种子溶胀法制备单分散交联聚苯乙烯微球

采用分散聚合法制备了聚苯乙烯(PS),并以此作为种子,与溶胀剂和单体、交联剂的混合物经二步溶胀聚合法,制备了单分散交联PS微球.讨论了溶胀剂用量、交联剂用量和单体用量对溶胀微球粒径和粒度分布的影响,以及交联剂用量对溶胀微球形貌的影响.结果表明,当溶胀剂的用量为3 g,交联剂为1 g,单体用量为7 g时可制得平均粒径为6.84 μm且单分散性较好的交联PS微球.     

两步法制备交联聚苯乙烯微球研究

采用两步法制备出了粒径均一,球形度好的3μm交联聚苯乙烯微球。通过对两种条件下溶胀所得微球进行比较可知加入溶胀剂时制备出的微球球形度更好,表面更光滑,粒径分布范围更窄。较佳的制备条件为:聚苯乙烯单体的用量为种子微球的2.5~3.5倍,溶胀剂用量为种子微球的1~2倍,交联剂的用量为苯乙烯用量的5%~12%。     

种子溶胀法制备聚甲基丙烯酸酯类微球

以分散聚合法制得的单分散聚苯乙烯微球为种球,采用改进的两步种子溶胀法制备了粒度均一、高交联、多孔的聚甲基丙烯酸缩水甘油酯-乙二醇二甲基丙烯酸酯微球,并系统探索了稳定剂种类和浓度、活化剂用量、溶胀倍数、致孔剂的种类及比例对微球形态和粒径分布的影响,同时用光学显微镜、扫描电镜、红外光谱及高效液相色谱对微球进行了表征。结果表明,以2μm和4μm的聚苯乙烯微球为种球,当活化剂与种球质量比为4,溶胀倍数为20~40倍,致孔剂为体积比为6∶4的环己醇和甲苯混合溶剂,以质量分数0.2%的羟丙甲基纤维素(以整个体系质量计,下同)为稳定剂时可制得粒径5μm和10μm的单分散高交联多孔的聚甲基丙烯酸酯类微球。     

负载玫瑰香精多孔微球的制备及缓释性能研究

以分散聚合合成的单分散聚苯乙烯微球作为种子微球,采用两步种子溶胀法制备多孔聚苯乙烯-二乙烯苯微球,并吸附玫瑰香精制备了香精多孔微球。利用马尔文激光粒度仪、比表面积孔径分布测定仪(BET)、热重分析仪(TGA)、扫描电镜(SEM)对种子微球和多孔微球的粒径、比表面积和孔结构、缓释性能、表观形貌进行了分析表征。结果表明:种球的粒径随着分散介质中无水乙醇体积分数的增大而增加;随着溶胀剂邻苯二甲酸二丁酯(DBP)用量的增加,多孔微球的平均粒径变大,分布变宽;随着交联单体二乙烯苯(DVB)用量增加,多孔微球平均粒径减小,分布变窄;以甲苯为致孔剂制备的多孔微球单分散性最好。当V(DBP):m(种球)=3:1,V(DVB):V(苯乙烯)=4:0时,制备的多孔微球的平均粒径约为4μm。以此多孔微球负载玫瑰香精,可以减缓香精的释放速率,提高起始分解温度,实现对香精的缓释。     

致孔剂用量对苯乙烯悬浮聚合微球粒径和密度的影响

以苯乙烯(St)为单体,正庚烷为致孔剂,偶氮二异丁腈(AIBN)为引发剂,聚乙烯醇(PVA)为分散剂,用悬浮聚合法制备聚合物微球,在转速和分散剂一定的条件下,研究致孔剂用量对聚苯乙烯微球粒径和密度的影响。结果表明,微球的粒径和密度均受致孔剂含量的影响。致孔剂含量影响初始液滴大小、致孔剂均匀分布、液滴中致孔剂和聚苯乙烯比例、相分离难易和微球的溶胀度等方面,这些因素共同影响微球粒径和密度。在实验条件范围内,V(致孔剂)∶V(St)=0.40时制备的微球粒径最大,平均粒径1.6mm;V(致孔剂)∶V(St)=0.80时微球密度最低,为0.899 8g/cm3,漂浮率最高,为96.29%。     

种子溶胀聚合制备苯乙烯-二乙烯苯多孔交联微球

以苯乙烯分散聚合制备单分散种子微球(PS),再用超声分散改进的二步种子溶胀聚合制备了聚苯乙烯-二乙烯苯(PSt-DVB)多孔微球。用光学显微镜、扫描电镜(SEM)和比表面积孔径分布测定仪(BET)等对种子微球和多孔微球的表面形貌及孔结构进行了表征。结果表明,随分散介质极性的增大,所得PS种子微球的粒径变小,相对分子质量增大;固定种子微球用量,随着DBP和DVB用量的增加,交联微球比表面积上升、孔径下降。以乙醇为介质制备种子微球,当DBP体积为1.0 mL,DVB体积为8~10 mL时,能够得到4~7μm单分散性良好的多孔PSt-DVB微球。     

