Highly monodisperse crosslinked polymethylmethacrylate microparticles by dispersion polymerization

Highly monodisperse polymethylmethacrylate (PMMA) microparticles crosslinked with carboxylic group-containing urethane acrylates (CUA) were produced by simple dispersion polymerization in methanol solution. In contrast to conventional crosslinkers, the CUA employed as a crosslinker was excellent for maintaining the monodispersity of PMMA microparticles even at moderate crosslinker concentrations (to about 5 wt%). It was believed that the CUA helped form the monomer-swellable surface of primary particles, because of the structurally long tetramethylene oxide groups in the molecule. Carboxylic groups in the molecular backbone resulted in larger primary particles by increasing the solubility of the monomer mixture in the medium. Owing to these larger primary particles, the crosslinked PMMA particles showed lower polymerization rates than the linear ones during particle growth. However, at high CUA concentrations (about 10 wt%), bimodal distributions were observed. This was attributed to the high crosslinking density of the primary particle surfaces. Therefore, monomer diffusion toward the polymer phase was restricted, resulting in more favorable secondary nucleation in the medium. Received: 12 May 1998 Accepted: 19 August 1998     

Effect of crosslinking on porous poly(methyl methacrylate) produced by phase separation

Porous polymethyl methacrylate scaffolds were produced by phase separation during polymerisation in solution, using ethanol as solvent, with monomer/ethanol weight ratios from 80/20 up to 20/80 and different ethylenglycol dimethacrylate contents (1, 5 and 10 wt%) as crosslinker agent. For ethanol weight ratios equal to or lower than 50 wt%, the material presents a homogeneous distribution of dispersed pores. For higher ethanol contents, a highly interconnected porous structure is obtained. The transition from one type of morphology to the other can be also controlled with the amount of crosslinker added in the reactive mixture. Bulk polymethyl methacrylate samples (non-porous) with the same crosslinking densities were also synthesised as reference. The effect of crosslinker is studied by porosity measurements, scanning electron microscopy, dynamic-mechanical spectroscopy and differential scanning calorimetry.     

AIBN/SmCl3/乳酸体系催化甲基丙烯酸甲酯的反向原子转移自由基聚合

利用稀土金属化合物三氯化钐(SmCl3)和二氯化钐(SmCl2)之间的单电子转移反应,以AIBN/SmCl3/乳酸作为反向原子转移自由基聚合(ReverseATRP)的催化体系,成功地实现了甲基丙烯酸甲酯(MMA)的反向ATRP,并考察了温度、溶剂和组分比对聚合反应的影响.MMA在该体系中的聚合反应是一级反应,所得PMMA的分子量与单体转化率成正比,聚合物的分子量分布较窄(Mw/Mn<1.5),具有活性聚合的特征.     

相互缠结的聚甲基丙烯酸甲酯/磺化聚苯乙烯复合水基微乳液Ⅰ:制备及影响因素

将聚苯乙烯制成磺化聚苯乙烯离聚体 (SPS) ,利用相反转技术 ,将磺化聚苯乙烯离聚体加水制成具有纳米级的稳定的水基微乳液。利用SPS纳米微粒核内部作为反应场所 ,用引发剂引发亲油性单体甲基丙烯酸甲酯聚合 ,制备具有相互缠结结构的PMMA/SPS复合水基微乳液。研究了引发剂的用量、MMA的用量、溶剂极性对聚合反应及复合水基微乳液的影响     

One-step preparation of highly monodisperse micron-size particles in organic solvents

In this communication, we report the first simple and fast one-step method for synthesizing highly monodisperse micron-size PMMA particles in organic media through dispersion polymerization in the presence of PHSA (a polyhydroxyl-stearic-acid graft PMMA copolymer) as a stabilizer. There are two significant advantages of our method over earlier methods. First, by optimizing the composition of a solvent mixture of hexane and dodecane, we were able to increase the concentration of monomer up to 50-56% and obtain unusually large (up to 10 mum in diameter) PMMA particles. Second, by strictly controlling the nucleation time, we were able to make PMMA particles with a low polydispersity of around 1%, much lower than has ever before been achieved for such large particles. We also report an unusual apparent metastable state in the nucleation stage.     

