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     

Photoinitiated dispersion polymerization of methyl methacrylate: A quick approach to prepare polymer microspheres with narrow size distribution

Photoinitiated dispersion polymerization of methyl methacrylate was carried out in a mixture of ethanol and water as dispersion medium in the presence of poly(N‐vinylpyrrolidone) (PVP) as the steric stabilizer and Darocur 1173 as photoinitiator. 93.7% of conversion was achieved within 30 min of UV irradiation at room temperature, and microspheres with 0.94 μm number–average diameter and 1.04 polydispersity index (PDI) were obtained. X‐ray photoelectron spectroscope (XPS) analysis revealed that only parts of surface of the microspheres were covered by PVP. The particle size decreased from 2.34 to 0.98 μm as the concentration of PVP stabilizer increased from 2 to 15%. Extra stabilizer (higher than 15%) has no effect on the particle size and distribution. Increasing medium polarity or decreasing monomer and photoinitiator concentration resulted in a decrease in the particle size. Solvency of reaction medium toward stabilizer, which affects the adsorption of stabilizer on the particle surface, was shown to be crucial for controlling particle size and uniformity because of the high reaction rate in photoinitiated dispersion polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1329–1338, 2008     

Dispersion copolymerization of styrene and butyl acrylate in polar solvents

Monodisperse copolymer particles from 1.1 to 2.6 μm in diameter were obtained by unseeded batch dispersion copolymerization of styrene and butyl acrylate in an ethanol–water medium. A two-level factorial design using bottle polymerizations was initially carried out including the following variables: stabilizer concentration, initiator concentration, polarity of the dispersion medium, initial monomer concentration, and temperature. Once the region of experimental conditions in which monodisperse latexes can be prepared was identified, further effort was devoted to analyze the effect of other variables. It was found that the temperature at which nucleation occurs and the evolution of the temperature after the onset of nucleation were critical to obtain monodisperse particles. The particle size increased with increasing initial monomer concentration and ethanol–water weight ratio, and decreasing stabilizer concentration. A minimum quantity of emulsifier was necessary to avoid coalescence of particles and to obtain monodisperse particles. © 1996 John Wiley & Sons, Inc.     

分散聚合制备粒度均匀的聚甲基丙烯酸环氧丙酯微球

文中描述了粒度均匀的聚甲基丙烯酸环氧丙酯微球的制备,所采用的是分散聚合方法,系统地研究了溶剂体系、单体浓度、引发剂类型与浓度、稳定剂用量、反应温度等各种聚合参数,对聚合产物粒度及其分散性的影响．在优化反应条件的基础上,制备出了微米级（１～８μｍ）粒度均匀性基本呈现单分散的聚合物微球．     

Synthesis of highly crosslinked monodisperse polymer particles: Effect of reaction parameters on the size and size distribution

Monodisperse polystyrene particles crosslinked with different concentrations of divinylbenzene were synthesized in the 3.2–9.1 μm size range by dispersion polymerization in an isopropyl alcohol/toluene mixed‐dispersion medium with poly(N‐vinylpyrrolidone) as a steric stabilizer and 2,2′‐azobisisobutyronitrile as a radical initiator. The effects of the reaction parameters such as the crosslinking agent concentration, media solvency (controlled by varying the amount of toluene addition), the initiator concentration, and the stabilizer concentration on the particle size and size distribution were investigated with reference particles with a monodisperse size distribution and crosslinked by 1.5 wt % divinylbenzene. The appropriate increase in media solvency was a prerequisite for preparing crosslinked particles without coagulated and/or odd‐shaped particles. The investigation of the effects of the polymerization parameters also shows that only specific sets of conditions produce particles with a monodisperse size distribution. The glass‐transition temperatures of the particles increased with increasing divinylbenzene concentration. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4368–4377, 2002     

Nonaqueous dispersion polymerization of styrene in methanol with the ionomer block copolymer poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)]‐b‐polyisobutene as a stabilizer

The nonaqueous dispersion polymerization of styrene in methanol with poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)]‐b‐polyisobutene as a stabilizer was investigated. There was no observable inducing period or autoacceleration in the polymerization process. The conversion increased almost linearly with the polymerization time as high as 80%. The average sizes of the obtained polystyrene particles increased, and the size distributions of the polystyrene particles tended to become narrower, with increasing conversion. The mechanism of the dispersion polymerization in the presence of polyisobutene‐b‐poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)] was nucleation/growth. When the stabilizer/monomer ratio (w/w) was greater than 2.0%, the polystyrene dispersion was stable, and there was no observable polymer particle coagulation taking place during the whole polymerization process. The average diameter of the polymer particles can be mediated through changes in the polymerization conversion, monomer, and stabilizer. Nearly monodispersed polystyrene particles with average diameters of approximately 0.45–2.21 μm were obtained under optimal conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2678–2685, 2004     

