Preparation of micron-size monodisperse poly(2-hydroxyethyl methacrylate) particles by dispersion polymerization

Dispersion polymerization of 2-hydroxyethyl methacrylate using four categories of polymeric stabilizers in a mixture of good and poor solvents was performed to produce polymeric particles. The stabilizers employed were methyl methacrylate and styrene homopolymers, methacryloyl-terminated poly(methyl methacrylate) and polystyrene macromonomers, an amphiphilic poly(methyl methacrylate-co-methacrylic acid-graft-styrene), and polybutadiene derivatives containing reactive vinyl groups. Dispersion copolymerization with a small amount of the macromonomer gave micron-size particles with relatively narrow size distribution. The amphiphilic graft copolymer and the polybutadiene derivatives also afforded monodisperse particles. The mixed ratio between good and poor solvents greatly affected the particle size and size distribution. © 1996 John Wiley & Sons, Inc.     

Synthesis and emulsion copolymerization of amphiphilic poly(2-oxazoline) macromonomer possessing a vinyl ester group

The present article describes the synthesis and emulsion copolymerization of a block-type amphiphilic poly(2-oxazoline) macromonomer possessing a polymerizable vinyl ester group. The macromonomer was synthesized by one-pot two-stage block copolymerization of 2-oxazolines using vinyl iodoacetate as initiator. 2-Methyl- and 2-n-butyl-2-oxazolines were employed for the construction of hydrophilic and hydrophobic segments, respectively. The surface activities evaluated by the surface tension of the macromonomer in water were fairly good. Emulsion copolymerization of vinyl acetate with the macromonomer was carried out. The macromonomer acted as a polymeric surfactant, as well as a comonomer. The resulting copolymer latex particles were spherical and their diameter was in the sub-micron range. The effects of the composition of the macromonomer on the emulsion copolymerization and the resulting latex particles were examined. © 1993 John Wiley & Sons, Inc.     

Synthesis of graft copolymer from copolymerization of styrene‐terminated poly(ethylene oxide) macromonomer and styrene with CpTiCl3/methylaluminoxane catalyst

Copolymerization of styrene (St) and St‐terminated poly(ethylene oxide) macromonomer (SEOM) with CpTiCl₃/methylaluminoxane (MAO) catalyst in toluene was investigated. The copolymerization of St and SEOM proceeded easily to give a graft copolymer consisting of syndiotactic polystyrene as the main chain and hydrophilic poly(ethylene oxide) as the side chain. A number of side chains in the graft copolymer could be controlled by the amount of SEOM in the feed. The reactivity of SEOM was determined from copolymerization of St and SEOM with the CpTiCl₃/MAO catalyst, and the reactivity of SEOM depended on the molecular weight of SEOM. The thermal properties of the graft copolymer such as the melting temperature were influenced by the introduction of SEOM. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2904–2910, 2004     

Morphological investigation of styrene and acrylamide polymer microspheres prepared by dispersion copolymerization

 The morphology of the styrene and acrylamide copolymer microspheres prepared by dispersion copolymerization in an ethanol/water medium was investigated. The effects of the styrene/acrylamide ratio, ethanol/water ratio and stabilizer concentration on the particle size and size distribution were studied. It was found that the initial solubility parameter of the system was the key factor in the process. The comonomer acrylamide also played an important role in the particle size and size distribution in the presence of cross-linking agent (divinylbenzene). Received: 29 October 1999 Accepted in revised form: 29 November 1999     