交联聚苯乙烯微球的制备

以聚乙烯醇为分散剂、水为反应介质、过氧化二苯甲酰为引发剂,异戊醇为致孔剂,采用苯乙烯——二乙烯基苯悬浮共聚悬浮聚合的方法,通过优化反应条件,成功制得了平均粒径为0．8mm的多孔微球。研究了引发剂浓度,制孔剂浓度,分散剂浓度和搅拌速度对微球粒径的影响。并用扫描电镜（SEM）对微球进行了表征。     

可降解聚乳酸多孔微球的制备探究

以聚乳酸为壁材,碳酸氢铵为致孔剂,采用双乳液溶剂挥发法,制备出具有孔状的聚乳酸微球,探讨制备条件对聚乳酸微球的影响.结果表明,在内外水相体积比1∶7.5,初乳化搅拌速度1 000 r/min下制得的PLA多孔微球的球形和孔结构较好.     

木质素改性多孔酚醛树脂微球的制备研究

本文以苯酚和甲醛为反应单体,采用聚乙烯醇(PVA1788)作分散剂,三乙胺(TEA)作碱催化剂,六次甲基四胺(HMTA)作交联剂,利用水相悬浮缩聚法制备了球形酚醛树脂。在稳定悬浮缩聚体系引入致孔剂,制备多孔的酚醛树脂微球,并对木质素部分替代苯酚制备多孔酚醛树脂微球进行初步探讨。通过实验确定了水相悬浮缩聚法制备酚醛树脂珠体基本合成工艺:先将苯酚、甲醛、三乙胺加入到一定浓度的PVA水溶液,在95～97℃反应40 min后,加入HMTA,继续反应4 h,再用1 mol/L的盐酸溶液调节pH值至2,固化反应1 h,可得到形态规整的珠体;并发现PVA浓度对酚醛树脂珠体粒度影响很大,粒度分布较宽。甲苯致孔得到多孔球形酚醛树脂微球,粒径分布较无致孔剂时窄,孔径在2μ以上;甲苯用量5 g,PVA浓度为0.375%时,得到的粒径在20～80目间的粒子数量达90%;提高甲苯量能增大多孔球形酚醛树脂微球比表面积,但加宽粒径分布;且高甲苯添加量时,PVA浓度对缩聚产物形态影响非常显著,低PVA浓度下易结块,高PVA浓度下得细粉(粒径小于200目)。邻苯二甲酸二丁酯致孔得到外表面光滑内表面多孔的酚醛树脂中空微球,粒径分布也窄,粒径在20～80目间粒子数量占80%以上。木质素替代苯酚制备多孔球形酚醛树脂,木质素能参与反应成球,但球形度稍差,孔径也更小。     

磁性多孔聚苯乙烯微球的制备

在磁流体存在的情况下,采用改进了的乳液聚合法合成了具有磁核的微米级高分子聚苯乙烯微球。以该微球为种子,采用分散聚合法,以乙二醇／水为分散介质、聚乙二醇为分散剂、甲苯为制孔剂,进行苯乙烯-丙烯酸-二乙烯苯的三元共聚物的合成,最终合成出粒径分布均匀、磁响应性强的磁性多孔聚苯乙烯微球。     

Synthesis of monodisperse crosslinked polystyrene microspheres via dispersion copolymerization with the crosslinker‐postaddition method

Monodisperse crosslinked polystyrene microspheres were prepared by the dispersion copolymerization of styrene and divinylbenzene in a mixed solvent of ethanol and H₂O. 2,2′‐Azobisisobutyronitrile and poly(N‐vinyl pyrrolidone) were used as the initiator and steric stabilizer, respectively. The crosslinker‐postaddition method was adopted through a slow addition of a crosslinking agent into the dispersion system at a certain time after the beginning of the polymerization. The effects of the postaddition recipe, postaddition beginning time, postaddition velocity, and agitation rate on the particle size, size distribution, and morphology were discussed. The resulting polymer microspheres were characterized with scanning electron microscopy and laser particle analysis. Crosslinked polystyrene microspheres with a narrow size distribution and a 12.0% crosslinker level were obtained with a size of 1.0 μm through the crosslinker‐postaddition method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation of polymer microspheres with a rosin moiety from rosin ester,styrene and divinylbenzene