Poly(2‐hydroxyethyl methacrylate‐co‐N,O‐dimethacryloylhydroxylamine) particles by dispersion polymerization

Poly(2‐hydroxyethyl methacrylate‐co‐N,O‐dimethacryloylhydroxylamine) particles were prepared by dispersion polymerization in toluene/2‐methylpropan‐1‐ol medium using cellulose acetate butyrate and dibenzoyl peroxide (BPO) as a steric stabilizer and initiator, respectively. The particle size was reduced with decreasing solvency of the reaction medium (more nuclei were generated) because the critical chain length of the precipitated oligomers decreased with an increasing toluene content, which is a poorer solvent for the polymer than 2‐methylpropan‐1‐ol. There is an optimum initiator concentration (2 wt % BPO relative to monomers) for producing low‐polydispersity particles under given conditions. Additionally, discrete spherical particles were obtained at a low monomer concentration and/or higher polymerization temperature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1625–1632, 2002     

Poly(N,N‐diethylacrylamide) microspheres by dispersion polymerization

Poly(N,N‐diethylacrylamide)‐based microspheres were prepared by ammonium persulfate (APS)‐initiated and poly(vinylpyrrolidone) (PVP)‐stabilized dispersion polymerization. The effects of various polymerization parameters, including concentration of N,N′‐methylenebisacrylamide (MBAAm) crosslinker, monomer, initiator, stabilizer and polymerization temperature on their properties were elucidated. The hydrogel microspheres were described in terms of their size and size distribution and morphological and temperature‐induced swelling properties. While scanning electron microscopy was used to characterize the morphology of the microspheres, the temperature sensitivity of the microspheres was demonstrated by dynamic light scattering. The hydrodynamic particle diameter decreased sharply as the temperature reached a critical temperature ～ 30 °C. A decrease in the particle size was observed with increasing concentration of both the APS initiator and the PVP stabilizer. The microspheres crosslinked with 2–15 wt % of MBAAm had a fairly narrow size distribution. It was found that the higher the content of the crosslinking agent, the lower the swelling ratio. High concentration of the crosslinker gave unstable dispersions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6263–6271, 2008     

Preparation of methyl methacrylate and glycidyl methacrylate copolymerized nonporous particles

Particles of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) copolymer having narrow size distributions were prepared by the method of dispersion polymerization. Results from the analysis of particle porosity and the correlation of specific surface area with the reciprocal of particle diameter suggest that the prepared particles were nonporous. The particle size was found to decrease from 4.2 to 2.1 μm with increasing the mass ratio of GMA/MMA from 0.1 to 0.75. Polymer particles having an average diameter falling in this range are suitable for being employed as the stationary phase in protein chromatography. The decrease in particle size when GMA was present could be due to the increase in adsorption rate of poly(vinyl pyrrolidone). The oligomer chains that were rich in GMA were more active for adsorbing and grafting PVP, compared with the moiety of MMA. An increase in the GMA/MMA ratio also leaded to a decrease in epoxy‐group density on the particle surface, since the reactivity of GMA was greater than that of MMA. Results of this work suggest that the influence of GMA/MMA mass ratio on the particle size and surface functionality of the nonporous particles was very significant. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1457–1463, 1999     

Magnetic poly(glycidyl methacrylate) microspheres prepared by dispersion polymerization in the presence of electrostatically stabilized ferrofluids

Fine magnetite nanoparticles, both electrostatically stabilized and nonstabilized, were synthesized in situ by precipitation of Fe(II) and Fe(III) salts in alkaline medium. Magnetic poly(glycidyl methacrylate) (PGMA) microspheres with core‐shell structure, where Fe₃O₄ is the magnetic core and PGMA is the shell, were obtained by dispersion polymerization initiated with 2,2′‐azobisisobutyronitrile (AIBN), 4,4′‐azobis(4‐cyanovaleric acid) (ACVA), or ammonium persulfate (APS) in ethanol containing poly(vinylpyrrolidone) or ethylcellulose stabilizer in the presence of iron oxide ferrofluid. The average microsphere size ranged from 100 nm to 2 μm. The effects of the nature of ferrofluid, polymerization temperature, monomer, initiator, and stabilizer concentration on the PGMA particle size and polydispersity were studied. The particles contained 2–24 wt % of iron. AIBN produced larger microspheres than APS or ACVA. Polymers encapsulating electrostatically stabilized iron oxide particles contained lower amounts of oxirane groups compared with those obtained with untreated ferrofluid. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5827–5837, 2004     