基于聚(2-甲基-2-噁唑啉)和聚丙烯酸的混合刷在毛细管电泳在线富集溶菌酶中的应用

制备了一种对溶菌酶具有可控吸附性能的混合刷涂层毛细管,用于毛细管电泳在线富集溶菌酶以提高其检测灵敏度。首先,分别通过阳离子开环聚合和可逆加成-断裂链转移（RAFT）聚合合成聚（2-甲基-2-噁唑啉）（PMOXA）和聚丙烯酸（PAA）,然后将甲基丙烯酸缩水甘油酯（GMA）分别与PMOXA和PAA通过自由基共聚和RAFT聚合合成出聚（2-甲基-2-噁唑啉）-r-甲基丙烯酸缩水甘油酯（PMOXA-r-GMA）和聚丙烯酸-b-聚甲基丙烯酸缩水甘油酯（PAA-b-PGMA）。将PMOXA-r-GMA和PAA-b-PGMA的混合溶液以一定比例加入到毛细管内,通过加热即可制备出基于PMOXA和PAA的混合刷涂层毛细管。X射线光电子能谱（XPS）对毛细管原材料的表面组成研究结果表明,当混合溶液质量浓度为20 g/L、PMOXA-r-GMA和PAA-b-PGMA质量比为1：1时,所得涂层中羧基的含量随着PAA链长的增加而增加;异硫氰酸荧光素标记溶菌酶（FITC-溶菌酶）吸附实验结果显示,通过改变环境的pH和离子强度（I）可以调控涂层毛细管对溶菌酶的吸附和释放,在pH 7（I=10^-5mol/L）条件下,毛细管可以吸附大量的溶菌酶,当条件变为pH 3（I=10^-1mol/L）时,吸附的溶菌酶可以被释放出来。将这种具有溶菌酶可控吸附性能的涂层毛细管用于毛细管电泳在线富集溶菌酶,当PAA链长是PMOXA链长的2.2倍时,溶菌酶的灵敏度增强因子为17.69,检出限为8.7×10^-5g/L;同一天内对溶菌酶连续测定5次以及连续测定5天,峰面积的日内、日间相对标准偏差（RSD）分别为2.9%和4.1%,迁移时间的日内、日间RSD分别为0.9%和2.1%。涂层的制备只需一步,简单易行,而且涂层具有很好的稳定性。本研究为毛细管电泳分析痕量蛋白质提供了一种简单有效的方法。     

Preparation and properties of poly(alkyl vinyl ether-2-ethyl-2-oxazoline) diblock copolymers

A method for the synthesis of well-defined poly(alkyl vinyl ether–2-ethyl-2-oxazoline) diblock copolymers with hydrolytically stable block linkages has been developed. Monofunctional poly(alkyl vinyl ether) oligomers with nearly Poisson molecular weight distributions were prepared via a living cationic polymerization method using chloroethyl vinyl ether together with HI/ZnI₂ as the initiating system and lithium borohydride as the termination reagent. Using the resultant chloroethyl ether functional oligomers in combination with sodium iodide as macroinitiators, 2-ethyl-2-oxazoline was polymerized in chlorobenzene/NMP to afford diblock copolymers. A series of poly(methyl vinyl ether–2-ethyl-2-oxazoline) diblock materials were found to have polydispersities of ≈ 1.3–1.4 and are microphase separated as indicated by two T_g's in their DSC thermograms. These copolymers are presently being used as model materials to study fundamental parameters important for steric stabilization of dispersions in polar media. © 1993 John Wiley & Sons, Inc.     

PVA-g-PS复合微球的制备与粒径控制研究

由链转移自由基聚合与端基置换反应法,合成了苯乙稀基单封端的聚醋酸乙烯酯(PVAc)大分子单体,使其与苯乙烯在乙醇/水的混合介质中进行自由基分散共聚,得到了表面以PVAc为接枝链的聚苯乙烯(PVAc-g-PSt)微球。将所得微球在碱性条件下醇解,形成了以亲水性聚乙烯醇(PVA)为壳、聚苯乙烯为核的复合微球(PVAc-g-PSt)。用核磁共振对聚合物的结构进行表征,定出了PVAc末端双键的含量;并用激光光散射、扫描电子显微镜对微球的粒径与形态进行了表征。研究结果表明,在共聚反应体系中大分子单体的分子量与浓度、苯乙烯浓度、引发剂浓度及溶剂的组成对微球的形态和粒径大小有明显影响。     

