Preparation of poly(vinyl acetate) microspheres with narrow particle size distributions by low temperature suspension polymerization of vinyl acetate

To estimate influences of suspension polymerization conditions including conversion, polymerization temperature, stirring rate, initiator concentration, monomer concentration, and suspending agent concentration on the volume average diameter (D_avg) and particle size distribution (PSD) of poly(vinyl acetate) (PVAc) microspheres, vinyl acetate (VAc) was suspension‐polymerized at low temperature using 2,2′‐azobis(2,4‐dimethylvaleronitrile) as an initiator. The effects of each condition, on D_avg of PVAc microspheres, were expressed as follows, D_avg = [conversion]^a[temperature]^b[rpm]^c[ADMVN]^d[VAc]^f [suspending agent]^g. Logarithms of D_avg were linearly proportional to those of polymerization conditions, and their exponents, a, b, c, d, f, and g were calculated as 0.27, ?13.7, ?1.37, ?0.21, 0.58, and 0.29, respectively. Variations of PSDs, according to polymerization conditions, were examined by considering polymerization rate, droplet or suspension viscosity, and droplet break‐up/coagulation equilibrium. From these results, PVAc microspheres with various sizes and narrow PSDs were obtained effectively under carefully controlled polymerization conditions, which can be used as promising precursors of novel PVA microspheres through heterogeneous surface saponification. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4064–4070, 2006     

原位乳液聚合法制备PVAc-OMMT纳米复合材料的性能研究

通过乳液聚合技术引发醋酸乙烯酯（VAc）在有机插层剂改性的蒙脱土（OMMT）中原位插层聚合,制备了一种新型聚合物-黏土纳米复合材料PVAc-OMMT。利用X射线衍射、透射电子显微镜和红外光谱研究了复合材料的结构和微观形态;利用热失重分析、差示扫描量热法研究了不同OMMT用量的复合材料的热稳定性;同时探讨了OMMT用量对材料力学性能的影响。结果表明,采用该方法得到了插层型纳米复合材料,且该纳米复合材料与相同条件下制备的纯聚醋酸乙烯酯（PVAc）相比,具有较高的玻璃化转变温度、优良的热稳定性和较好的力学性能;随着OMMT用量的增加,材料的起始热分解温度逐渐向高温方向移动,热稳定性提高;材料的拉伸强度随OMMT用量的增加出现先增加后减小的趋势,当OMMT用量为10 %（质量分数,下同）时,材料的拉伸强度达到最大值7.87 MPa。     

悬浮聚合法制备聚甲基丙烯酸甲酯微球的研究

以明胶为稳定剂采用悬浮聚合法合成了微米级聚甲基丙烯酸甲酯微球。通过研究搅拌速度、聚合温度及稳定剂用量,确定了较理想的合成工艺条件。     

低聚合度、低醇解度聚乙烯醇的合成与性能研究——I.低聚合度聚醋酸乙烯酯的合成

以甲醇为溶剂,偶氮二异丁腈(AIBN)为引发剂,采用自由基聚合方法合成了低聚合度聚醋酸乙烯酯,并对其结构进行了表征。讨论了聚合时间、引发剂用量、物料配比、聚合温度等因素对聚合率的影响,获得了相对较佳的工艺参数。     

Preparation and Properties of Thermoplastic Expandable Microspheres With P(VDC-AN-MMA) Shell by Suspension Polymerization

Thermoplastic expandable microspheres (TEMs) having core/shell structure were prepared via suspension polymerization with vinylidene chloride (VDC), acrylonitrile (AN), and methyl methacrylate (MMA) as monomers and i-butane as blowing agent. TEMs were about 20 µm in diameter and had a hollow core containing i-butane. The influence of the monomer feed ratio and blowing agent content was researched. When the monomers composition of 58.4 wt% VDC, 28 wt% AN, 13.6 wt% MMA, and 32 wt% i-butane in oil phase, suspension polymerization could yield TEMs having good expansion properties. The maximum expansion volume was 25 times of original volume at about 111–120°C, the blowing agent content in microspheres was about 21.5 wt%. The T_m.e, T_o.e, and T_o.s. of the TEMs increased with the VDC content in the polymerizable monomers decreasing.     

