烯基吡咯烷酮为分散剂、偶氮二异丁腈为引发剂、醇／水混合物为分散介质进行了苯乙烯的分散聚合，讨论了初始单体浓度、分散剂用量、引发剂浓度、分散介质组成和反应温度等反应条件对所得聚合物颗粒直径和直径分布的影响．通过大量的试验，筛选出了较为理想的分散聚合的条件及配方，制备出了粒径为４８μｍ的单分散聚苯乙烯微球．然后，以分散聚合所制得的聚合物颗粒为种子，用动力学溶胀法制成了粒径增大近四倍的单分散、大粒径聚苯乙烯微球，并讨论了滴水速度和补加分散剂对溶胀的影响     

Kinetics and mechanisms of emulsion polymerization of vinylidene chloride. I. Effects of operating variables on the rate of polymerization and the number of polymer particles produced

Emulsion polymerization of vinylidene chloride was carried out at 50°C using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator, respectively. Contrary to the results so far reported, the stirring rate did not affect the progress of the polymerization and such an abnormal kinetic behavior as the rate of polymerization suddenly drops in the course of polymerization was not observed. The number of polymer particles produced was proportional to the 0.7 power of the concentration of emulsifier forming micelles and to the 0.3 power of the initial initiator concentration, respectively, and was independent of the initial monomer concentration. The rate of polymerization was in proportion to the 0.3 power of the concentration of emulsifier forming micelles, to the 0.5 power of the initial initiator concentration, to the 0.2 power of the initial monomer concentration, and to the 0.45 power of the number of polymer particles, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1919–1928, 1998     

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。     

聚硅氧烷/丙烯酸酯核/壳复合胶乳的粒径分布与成核机理

通过种子乳液法合成出具有高有机硅含量核 壳结构的聚硅氧烷 丙烯酸酯复合粒子 .研究了聚合方法、乳化剂浓度、引发剂浓度、单体滴加速度等工艺条件对复合乳液粒径尺寸、分布与形态的影响 ,并对复合乳液的成核机理进行了探讨 .研究表明 ,乳化剂浓度对乳液粒子的粒径分布和形态、结构有显著影响 ,引发剂浓度增加将使粒子粒径减小 ;相对一次投料法 ,种子乳液法生成的粒子分布窄 ,具有明显核壳结构 ,通过壳层单体滴加速度可以控制粒子的粒径尺寸和分布 ;而壳层丙烯酸酯聚合物主要是在聚硅氧烷种子表面的“过渡层”聚合、富集而成 .     

Production of micron-sized monodispersed polymer particles by seeded polymerization for the dispersion of highly monomer-swollen particles prepared with submicron-sized polymer seed particles utilizing the dynamic swelling method

For the purpose of extending the size range of polymer seed particles used in “dynamic swelling method” (DSM), first it was verified theoretically that the submicron-sized polymer particles produced by emulsion polymerization can also absorb a large amount of monomer by DSM in both equilibrium and kinetic control states. Next, on the basis of the theoretical results, experimentally about 2.6 μm-sized styrene-swollen polystyrene (PS) particles were prepared utilizing DSM in the presence of 0.64 μm-sized monodispersed PS seed particles produced by emulsifier-free emulsion polymerization. Moreover, 2.5 μm-sized monodispersed PS particles were produced by the addition of cupric chloride as a water-soluble inhibitor to depress the by-production of submicron-sized PS particles in the seeded polymerization at 30°C with 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) initiator. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2513–2519, 1998     

Kinetics and mechanisms of emulsion polymerization initiated by oil-soluble initiators. IV. Kinetic modeling of unseeded emulsion polymerization of styrene initiated by 2,2′-azobisisobutyronitrile

To explain the kinetic features of particle formation and growth in unseeded emulsion polymerization initiated by oil-soluble initiators, a mathematical kinetic model is proposed, based on the assumption that when initiator radicals or monomer radicals in the water phase enter monomer-solubilized emulsifier micelles, initiate polymerization, and propagate to a chain length which is long enough not to desorb from the micelles, the micelles are regarded to be transformed into polymer particles. It is demonstrated by comparing the experimental results obtained in the emulsion polymerization of styrene initiated by the oil-soluble initiator, 2,2'-azobisisobutyronitrile, with sodium lauryl sulfate as emulsifier that the proposed kinetic model satisfactorily explains the kinetic features such as the effects of initial emulsifier, initiator, and monomer concentrations on both the number of polymer particles produced and the monomer conversion versus time histories. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of polychloromethylstyrene nanoparticles of narrow size distribution by emulsion and miniemulsion polymerization processes

Polychloromethylstyrene nanoparticles of sizes from 12.0 ± 2.3 to 229.6 ± 65 nm were prepared by the emulsion and miniemulsion polymerization of chloromethylstyrene in an aqueous continuous phase in the presence of potassium persulfate as initiator, sodium octylbenzenesulfonate as surfactant, and hexadecane as costabilizer for the miniemulsion polymerization process only. The influence of various polymerization parameters (e.g., concentration of the monomer, initiator, the crosslinker monomer, and the surfactant) on the properties of the particles (e.g., size, size distribution, and yield) has been elucidated. The polychloromethylstyrene nanoparticles formed via the emulsion polymerization mechanism possess smaller diameter and size distribution than those formed under similar conditions via the miniemulsion polymerization mechanism. Other differences between these two polymerization mechanisms have also been elucidated. For future study, we wish to use these nanoparticles for the covalent immobilization of bioactive reagents such as proteins to the surface of these nanoparticles for various biomedical applications.     