Preparation and control of surface properties of monodisperse micrometer size beads by dispersion copolymerization of styrene and butyl methacrylate in polar media

The dispersion copolymerization of styrene and butyl methacrylate in ethanol-water medium to afford micrometer-size monodisperse beads has been investigated. Hydroxypropyl cel-lulose, poly (acrylic acid), and poly (vinylpyrrolidone) have been used as steric stabilizers, benzoyl peroxide and azobisisobutyronitrile as initiators. A novel steric stabilizing system consisting of a mixture of poly (acrylic acid) and hydroxypropyl cellulose has also been shown to lead to monodisperse beads for which the surface charge can be controlled by the relative ratio of steric stabilizers. The effect of several variables, such as the solvency of the medium, the concentration of co-monomers, the reaction temperature, and the type of steric stabilizer and initiator used on the bead size and size distribution are discussed. © 1995 John Wiley & Sons, Inc.     

Reactive poly(glycidyl methacrylate) microspheres prepared by dispersion polymerization

Poly(glycidyl methacrylate) [poly(GMA)] microspheres of narrow size distribution were prepared in a simple one‐step procedure by dispersion radical polymerization. Depending on the solvent used, poly(GMA) particle size could be controlled in the range of 0.5–4 μm by changing the solubility parameter of the reaction mixture. In N,N′‐dimethylformamide (DMF)/methanol mixture, the particle size increased and the size distribution broadened with decreasing initial solubility parameter. While in the DMF/methanol solvent system, hydroxypropyl cellulose (HPC) or cellulose acetate butyrate (CAB) were taken as steric stabilizers of the dispersion polymerization, poly(vinylpyrrolidone) (PVP) was used in alcoholic media. Contrary to the DMF/methanol system, narrow particle size distributions were obtained with PVP‐stabilized polymerizations in ethanolic, methanolic, propan‐1‐olic or butan‐1‐olic medium. Both the particle size and polydispersity were reduced with increasing stabilizer concentration. If lower molecular‐weight PVP was used, larger microspheres were obtained. Poly(GMA) samples prepared in a neat alcoholic medium virtually quantitatively retained oxirane group content after the polymerization. Reactivity of the poly(GMA) microspheres was confirmed by their hydrolysis and aminolysis. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3855–3863, 2000     

Synthesis and characterization of monodisperse porous polymer particles

Monodisperse porous polymer particles in the size range of 10 μm in diameter were prepared via seeded emulsion polymerization. Linear polymer (polystyrene seed) or a mixture of linear polymer and solvent or nonsolvent were used as inert diluents. The pore diameters of these porous polymer particles were on the order of 1000 Å with pore volumes up to 0.9 mL/g and specific surface areas up to 200 m²/g. The physical features of the porous polymer particles depended on the diluent type and the crosslinker content, as well as the molecular weight of polymer seed particles. By varying the molecular weight of the linear polymer, monodisperse porous polymer particles with different pore size distribution could be synthesized. Polymer seed with a low degree of crosslinking instead of linear polymer could also be used to prepare monodisperse porous polymer particles with smaller pore volume and pore size.     

Mesomorphic phase formation of poly (macromonomer)s of polystyrene macromonomers

The liquid crystalline phase formation of poly(macromonomer)s associated with the specific multibranched architecture of high branch density was investigated. The poly(macromonomer)s were prepared by radical chain polymerizations of ω‐methacryloyloxyethyl polystyrene macromonomers. It was confirmed that the mesomorphic phase formation depended on the branching architecture, where sufficient length of the branch chains as well as the backbone chain is crucial for the formation of the mesomorphic phase. Formation of the optically anisotropic mesophase also depended on the nature of solvent. The mesophase was observed in the cast films prepared from p‐xylene, toluene, tetrahydrofuran, carbon disulfide and chloroform but not observed for cyclohexane. The effects of the branched structure and the solvent nature were explained by repulsive interaction between the polystyrene branch chains of high branch density. The repulsive interaction increases the chain stiffness of the central backbone and also prevents the interpenetration of the polystyrene branches of different molecules in solution, which allow poly(macromonomer) molecules to arrange with the orientational order. Copyright © 2000 John Wiley & Sons, Ltd.     