N,N-二乙基硫代氨基甲酰硫基团(S_2CNEt_2)为假卤原子转移的原子转移自由基聚合新体系

综述了原子转移自由基聚合 (ATRP)中 ,以N ,N 二乙基硫代氨基甲酰硫基团 (S2 CNEt2 )转移实现活性聚合、控制聚合物结构的 4种新方法 :非卤化物 ,N ,N 二乙基二硫代氨基甲酸亚铜 [Cu(S2 CNEt2 ) ]催化甲基丙烯酸甲酯 (MMA)的正向ATRP ;2 ,2′ 联吡啶存在的条件下 ,过氧化苯甲酰 (BPO)与Cu(S2 CNEt2 )的氧化还原反应控制MMA的本体反向ATRP;同时含可转移卤原子、基团的氯化二乙基二硫代氨基甲酸铜 [Cu(S2 CNEt2 ) Cl]成功地用于偶氮二异丁腈或BPO引发的乙烯类单体反向ATRP.假卤原子S2 CNEt2 转移的ATRP得到窄分布的精确结构聚合物分子链ω 端含有光敏基团S2 CNEt2 ,可引发乙烯类单体的常温光聚合 ,实现ATRP与光聚合相结合制备嵌段共聚物     

ATRP of MMA initiated by 2-bromomethyl-4,5-diphenyloxazole at room temperature and study of fluorescent property

Atom transfer radical polymerization (ATRP) of MMA was conducted successfully at ambient temperature (25 °C) using 2-bromomethyl-4,5-diphenyloxazole as initiator, CuBr/2,2′-bipyridine (BPY) as catalyst, and 1,4-Dioxane as solvent. Factors such as the reaction temperature, mole ratio of monomer and catalyst to initiator, solvent and so on, which can affect the ATRP system, were discussed in the paper. Chain extension was conducted using polymer as the macro-initiator which was characterized via ¹H NMR. The optical property of initiator was well preserved in the obtained PMMA, and the end-functionalized PMMA exhibited obvious fluorescent emission at 367 nm.     

无皂乳液聚合法制备聚甲基丙烯酸甲酯包覆厚度可控的纳米核-壳二氧化硅微球

用改进的Stöber法和无皂乳液聚合法制备窄分布的二氧化硅/PMMA核-壳纳米微球. 用改进的Stöber法将3-乙氧基甲基丙烯酸丙基硅烷(MPS)修饰在纳米的二氧化硅表面后, 用无皂乳液聚合法制备核-壳纳米微球. 该法简单有效且得到厚度均匀的聚合物包覆层. 随着单体MMA用量的增加, 用动态光散射法测量, PMMA壳层的厚度从6.4 nm增加到96.3 nm. 热重分析表明, PMMA的含量从22.25%增加到93.41%. 扫描电子显微镜和透射电子显微镜结果表明, 得到的是包覆良好、表面光滑的核-壳无机/聚合物纳米微球.     

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.     

Seed Dispersion Polymerization to Micron-Size Monodisperse Polymer Particles

Abstract

Seed dispersion polymerization of methyl methacrylate (MMA) in the presence of monodisperse PMMA particles was carried out in an aqueous methanol using poly(methacrylic acid) stabilizer. The polymerization using 2. 5 μ. m-sized seed particles gave monodisperse PMMA particles in the diameter up to 4. 9 μm. The solvent composition and monomer concentration greatly affected the polymerization behavior. Under appropriate conditions, monodisperse PMMA particles in the diameter up to 8. 9 μ, m was prepared from 4. 6 μm-sized seed particles. The seed dispersion polymerization of styrene in the presence of the seed particles produced monodisperse PMMA-polystyrene particles in the micron range. The particles were supposed to have a structure consisting of PMMA-core and polystyrene-shell from ESCA analysis.     

Emulsion polymerization of styrene and methyl methacrylate using a hydrophobically modified inulin and comparison with other surfactants

The use of a new class of graft polymer surfactants, based on inulin, in emulsion polymerization of poly(methyl methacrylate) (PMMA) and polystyrene (PS) particles is described. PS and PMMA were synthesized by emulsion polymerization, and stable particles with a high monomer content (50 wt %) were obtained with a very small amount of polymeric surfactant ([surfactant]/[monomer] = 0.0033). The latex dispersions were characterized by dynamic light scattering and by transmission electron microscopy to obtain the average particle size and the polydispersity index, and the stability was determined by turbidimetry measurements and expressed in terms of critical coagulation concentration. The last section gives a comparison of PMMA particles prepared by emulsion polymerization using classical surfactants from different types as emulsifiers with that obtained using the copolymer surfactant. It shows the superiority of INUTEC SP1 as it is the only one that allows stable particles at 20 wt % monomer content, with a smaller ratio [surfactant]/[monomer] = 0.002.     