悬浮聚合聚甲基丙烯酸甲酯／蒙脱土纳米复合材料的制备及表征

采用悬浮聚合法制备了聚甲基丙烯酸甲酯／蒙脱土（PMMA/MMT）纳米复合材料，利用X射线衍射仪、透射电子显微镜和傅里叶变换红外光谱等手段表征了复合材料的结构，研究了不同改性剂对复合材料结构的影响。通过热重分析考察了复合材料的热性能。结果表明，通过悬浮聚合可以成功制备剥离型纳米复合材料，PMMA基体与MMT可以产生较强的相互作用。MMT的加入可以显著提高复合材料的热稳定性。当MMT含量为10％（质量分数，下同）时，PMMA的最大分解温度提高了15℃。     

Preparation of Glutathione Molecularly Imprinted Polymer Microspheres by Reversed Phase Suspension Polymerization

Molecularly imprinted polymer microspheres (MIPMs) for Glutathione had been prepared by the reversed phase suspension polymerization method; MIPMs were synthesized by using acrylamide and N-vinyl pyrrolidone as functional monomers. N,N’-methylenebisacrylamide and dimethyl diallyl ammonium chloride were the cross-linkers and H₂O₂ and Vc were redox initiators, Span-80 was the surfactant used and cyclohexane was the oil phase. Our work can provide a method to obtain ball MIPMs, and in this way, the destruction of acting sites because powdery MIPMs could be avoided. Moreover, the low concentration of cross-linker results in imprinted sites not being formed during the reversed phase suspension polymerization. The double cross-linkers not only solved this problem, but they also enlarged the selection range of the template, monomer and cross-linker. Simultaneously, there’s obviously a significant amount of synergy between the two cross-linkers that perhaps improve the adsorption capacity and selectivity. The conditions were investigated and optimized, and the optimum conditions were obtained as follows: the ratio of n_AM/n_NVP was 2; the optimum temperature and time were 50°C and 4.5 h; and, the dosage of GSH, DMDAAC and Vc were 0.8 g, 14 g and 0.023 g, respectively, under the optimum conditions, GSH-MIPM was prepared and showed the adsorption capacity was 75 mg · g^?1. Also, based on the samples prepared at the starting process and under optimal conditions, the adsorption kinetics and adsorption isotherm were investigated and analyzed, respectively.     

A Novel Approach to Prepare Poly(Vinyl Acetate)/Ag Nanocomposite for Effective Antimicrobial Coating Applications

Polyvinyl acetate nanocomposites were successfully prepared based on silver nanoparticles. First, silver nanoparticles were directly prepared during the in situ emulsion polymerization of vinyl acetate monomer using AgNO₃ as a source of Ag⁺ ions and poly(vinyl alcohol) was used for dual functions as emulsifier for emulsion polymerization and as a stabilizing agent, trisodium citrate (C₆H₅O₇Na₃) was used as reducing agent for Ag⁺ ions during the polymerization process. The prepared polyvinyl acetate/Ag nanocomposites were assessed using X-ray diffraction, scanning electron microscopy, Fourier transform infrared, transmission electron microscopy, and ultraviolet spectra. The antibacterial properties of the prepared polyvinyl acetate/Ag nanocomposites were investigated as antimicrobial activity against pathogenic bacteria, i.e., Staphylococcus aureus (G^+ve bacteria) and Escherichia coli (G^?ve bacteria). These polyvinyl acetate nanocomposites could be used as a promising material for enhanced and continuous antibacterial applications as coating and packaging materials.     

反相悬浮聚合法制备腐殖酸高吸水性树脂进展

反相悬浮聚合法制备腐殖酸-聚丙烯酸高吸水性树脂(HA-PAA),论述了高吸水性树脂的结构及复合机理,阐明了高吸水性树脂的应用领域。腐植酸树脂具有良好的吸附、吸水、降滤失和抗温、抗盐性能,得到了广泛的应用。随着腐植酸树脂研究的进展,其应用前景将更加广阔。     

微孔膜乳化与悬浮聚合结合法制备均一PST-DVB多孔微球

使用自制的微孔膜乳化装置,通过微孔膜乳化结合悬浮聚合方法,批量制备了微米级的聚(苯乙烯-二乙烯基苯)(PST-DVB)微球. 实验中采用孔径为5.2 mm的微孔膜,考察了膜线剪切力、管线速度和膜乳化压力对微球粒径及其分布的影响,以及膜乳化压力和膜线剪切力对分散相流速的影响. 研究结果表明,膜线剪切力在合适的范围内对微球粒径影响不大,而管线速度在14.38~26.49 m/min之间、膜乳化压力在0.008~0.012 MPa之间时,所制备微球的尺寸均一. 研究还发现膜乳化压力是影响分散相流速的最主要因素. 研究结果为装置的规模化放大奠定了理论基础.     