Rosin was reacted with hydroxyethyl methacrylate to produce a macromonomer. This macromonomer was used to partly replace styrene for the novel preparation of polymer microspheres with divinylbenzene via suspension polymerization. Orthogonal experiments were conducted to analyze the factors influencing the particle size, particle size distribution, swelling ratio and degree of crosslinking of the polymer microspheres. Fourier transform IR spectroscopy, thermogravimetry and scanning electron microscopy were used to examine the structures, thermal properties and morphologies, respectively, of the polymer microspheres. The results showed that the amount of dispersant had the greatest influence on particle size and distribution. On the other hand, the monomer ratio greatly influenced the swelling ratio and degree of crosslinking of the polymer microspheres. The decomposition temperature of the polymer microspheres increased upon introduction of the rosin moiety into the product. Open pores were abundant on the surface of the polymer microspheres due to the existence of the porogen, which provided a base for adsorption and separation. The present study opens a novel route for using naturally occurring rosin. Copyright © 2012 Society of Chemical Industry     

用作活性物载体聚苯乙烯-二乙烯苯多孔交联微球的悬浮聚合制备及表征

Functional porous microspheres used for the slow release carrier of actives in cosmetics or pharmaceuticals were prepared by modified suspension polymerization of styrene （ST） with divinylbenzene （DVB） in the presence of toluene, cyclohexanol and heptane as porogenic diluents. The use of ultrasonic dispersion decreases the beads＇ size and improves the uniformity. The effects of the porogen mixture, DVB content and solvent extraction on the surface performance of the synthesized beads were studied. The microspheres were characterized by scanning electron microscopy （SEM） and BET surface area determination. It was found that a great proportion of the non-solvating porogen increases the pore diameter and the specific surface area. High DVB concentration also results in the great specific surface area and porosity. When the ratio of toluene/cyclohexanol is 1：2, DVB content is at the range of 40%-60% and methylene chloride was used as extractant, the beads with good spherical shape and pore size were obtained. The prepared porous microspheres were applied as active carriers and showed satisfactory slow release effect. Over 10h constantly sustained release was observed in vitro releasing test for hydroquinone-loaded microspheres. Great surface area promoted high concentration of released hydroquinone.     

Carbonization of PAN grafted uniform crosslinked polystyrene microspheres

Micrometer-sized polystyrene/poly(styrene-divinylbenzene) and polystyrene/polydivinylbenzene composite particles of narrow size distribution were formed by a single-step swelling process of uniform polystyrene template particles with emulsion droplets of dibutyl phthalate containing benzoyl peroxide and divinylbenzene in the presence or absence of styrene, followed by polymerization of the monomer(s) within the swollen template particles at 70 °C. Porous poly(styrene-divinylbenzene) and polydivinylbenzene uniform microspheres were formed by dissolution of the polystyrene part of the former composite particles. Hydroperoxide conjugated microspheres were formed by ozonolysis of the former porous microspheres. Uniform poly(styrene-divinylbenzene)/PAN and polydivinylbenzene/PAN core/shell microspheres were prepared by room temperature redox graft polymerization of AN onto the hydroperoxide conjugated particles. Uniform carbon microspheres were prepared by carbonization of the core/shell particles at 800 and 1100 °C under dynamic N₂ atmosphere. On the other hand, a similar treatment of the core particles only resulted in destruction of the particle shape. Carbon microspheres of increasing surface area (up to ca. 1000 m²/g) were prepared by activation of the former carbon microspheres with CO₂ at 850 °C. The influence of the carbonization temperature of the core/shell particles and the activation time of the carbon particles on the carbon yield and surface area has been elucidated.     

Monodisperse polymer beads as packing material for high-performance liquid chromatography

A novel approach to monodispersed porous polymer beads allowing accurate control over a broad range of pore size distribution has been developed. It involves the use of monodispersed template particles which are used as polymeric porogens in the suspension polymerization of monomers such as styrene and divinylbenzene. The size uniformity of the template particles is retained by the final porous beads. The porous properties of the final beads are determined in large part by the characteristics of the porogenic mixture such as its composition, the molecular weight of the polymeric porogen, as well as the relative amount of monomers, polymeric and low molecular weight porogens used.     

2‐Hydroxyethylmethacrylate carrying uniform porous particles: preparation and electron microscopy

Uniform macroporous particles carrying hydroxyl groups have been obtained in the size range 3–11.5 µm by seeded polymerization. For this purpose, uniform polystyrene particles in the size range 1.9–6.2 µm were used as seeds. The seed particles were successively swollen by dibutyl phthalate (DBP) and a monomer mixture comprising styrene, 2‐hydroxyethylmethacrylate (HEMA) and a crosslinker. Two different crosslinkers, divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA), were tested. Size distribution properties together with bulk and surface structures of the particles have been characterized by both scanning and transmission electron microscopy. While EGDMA provides uniform particles with a non‐porous surface, DVB produces uniform particles having a highly porous surface and interior. The comparison of FTIR and FTIR‐DRS spectra shows that the HEMA concentration is higher on the particle surface than within the particle interior. Seed latex size and monomer/seed latex ratios are identified as the most important variables affecting the final particles. Different seed latexes have been tried; the result is that highly macroporous particles with a sponge‐like pore structure both on the surface and in the particle interior have been obtained by use of the seed latex with the largest particles and the lowest molecular weight. An increase in the HEMA feed concentration leads to final particles with a non‐porous surface and a crater‐like porosity in the particle interior. The average pore size significantly decreases with increasing DBP/seed latex and monomer/seed latex ratios. © 2001 Society of Chemical Industry     