Highly crosslinked micron-range polymer microspheres by dispersion polymerization of divinylbenzene

Narrow disperse microparticles are formed by dispersion polymerization of commercial divinylbenzene in acetonitrile or ethanol solution in the presence of 2,2′-azobis(2-methylpropionitrile) initiator and polyvinylpyrrolidone stabilizer. The particles have average diameters between 1 and 9 μm depending on monomer concentration, solvent, and temperature. While the smaller particles are relatively smooth, surface texture increases with diameter to give popcorn shapes at 9 μm diameter. High crosslinker concentration is shown to be essential for particle formation. © 1993 John Wiley & Sons, Inc.     

Effect of the reaction parameters on the particle size in the dispersion polymerization of 2‐hydroxyethyl and glycidyl methacrylate in the presence of a ferrofluid

The precipitation of Fe₃O₄ from an aqueous solution with ammonium hydroxide produced nanoparticles that were coated with a layer of oleic acid [or, in some cases, poly(ethylene oxide) or poly(vinylpyrrolidone)] before their dispersion into the organic phase. The encapsulation of magnetite nanoparticles in poly(2‐hydroxyethyl methacrylate) or poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) microparticles was achieved by dispersion polymerization in toluene/2‐methylpropan‐1‐ol. Magnetic poly(glycidyl methacrylate) microparticles were obtained in the presence of poly(ethylene oxide) at the magnetite/monomer interface. The particles containing up to 20 wt % iron maintained their discrete nature and did not aggregate. The effect of the reaction medium polarity, the concentrations of the monomer, initiator, and stabilizer, and the temperature on the particle size, particle size distribution, and iron and oxirane group contents was studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1848–1863, 2003     

分散聚合与水热处理相结合制备单分散聚苯乙烯微球的研究

将分散聚合与水热处理相结合,以聚乙烯醇为稳定剂,以乙醇和水为分散介质,三羟甲基丙烷三丙烯酸酯为交联剂,一步法成功制备得到不同粒径的单分散交联聚苯乙烯微球.以乙醇/水的比例为50/50的反应体系为基础,研究了聚乙烯醇类型和含量,有机相含量,引发剂浓度,以及水热釜填充量等对所制备的微球形貌的影响,发现聚乙烯醇类稳定剂的分子量的降低和含量的增多倾向于生成黏连的微球;在有交联剂的条件下,不含稳定剂的体系仍能够得到单分散的交联PS微球;有机相含量的增加会导致微球呈现多分散性;而体系中引发剂的含量和反应液在水热釜中的填充量对微球的形貌影响不大.进一步针对水热法的特点分析探讨了一步法成功制备单分散的交联聚苯乙烯微球的原因及其机理.     

Effects of Ionic Liquid [Me3NC2H4OH]+[ZnCl3]− on γ‐Radiation Polymerization of Methyl Methacrylate in Ethanol and N,N‐Dimethylformamide

Summary: Radiation‐induced polymerization of methyl methacrylate (MMA) in ethanol (EtOH) and N,N‐dimethylformamide (DMF) in the presence of ionic liquid [Me₃NC₂H₄OH]⁺[ZnCl₃]⁻ is reported. A substantial increase in monomer conversion and molecular weight is observed at room‐temperature ionic liquid (RTIL) >60 vol.‐%, and the resulting PMMA has a broad multimodal MWD. A clear difference in the MWD pattern is noted between EtOH/RTIL and DMF/RTIL systems, probably due to the complicated interactions between the solvent and ionic liquid.

Gel permeation chromatography traces of poly(methyl methacrylate) obtained by radiation polymerization in EtOH/RTIL and DMF/RTIL mixed solvent. Organic/RTIL (v/v): 1) 100:0; 2) 80:20; 3) 60:40; 4); 40:60; 5) 0:100.     