反相微乳液法制备磁性分子印迹聚合物微球

以二氯苯酚为模板分子、丙烯酰胺(AM)为功能单体、三羟甲基丙烷三丙烯酸酯(TRIM)为交联单体、Fe3O4为磁性组分,采用反相微乳液悬浮聚合法制备了磁性分子印迹聚合物微球(MMIPMs)。研究了吸附时间、温度、pH对吸附性能的影响,并考察了其重复利用性。结果表明,温度对二氯苯酚-MMIPMs吸附性能影响不大。底物溶液pH对MMIPMs的吸附性能有一定影响,吸附量随pH的升高而增大,当pH为7.0时,吸附量最大。MMIPMs具有良好的重复利用率。     

静态反相悬浮聚合法合成聚丙烯酸钠

以过氧化氢为引发剂,以食用植物油如菜子油、花生油、茶油、葵花油、大豆油或者玉米油为分散相,采用静态反相悬浮聚合工艺合成聚丙烯酸钠,研究了引发剂用量、分散相以及反应温度对聚丙烯酸钠分子量的影响。结果表明,随过氧化氢浓度增大、丙烯酸钠单体浓度降低、聚丙烯酸钠的分子量降低;玉米油为分散相时聚丙烯酸钠的分子量最大;随反应温度升高,聚丙烯酸钠的分子量增大;但反应温度超过60℃时,聚丙烯酸钠的分子量随反应温度升高而降低。     

悬浮聚合法制备磁性微球的粒度分布特性

本文研究了含有微细铁黑颗粒的混合单体悬浮聚合产物的粒度分布特性。分析了分散剂、超声预分散和无机铁黑颗粒对形成粒度多峰分布的影响。结果表明,分散剂是体系中形成小颗粒的主要因素;超声波的预分散作用使悬浮体系的液滴破裂以“腐蚀破碎（erosive breakage)”为主;无机铁黑颗粒由于其表面亲水性,倾向于分布在油性单体液表面,不仅有利于悬浮液滴的“磨蚀破碎”,同时也对分散液滴具有良好的稳定作用。上述因素的共同作用使得聚合产物的粒度呈三峰分布。     

苯乙烯/纳米无机粒子原位悬浮聚合制备EPS纳米复合材料

采用自由基原位悬浮聚合方法,由苯乙烯/纳米无机粒子(NIP)聚合制备聚苯乙烯纳米复合材料(PSNC),再以戊烷为发泡剂制备了可发性聚苯乙烯纳米复合材料(EPSNC),筛选了NIP改性剂的种类。利用凝胶渗透色谱仪和热重分析仪对EPSNC进行表征,研究了EPSNC的分子结构和热性能,采用扫描电子显微镜对EPSNC泡体内部微观形貌进行表征,研究NIP含量对其泡体微观形貌的影响规律。结果表明,以钛酸酯偶联剂改性NIP (M NIP)聚合产率最高;M NIP用量在一定范围内对EPSNC的相对分子质量影响不大,但相对分子质量分布变窄;含有M NIP的EPSNC的热稳定性明显提高;EPSNC发泡时NIP起成核作用,M NIP能够均匀地分散在EPSNC中,其泡孔堆积有序,细密一致,且多为闭孔结构。     

聚合法制备静电复印彩粉的工艺与性能

试验采用特殊悬浮聚合工艺 ,可获得彩色静电复印机用色粉。主要讨论聚合彩粉的荷电性能 ,单体比例、分子量调节剂、剥离剂对聚合彩粉的影响。     

Preparation of Novel Poly(hydroxyethyl methacrylate-coglycidyl methacrylate)-Grafted Core-Shell Magnetic Chitosan Microspheres and Immobilization of Lactase