Electron microscopic observation of uniform macroporous particles. II. Effect of DVB concentration

The electron microscopic observation of uniform and macroporous poly(styrene‐co‐divinylbenzene) particles prepared by a two‐step seeded polymerization method was performed. In the synthesis of uniform macroporous particles, the uniform polystyrene latices produced by a dispersion polymerization method with two different sizes and average molecular weights were utilized as the seed particles. The seed particles were first swollen with dibutylphthalate and then with a monomer phase, including styrene and divinylbenzene. The macroporous structure of the final particles was achieved by using a porogen mixture consisting of dibutylphthalate and linear polystyrene. The linear polystyrene part of the porogen solution was directly obtained from the seed latex. The macroporous particles with different diameters and porosities were produced by changing the divinylbenzene concentration between 25 and 100% in the repolymerization step. The effect of divinylbenzene concentration on the size and the surface morphology of the final particles were investigated by scanning electron microscopy. The internal structure of the final particles was analyzed by transmission electron microscopy. The results indicated that the average size of the final particles increased with the increasing divinylbenzene concentration. The increase in the DVB concentration also led to an increase in the average pore size. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2291–2302, 1999     

快速膜乳化法制备尺寸均一及结构可控聚苯乙烯微粒

以苯乙烯为单体、二乙烯基苯为交联剂,采用快速膜乳化法制备了聚苯乙烯微粒,对其粒径分布、制备重复性、颗粒结构进行了表征,并考察了致孔剂种类及用量对不同粒径颗粒形态结构的影响规律. 结果表明,聚苯乙烯颗粒粒径与所用膜孔径呈线性关系,最佳乳化压力与膜孔径呈反函数关系. 优化工艺条件下所制颗粒粒径为1~6 mm,粒径分布系数均小于0.8,批次相对标准偏差低于3%. 体积效应对小粒径颗粒的成型结构影响较大;粒径越小,颗粒成型时致孔剂与聚合物间的相分离程度越低,颗粒粒径小于2 mm时液体石蜡无法形成完整颗粒,颗粒粒径大于2 mm时十六烷用量在60%(w)以下才能形成大孔结构.     

Influence of chelating agent and reaction time on the swelling process for preparation of porous TiO2 particles

This study aimed to describe the preparation and characterization of porous titanium oxide particles of narrow particle size distribution by a single-step swelling process of polystyrene template microspheres. In this research, different specific surface areas, porous structures and densities of porous titanium oxide particles had been synthesized with various experimental parameters. Two main parameters were tested and discussed: (1) acetylacetone amount (from 0 to 1 ml) and (2) reaction time (from 2 to 32 h). Polystyrene template particles were polymerized by emulsifier free-emulsion polymerization (a kind of polymerization method). For the swelling process to be successful, a chelating agent (acetylacetone) was added to delay the aqueous hydrolysis of titanium (IV) isopropoxide in the water phase. The influences of various reaction parameters on size, morphology, composition, specific surface area, porous structure and density of particles were investigated. The properties of particles were analyzed by scanning electron microscope, Brunauer–Emmett–Teller, Fourier transform infrared analysis, thermogravimetric analysis, powder X-ray diffraction, and specific gravity meter.     

7-氨基-4-甲基香豆素分子印迹纳米球的制备与研究

采用单步溶胀法,在单分散纳米级聚苯乙烯微球为种球的基础上,以α-甲基丙烯酸为功能单体,二甲基丙烯酸乙二醇酯为交联剂,乙腈作为制孔剂,7-氨基-4-甲基香豆素(AMC)作为模板分子,成功制得了多孔单分散分子印迹聚合物。通过扫描电镜、紫外光谱和红外光谱等手段对聚合物进行了表征,研究表明,所制得的MIPs平均粒径为200~300 nm,表面粗糙,具有一定孔径,特异吸附性能良好。分析显示,MIPs在识别6-甲基香豆素的过程中存在两类结合位点,高亲和力结合位点的平衡离解常数KD1=49.019μmol·L-1,Bmax1=29.162μmol·g-1;低亲和力结合位点的KD2=84.034μmol·L-1,Bmax2=40.017μmol·g-1。