Production of micron-sized monodispersed core/shell composite polymer particles by seeded dispersion polymerization

 The effect of the weight ratio of seed polymer/monomer on the morphology of the poly(methyl methacrylate) (PMMA)/polystyrene (PS) monodispersed composite particles produced by batch seeded dispersion polymerization of styrene with 1.64-μm-sized monodispersed PMMA seed particles in a methanol/water medium (4/1 w/w) was examined. In the PMMA/PS weight ratios of 3/1 and 2/1, the composite particles had a clear morphology consisting of a PMMA core and a PS shell. In the ratio of 1/1, a lot of small PS domains were observed in the PMMA core though the PS shell was still formed. By stepwise addition of styrene monomer, the formation of the small PS domain was depressed and complete core/shell morphology was formed. Absorption/release treatments of toluene into/from the PMMA/PS (1/1 w/w) composite particles resulted in a drastic morphological change from the core/shell structure to a multi- layered one. Received: 2 February 1999 Accepted in revised form: 7 April     

CuX2络合物催化甲基丙烯酸甲酯的氧化聚合

研究了高氧化态过渡金属卤化物络合物催化甲基丙烯酸甲酯(MMA)的氧化聚合.首先在叔胺类聚合物存在条件下以CuBr2/2,2′-联吡啶(bPy)络合物催化MMA在不同溶剂中的氧化聚合,结果在环己酮中得到PMMA均聚物,CuBr2/bPy同叔胺的氧化还原引发可以忽略.随后在环己酮中分别以不同络合物催化MMA的氧化聚合.结果...     

Synthesis of PMMA‐b‐PBA block copolymer in homogeneous and miniemulsion systems by DPE controlled radical polymerization

In this research, poly(methyl methacrylate)‐b‐poly(butyl acrylate) (PMMA‐b‐PBA) block copolymers were prepared by 1,1‐diphenylethene (DPE) controlled radical polymerization in homogeneous and miniemulsion systems. First, monomer methyl methacrylate (MMA), initiator 2,2′‐azobisisobutyronitrile (AIBN) and a control agent DPE were bulk polymerized to form the DPE‐containing PMMA macroinitiator. Then the DPE‐containing PMMA was heated in the presence of a second monomer BA, the block copolymer was synthesized successfully. The effects of solvent and polymerization methods (homogeneous polymerization or miniemulsion polymerization) on the reaction rate, controlled living character, molecular weight (M_n) and molecular weight distribution (PDI) of polymers throughout the polymerization were studied and discussed. The results showed that, increasing the amounts of solvent reduced the reaction rate and viscosity of the polymerization system. It allowed more activation–deactivation cycles to occur at a given conversion thus better controlled living character and narrower molecular weight distribution of polymers were demonstrated throughout the polymerization. Furthermore, the polymerization carried out in miniemulsion system exhibited higher reaction rate and better controlled living character than those in homogeneous system. It was attributed to the compartmentalization of growing radicals and the enhanced deactivation reaction of DPE controlled radical polymerization in miniemulsified droplets. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4435–4445, 2009     

Tacticity control in the radical polymerization of 2,2,2-trifluoroethyl methacrylate with fluoroalcohol

The free-radical polymerization of 2,2,2-trifluoroethyl methacrylate (TEMA) was carried out in fluoroalcohols to achieve stereoregulation. The polymerization reactivity at low temperature and syndiotactic specificity were enhanced by the use of fluoroalcohol as a solvent. The polymer having triad syndiotacticity (rr) of 70% was obtained in perfluoro-t-butyl alcohol. It was noted that the stereochemistry was nearly independent of reaction temperature. The stereoeffect of fluoroalcohols seemed to be due to the hydrogen-bonding interaction between the alcohol and the monomer or growing species. The hydrogen-bonding formation was determined by FTIR. The copolymerization of TEMA with methyl methacrylate (MMA) in hexafluoroisopropanol afforded a copolymer with syndiotactic specificity. By this method, a cladding material for an optical fiber based on poly(methyl methacrylate) (PMMA) with high mechanical strength and low refractive index could be obtained.     

PMMA/MMT nanocomposites prepared by one-step in situ intercalative solution polymerization

Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by one-step in situ intercalative solution polymerization involving simultaneous modification of MMT with quaternary ammonium salts (QAS), polymerization and polymer intercalation. Polymerization proceeded at 70 °C in a mixture of ethanol and water, whereas the nanocomposite was precipitated with only water. Four QAS’s with different alkyl chain lengths, as well as a QAS with an additional acrylic group, were used to study the influence of the type of quaternary ammonium salt on intercalation. The largest extent of intercalation was achieved in nanocomposites with the QAS having one long alkyl (C16) chain. The obtained PMMA/MMT intercalated nanocomposites exhibited a higher glass transition temperature, better thermal stability, and improved solvent resistance than the pure PMMA.