乙酸乙酯/乙醇混合溶液中分散聚合制备单分散亚微米级聚丙烯酰胺微球

以乙酸乙酯/乙醇混合溶液为分散介质, PVP为分散剂, 通过分散聚合法合成了单分散亚微米级PAM微球. 在反应初期, 自动加速现象明显. 由于凝胶效应的影响, 分子量随着单体转化率的提高而逐渐增大. 考察了分散剂浓度对最终产物增率的影响, 并用IR光谱对产物的结构进行了表征, 证明分散聚合体系中吸附稳定机理和接枝稳定机理同时存在, 且以后者为主. 同时还研究了混合溶剂比例、分散剂浓度、初始单体浓度和引发剂浓度对微球粒径及粒径分布的影响. 结果表明, 乙酸乙酯/乙醇体积比在5∶5-7∶3范围内, 可得到粒径在200 nm左右, 且分布较窄的PAM微球; 分散剂浓度增大, 粒径减小; 引发剂浓度增加, 粒径增大; 初始单体浓度较高或较低时, 都得不到单分散性微球.     

Kinetics of dispersion polymerization: Effect of medium composition

The effect of the medium composition (monomer and solvent) on the kinetics of dispersion polymerization of methyl methacrylate (MMA) was studied via reaction calorimetry. It was found that increasing the monomer concentration increased the reaction rate; the exponent of the dependency of the initial reaction rate on the MMA concentration was found to be 0.93. Narrow particle size distributions were achieved at the lower monomer concentrations (0.24–0.81 mol/L) and a minimum size (2.45 μm) was found at an intermediate concentration (0.44 mol/L). The average molecular weight of the PMMA increased and the molecular weight distribution broadened with increasing monomer concentration. During a dispersion polymerization, the MMA concentration was found to decrease linearly with conversion in both phases, whereas the ratio of concentrations in the particles and continuous phase ([M]_p/[M]_c) remained constant (0.47) with partitioning favoring the continuous phase. The average number of free radicals per particle in MMA dispersion polymerization was estimated to be high from the nucleation stage onward (>5000). The increasing rate during the first ～ 40% conversion was primarily caused by the increasing volume of the polymer particle phase. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3638–3647, 2008     

Dispersion copolymerization of styrene and glycidyl methacrylate in polar solvents

Monodispersed copolymer microspheres consisting of styrene and glycidyl methacrylate have been prepared by dispersion polymerization. The effects of various polymerization parameters on the particle size and size distribution were systematically investigated. The initial solubility parameter of the system had a significant effect on the final particle size and size distribution. With decreasing initial solubility parameter, the particle size increased and the size distribution broadened. The particle size decreased with increasing stabilizer concentration, the amount of styrene in the monomer mixture, and decreasing initiator concentration. Received: 30 September 1998 Accepted in revised form: 10 December 1998     

Dispersion polymerization of methyl methacrylate: Mechanism of particle formation

The mechanism for the formation of micron-size polymer particles in the dispersion polymerization of methyl methacrylate was investigated by applying dynamic light scattering to monitor the evolution of the average particle size in the early stages of the polymerization. In addition, the contributions of physically adsorbed stabilizer and graft copolymer were evaluated by measuring the bound, unbound (adsorbed), and free stabilizer, and by determining the amount of added stabilizer required in seeded dispersion polymerizations. Twenty nanometer particles (termed nuclei) were the smallest particles detected and are considered to be formed by aggregation of growing polymer chains precipitating from solution as they exceed their critical chain length. Aggregation of these nuclei with themselves and their aggregates continues until mature and stable particles are formed. This occurs when sufficient stabilizer occupies the particle surface which includes both the polymeric stabilizer [poly(vinylpyrrolidone)] and its graft copolymer which is created in situ. The effects of process variables are discussed based on this mechanistic picture of the dispersion polymerization process. © 1994 John Wiley & Sons, Inc.     

Effect of reaction parameters on the particle size in the dispersion polymerization of 2-hydroxyethyl methacrylate

Poly(2-hydroxyethyl methacrylate) particles in the micron size range were obtained by the dispersion polymerization. Cellulose acetate butyrate and dibenzoyl peroxide were used as steric stabilizer and initiator, respectively. The ultimate particle size could be adjusted by the selection of a suitable polymerization medium consisting of an alcohol added to toluene and by varying their relative amounts. The particle size increased with increasing solubility parameter of the mixture, i.e., by decreasing the toluene/2-methylpropan-1-ol, toluene/butan-2-ol, and toluene/3-methylbutan-1-ol ratio. The particle size decreased with increasing concentration of the stabilizer and/or initiator. At the same time, the particle size distribution became narrower. Particles prepared from polymerization mixtures purged with nitrogen before the start of polymerization were smaller, and of narrower distribution, than those prepared from nitrogen-non-purged mixtures. Equilibrium swelling of particles in toluene decreased with the decreasing content of toluene in the polymerization mixture. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3785–3792, 1999     

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.     