Graft copolymers having hydrophobic backbone and hydrophilic branches. XXIII. Particle size control of poly(ethylene glycol)-coated polystyrene nanoparticles prepared by macromonomer method

Monodisperse polymeric nanospheres, which consist of polystyrene cores and poly(ethylene glycol) (PEG) branches on their surfaces, were prepared by the dispersion copolymerization of styrene (St) with PEG macromonomers that had a methacryloyl (MMA-PEG) or p-vinylbenzyl (St-PEG) end group in various organic solvent/water media. Electron spectroscopy for chemical analysis (ESCA) of the nanosphere surfaces indicated that PEG macromonomer chains were favorably located on their surfaces. The morphologies of the nanospheres were observed via a scanning electron micrograph (SEM), and particle sizes were estimated by a submicron particle analyzer. When both the concentration of macromonomers and molecular weight were higher, small nanospheres in diameter were obtained. Larger nanospheres in diameter were obtained using macromonomers with low molecular weight at lower concentration. The functions that correlate the diameter (D_n) on different concentration units were D_n = K[St]^0.64[MMA-PEG]^{−0.53±0.01}[I]^−0.49 and D_n = K[St]^0.80[St-PEG]^{−0.69±0.01}[I]^−0.22, where [I], [St], [MMA-PEG], and [St-PEG] are initiator, styrene, MMA-PEG, and St-PEG macromonomer concentration in feed, respectively. When the reaction parameters such as the molecular weight of the macromonomers were properly chosen, the particle size could be controlled in a range from ca. 80 to 3100 nm. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2155–2166, 1999     

Nanosphere formation in copolymerization of methyl methacrylate with poly(ethylene glycol) macromonomers

Polymeric nanospheres consisting of poly(methyl methacrylate) (PMMA) cores and poly(ethylene glycol) (PEG) branches on their surfaces were prepared by free radical copolymerization of methyl methacrylate (MMA) with PEG macromonomers in ethanol/water mixed solvents. PEG macromonomers having a methacryloyl (MMA‐PEG) and p‐vinylbenzyl (St‐PEG) end group were used. It has become clear that the obtained polymer dispersions form three kinds of states, particle dispersion (milky solution), clear solution, and gel/precipitation. It was found that the reaction parameters such as MMA concentration, molecular weight, and concentration of PEG macromonomers, and water content can affect nanosphere formation in a copolymerization system. The water volume fraction of mixed ethanol/water solvents affected the particle size of the nanospheres. These differences in the formation of nanospheres were due to the solvophilic/solvophobic balance between the copolymers and solvents during the self‐assembling process of the copolymers. The sizes of nanospheres can be controlled by varying concentration of PEG macromonomer and water content in solvents. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1811–1817, 2000     