PS/CaCO_3复合纳米粒子及PS纳米空心球的制备研究

以CaCO3为核,采用原位乳液聚合法合成了表面接枝型和交联型PS/CaCO3复合纳米粒子,然后用稀盐酸刻蚀,得到PS纳米空心球.考察了乳化剂类型和用量、引发剂加入方式、加料间隔对乳液稳定性以及复合粒子收率、PS接枝效率的影响,并采用TGA、FT-IR和TEM等手段对刻蚀前后粒子的组成及形貌进行了表征.结果表明,阳离子型乳化剂更有利于乳液体系的稳定性;CTAB用量为3.7%~5.5%时,可获得较高的收率和接枝效率,随CTAB用量增加,粒径减小,分布变宽;AIBN应避免和单体、CaCO3粒子一起超声波处理,否则会导致不可逆凝聚;随着加料间隔延长,收率和接枝效率下降,一步加料法可获得具有高收率和高接枝效率(或交联程度)的复合粒子;经刻蚀,两种类型的复合粒子均可以制得空心粒子,但经过交联的聚合物外壳具有更好的尺寸和形状稳定性,刻蚀后仍然能保持球状的外形.     

St/交联剂乳液共聚包覆硬脂酸改性碳酸钙颗粒的研究

在硬脂酸改性的纳米碳酸钙存在下,通过苯乙烯(St)与多乙烯基单体的乳液共聚合,制备了以纳米碳酸钙为核,以交联聚苯乙烯(PS)为壳的交联型PS/碳酸钙复合纳米粒子.研究了多乙烯基单体的种类和用量以及碳酸钙的用量对聚合反应以及包覆的影响.结果表明,多乙烯基单体以及碳酸钙的引入会使聚合反应速率有不同程度的降低;使用1%~5%的TMPTMA或DVB,可实现PS对碳酸钙颗粒的牢固包覆,不可抽提的PS达94%以上;当碳酸钙用量改变时,需要适当调整乳化剂和多乙烯基单体的用量;IR和TGA的结果表明,随着碳酸钙用量增加,产物中的碳酸钙含量也相应增加;TEM照片和计算结果显示,当碳酸钙用量为14.8%时,绝大部分碳酸钙颗粒被包覆,且基本上每个乳胶粒中包覆一个碳酸钙颗粒,复合粒子具有清晰的核壳结构,壳层厚度约为10 nm,而当碳酸钙用量增加到29.3%和58.7%时,壳层厚度减小,并且出现较多裸露的碳酸钙颗粒.     

超细荧光聚合物纳米微球的制备

合成了具有较高荧光量子产率(0.69)和良好光稳定性的可聚合荧光染料单体,该荧光染料的光稳定性高于商品化的染料罗丹明B。 通过氧化还原引发剂引发乳液聚合制备了超细荧光聚合物纳米微球,将染料分子共价连接在聚合物链上。 使用非离子表面活性剂Triton X-100作为乳化剂、甲基丙烯酸甲酯(MMA)作为单体和助乳化剂,制备的超细纳米微球平均粒径为22 nm,而不加MMA时制备出的纳米微球平均粒径在150 nm左右。 由于微球表面带有苄氯基团,为进一步的微球功能化提供了途径。     

Radiation-induced emulsion polymerization of ethylene. II. Effect of potassium myristate concentration and dose rate on the rate of polymerization in connection with polymer properties,kinetics, and mechanism

Radiation-induced emulsion polymerization of ethylene with potassium myristate as an emulsifier was studied in connection with the kinetics and the mechanism. The molecular weight of polymer was relatively low, of the order of 10³, when a sufficient amount of emulsifier was used. However, polyethylene gel was produced in the absence of a sufficient amount of emulsifier. The rate of polymerization was proportional to the 0.5 power of dose rate and increased slightly with increasing emulsifier concentration. The rate of seeded polymerization followed a similar trend to that for conventional polymerization. Kinetic analysis of these results suggests that the escape of radicals produced by chain transfer of propagating radical with the emulsifier and the monomer from polymer particles into the aqueous phase plays an important part in the rate of polymerization. The melting temperature and the crystallinity of the polymer significantly decreased with increasing polymerization temperature in the range 40–60°C.     

Preparation of multihollow polystyrene particles by seeded emulsion polymerization using seed particles with incorporated nonionic emulsifier: effect of temperature

Seeded emulsion polymerizations of styrene using polystyrene (PS) seed particles with incorporated nonionic emulsifier were carried out at 40 and 70 °C to investigate the influence of temperature during the polymerization process including the swelling step of the seed particles with monomer on the formation of multihollow PS particles. An increase in the temperature during the polymerization process caused an increase in the rate of coalescence (i.e., the degree of coalescence at any given time) of the small water domains in the inside. After the coalescence proceeded excessively, the water domains were eventually discharged from the particles to the medium, resulting in nonhollow particles. The results show that it is important for the preparation of the multihollow PS particles to control the coalescence of a lot of small water domains inside the seed particles with the incorporated nonionic emulsifier, and strongly support the formation mechanism previously proposed. Part CCCXX of the series “Studies on Suspension and Emulsion”.