Heterogeneous polymerization with polyaspartate macromonomer having vinyl pendant groups. II. Control of particle diameter and diameter distribution in dispersion copolymerization

To control particle diameter and particle diameter distribution in dispersion copolymerization of styrene and sodium polyaspartate macromonomer containing vinylbenzyl pendant groups, effects of some polymerization parameters, water contents, initiator concentration, styrene monomer concentration, reaction temperature, and type of initiator on the particle diameter and the diameter distribution were investigated. Variation of the water contents from 20 to 80 vol % controls the resultant particle diameter from 0.066 to 0.47 μm. The diameter increased with increasing initiator concentration. This tendency is similar to dispersion polymerization system using a nonpolymerizable stabilizer. Particle diameter distribution broadened with increasing styrene monomer concentration. This trend was attributed to the increase of a period of particle formation. This result indicated that the period of particle formation affected the resultant particle diameter distribution. Particle diameter distribution was successfully improved (CV = 9.1 from 23.6%) by shortening of decomposition time of initiator. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2281–2288, 2009     

Emulsion copolymerization of styrene and methacrylic acid in the presence of a polyethylene oxide based-polymerizable stabilizer with a shorter chain length

The emulsion copolymerization of styrene and methacrylic acid (MAA) was performed in the presence of a relatively new macromonomer, poly(ethylene glycol) ethyl ether methacrylate (PEG-EEM) as a stabilizer. In contrast to similar studies, a macromonomer having relatively shorter polyethylene oxide chain length (i.e., M_n:246, n ≈ 3.0) was selected for this study. Highly uniform and carboxyl functionalized latex particles in the size range of 0.16–0.50 μm were obtained by changing MAA, PEG-EEM, total monomer, and initiator concentrations. The use of PEG-EEM as a stabilizer resulted in larger monodisperse particles relative to those obtained by the emulsifier-free emulsion copolymerization of styrene and MAA. The particle size decreased and the polymerization rate increased with the increasing MAA feed concentration. The application of power law model indicated that MAA concentration was more effective in the presence of PEG-EEM for control of particle size relative to similar systems. The latex particles with higher numbers of surface-carboxyl groups were obtained with the higher MAA feed concentrations. Although the particle size decreased and the polymerization rate increased with the increasing PEG-EEM concentration in the emulsion polymerization of styrene, both of them remained roughly constant with the increasing PEG-EEM concentration in the presence of MAA. Received: 21 December 2000 Accepted: 13 July 2000     

Semibatch emulsion polymerization of methyl methacrylate using different polyurethane particles

Aqueous acrylic‐polyurethane (AC–PU) hybrid emulsions were prepared by semibatch emulsion polymerization of methyl methacrylate (MMA) in the presence of four polyurethane (PU) dispersions. The PU dispersions were synthesized with isophorone diisocyanate (IPDI), 1000 and 2000 molecular weight (MW) poly(neopentyl) adipate, 1000 MW polytetramethyleneetherglycol, butanediol (BD), and dimethylol propionic acid (DMPA). MMA was added in the monomer emulsion feed. We studied the effect of the use of different PU seed particles on the rate of polymerization, the particle size and distribution, the number of particles, and the average number of radicals per particle. The PU rigidity was controlled by varying the polyol chemical structure, the polyol MW (M_n), and by adding BD. The monomer feed rate was varied to study its influence on the process. It was observed that the PU particles that had been prepared with a higher MW polyol swelled better with MMA before the monomer‐starved conditions occurred. There seemed to be no significant discrepancies between the series with different PU seeds in the monomer‐starved conditions. The overall conversion depended on the monomer addition rate, and the polymerization rate acquired a constant value that was comparable to the value of the monomer addition rate. The instantaneous conversion increased slightly. The average particle size increased, and the total particle number in the reactor was constant and similar to the number of PU particles in the initial charge. The average number of radicals per particle increased. The differences between the system with a constant particle number and average number of radicals per particle and the system with a fixed radical concentration are discussed. The semibatch emulsion polymerization of MMA in the presence of PU particles studied was better compared to the system with a fixed radical concentration. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 844–858, 2005     

分散共聚法制备窄分布P(St-co-nBA)微球

用分散共聚法制得窄分布苯乙烯(St)和丙烯酸正丁酯(nBA)的共聚物微球.采用1H-NMR、DSC、FTIR、SEM、LS等对共聚物的结构、形态、性能进行表征,考察了初始单体配比、温度、稳定剂浓度、分散介质极性、引发剂对微球粒径、粒径分布及转化率的影响.实验结果表明,初始单体比nBA/St增大,微球粒径增大,分布变宽,...