聚(2-甲基-2-噁唑啉)在毛细管电泳分离蛋白质中的应用

毛细管电泳作为一种常见的液相分离技术,因其分析速度快、分离效率高、样品消耗量少等特点,在蛋白质分离分析领域有广泛应用。然而,常用的熔融硅毛细管容易吸附蛋白质,导致电渗流不稳定,分离结果重现性变差;此外,商用毛细管电泳中常用的紫外检测器由于光程短,使得毛细管电泳的检测灵敏度往往不能达到低丰度蛋白质的直接分析要求。因此寻找能够阻止蛋白质吸附、同时能够提高检测灵敏度的涂层是毛细管电泳分离分析蛋白质的重要课题之一。聚（2-甲基-2-噁唑啉）（PMOXA）作为一种类肽类亲水性聚合物,具有与抗蛋白质吸附聚合物聚乙二醇类似的亲水性、抗蛋白质吸附性和生物相容性,而且其类肽结构使之具有较聚乙二醇更好的稳定性,因此近年来在生物质传递、药物载体和阻抗蛋白质吸附等领域得到越来越多的应用。该文主要从两个方面对聚（2-甲基-2-噁唑啉）在毛细管电泳中的应用进行了阐述。一是利用多巴胺作为黏合层将其涂覆在毛细管内壁作为抗蛋白质吸附涂层,这种涂层不仅能成功分离多种蛋白质的混合物（如溶菌酶、细胞色素C、核糖核酸酶A和α-胰凝乳蛋白酶原A）,而且在定量检测奶粉中三聚氰胺、乳铁蛋白的过程中,能阻抗其他蛋白质的非特异性吸附,提高了毛细管电泳对奶粉中三聚氰胺、乳铁蛋白的检测效率。二是将其与具有刺激响应性的聚合物（如聚丙烯酸）构成二元混合刷涂层,在一定的pH和离子强度条件下,涂层可吸附目标蛋白质（如牛血清白蛋白、溶菌酶）,在另一pH和离子强度条件下可将吸附的目标蛋白质全部释放,同时在释放过程中,处于涂层表面的聚（2-甲基-2-噁唑啉）会进一步阻止蛋白质的吸附,释放的蛋白质在电渗流和电泳的双重作用下快速迁移,到达检测器的蛋白质瞬时浓度大大增加,使目标蛋白质得到富集,目标蛋白质的检测信号得到放大,从而达到了提高低丰度蛋白质检测灵敏度的目的。此外,该文还对聚（2-甲基-2-噁唑啉）在毛细管电泳分离蛋白质中的未来发展趋势进行了展望。     

An effective cross-linking of polymer layer on monodisperse, poly(maleic anhydride-styrene)-modified colloidal silica particles and properties of the composite

Summary  The cross-linkings of the surface polymer layer on mono disperse, poly(maleic anhydride-styrene)-modified silica particles by the reaction with diisocyanate were studied. The extent of cross-linking was estimated by the weight decrease by immersing the particles in the buffer solution of pH 2.0, 4.0 and 9.0 at a room temperature for 24 h. The reaction of the polymer-modified silica with 1,6-diisocyanatohexane afforded relatively stable composite particles which lost less than 5 wt% of the polymer in aqueous solution in the pH range 2.0–9.0. The diisocyanate was a preferable cross-linker to 2,4-diisocyanatotoluene in terms of stability in acidic or basic aqueous solution. The flexibility of the cross-linker molecule possibly plays an important role in the cross-linking reaction. The carboxyl and amino groups were formed by treating the cross-linked composite particles with diluted HCl solution; 5–6 and 0.5–1.1 μmol g^-1, respectively. The cross-linked composite particles exhibited the characteristic property of ζ-potential, −44 to −47 mV and −102 to −107 mV in a neutral aqueous solution and ethanol, respectively. Received: 26 May 1997 Accepted: 4 August 1997     

Dispersion copolymerization of styrene and divinylbenzene: Synthesis of monodisperse,uniformly crosslinked particles

Monodisperse, crosslinked polystyrene latexes were prepared by the dispersion technique. Some general observations regarding the effect of initial reagent concentrations on final particle size and size distribution are offered, in addition to a detailed discussion concerning the problems encountered with the use of the crosslinker divinylbenzene (DVB) in latex preparation. Particles synthesized in very polar media were found to reach their growth plateau sooner than those made in less polar surroundings. This trend was proposed to be the result of more effective nucleation in polar environments, which increases available surface area, thereby allowing the rapid replacement of monomer consumed within the particle phase during the polymerization. Attempts to favorably influence the growth rate and size distribution of particles during the reaction were unsuccessful, underlining the importance of the nucleation period in defining particle size characteristics. Up to 1% DVB was successfully incorporated in the synthesis of coagulum-free, monodisperse, 5 μm beads, by controlling the entry of the crosslinker into the particle phase during the major particle growth period. Latex stability is proposed to be largely dependent on the mobility of the adsorbed steric stabilizer. © 1995 John Wiley & Sons, Inc.     

Preparation of P4VP-g-PSt Copolymer Microspheres with Controllable Size by Atom Transfer Radical Polymerization Synthesized Poly(4-vinylpyridine) Macromonomer

Poly(4‐vinylpyridine) macromonomer (St‐P4VP) with a styryl end group was synthesized by atom transfer radical polymerization (ATRP) of 4‐vinylpyridine using p‐(chloromethyl)styrene (CMSt) as functional initiator, CuCl as catalyst and tris[2‐(dimethylamino)ethyl]amine (Me₆TREN) as ligand in 2‐propanol. The structure of St‐P4VP macromonomer was identified by proton nuclear magnetic resonance (¹H NMR). The result of gel permeation chromatography (GPC) illustrated that the number‐average molecular weight of St‐P4VP could be controlled by adjusting polymerization conditions. Poly(4‐vinylpyridine) grafted polystyrene microspheres (P4VP‐g‐PSt) were then prepared by dispersion copolymerization of styrene with St‐P4VP macromonomers. The effects of polymerization reaction parameters such as medium polarity, concentration of St‐P4VP macromonomer and polymerization temperature on the sizes and size distribution of P4VP‐g‐PSt microspheres were investigated. The results of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and laser light scattering (LLS) indicated that mono‐dispersed P4VP‐g‐PSt microspheres with average diameters of 100–200 nm could be obtained when the molar ratio of St to St‐P4VP was 0.25:100 in ethanol/water mixed solvents (V/V=80:20) at 60°C. Such kind of graft copolymer microspheres was expected to be applied to many fields such as drug delivery system and protein adsorption/separation system due to their particular structure.     

Polystyrene‐graft‐poly(ethylene oxide) copolymers prepared by macromonomer technique in dispersion. I. Liquid chromatographic separation of product mixtures

Products of the radical dispersion copolymerization of methacryloyl‐terminated poly(ethylene oxide) (PEO) macromonomer and styrene were separated and characterized by size exclusion chromatography (SEC), full adsorption‐desorption (FAD)/SEC coupling and eluent gradient liquid adsorption chromatography (LAC). In dimethylformamide, which is a good solvent for PEO side chains but a poor solvent for polystyrene (PS), amphiphilic PS‐graft‐PEO copolymers formed aggregates, which were very stable at room temperature even upon substantial dilution. The aggregates disappeared at high temperature or in tetrahydrofuran (THF), which is a good solvent for both homopolymers and for PS‐graft‐PEO. FAD/SEC procedure allowed separation of homo‐PS from graft‐copolymer and determination of both its amount and molar mass. Effective molar mass of graft‐copolymer was estimated directly from the SEC calibration curve determined with PS standards. Presence of larger amount of the homo‐PS in the final graft‐copolymer products was also confirmed with LAC measurements. The results indicate that there are at least two or maybe three polymerization loci; namely the continuous phase, the particle surface layer and the particle core. The graft copolymers are produced mainly in the continuous phase while PS or copolymer rich in styrene units is formed mostly in the core of monomer‐swollen particles. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2284–2291, 2000     

Preparation of micron-size monodisperse polymer microspheres having chloromethyl group

Micron-size monodisperse polymer microspheres having chloromethyl groups thereon were prepared by two-step polymerization process as follows. First, micron-size monodisperse polystyrene particles were prepared by dispersion polymerization with 2,2-azobisisobutyronitrile as initiator in ethanol-water medium in the presence of poly(acrylic acid) as stabilizer under various conditions. Secondly, in the presence of the 1.9-m monodisperse polystyrene particles produced under the optimum conditions, seeded copolymerization for styrene and chloromethyl styrene was carried out. The seeded copolymerization proceeded smoothly without producing new particles, and it was confirmed by x-ray photoelectron spectroscopy that the chloromethyl group existed more at the surface of the produced microsphere than at that of film cast from the benzene solution in which the microspheres were dissolved.Part CVI of the series Studies on Suspension and Emulsion.