Poly(hydroxyethyl methacrylate-co-glycidyl methacrylate)-grafted magnetic chitosan microspheres (HG-MCM) were prepared using reversed-phase suspension polymerization method. The HG-MCM presented a core-shell structure and regular spherical shape with poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) grafted onto the chitosan layer coating the Fe₃O₄ cores. The average diameter of the magnetic microspheres was 10.67 μm, within a narrow size distribution of 6.6–17.4 μm. The saturation magnetization and retentivity of the magnetic microspheres were 7.0033 emu/g and 0.6273 emu/g, respectively. The application of HG-MCM in immobilization of lactase showed that the immobilized enzyme presented higher storage, pH and thermal stability compared to the free enzyme. This indicates that HG-MCM have potential applications in bio-macromolecule immobilization.     

Physical Properties of Isotactic Poly(propylene)/Silver Nanocomposites: Dynamic Crystallization Behavior and Resultant Morphology

Summary: The presence of silver nanoparticles (0.01–5 wt.‐%) increased the crystallization temperature of isotactic poly(propylene) (iPP) (e.g., a 5 wt.‐% content increases the temperature by ca. 7 °C) and produced a sharper crystalline peak. It had little effect on the melt rheology of the nanocomposites. The shear‐induced crystallization behavior of iPP was accelerated with increasing Ag content and imposed frequency. In addition, the promoting effect of Ag nanoparticles on the overall crystallization behavior was more notable at 140 °C than at 130 °C. The wide‐angle X‐ray diffraction scans of iPP nanocomposites with 5 wt.‐% Ag crystallized at 130 °C clearly presented another peak at a 2θ value of 15.8°, which corresponded to a β‐form crystal. The nanocomposites with 5 wt.‐% Ag crystallized at 130 °C gave double melting peaks at 154 and 166 °C. On the other hand, the samples crystallized at 140 °C produced two melting peaks at 166 and 172 °C. The introduction of as much as 0.1 wt.‐% of Ag nanoparticles increased both the tensile strength and elongation at break, but subsequent further addition caused a decrease. In addition, iPP nanocomposites with more than 1 wt.‐% Ag exhibited a higher modulus than pure iPP.

Time dependence of G′ of iPP and iPP/Ag nanocomposites at 130 °C at ω = 1 rad · s^?1.     

原位乳液聚合制备的聚丙烯酸丁酯/纳米SiO2复合粒子的形貌和形成机理

通过吸附于水相分散纳米SiO2粒子表面的2,2'-偶氮(2-脒基丙烷)二氢氯化物(AIBA)的引发作用,进行丙烯酸丁酯(BA)的原位乳液聚合,制备聚丙烯酸丁酯(PBA)/纳米SiO2复合乳胶粒.分别采用透射电镜观察复合粒子的形貌,高速离心分离/超声分散和氢氟酸腐蚀表征复合胶乳中PBA乳胶粒与纳米SiO2粒子的结合程度.发现有纳米SiO2粒子聚集于复合乳胶粒表面,复合粒子表面粗糙,呈"草莓形"结构;当复合粒子中SiO2质量分率为14.6%～22.6%时,60%左右的纳米SiO2富集于复合粒子表面,30%左右被包覆在复合粒子内部,另有少量游离于水相.采用原位乳液聚合得到的复合粒子中纳米SiO2与聚合物的结合牢度远大于以AIBA为引发剂合成的PBA乳液与纳米SiO2分散液直接混合所能达到的结合牢度.认为在原位乳液聚合过程中,由于纳米SiO2粒子表面锚固的PBA量的不同,引起SiO2粒子的亲水/亲油性和与PBA的相容性也不相同,导致出现以上的SiO2的分布特性和复合粒子形貌.     

Preparation of high molecular weight poly(vinyl alcohol) with high yield by emulsion polymerization of vinyl acetate using 2,2′‐azobis(2‐amidinopropane) dihydrochloride

To prepare high molecular weight (HMW) poly(vinyl acetate) (PVAc) with high yield and high linearity as a precursor of HMW poly(vinyl alcohol) (PVA), vinyl acetate (VAc) was emulsion polymerized using, azo initiator, 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH). This was compared with the polymerization using potassium peroxodisulfate (KPS) as an initiator at various polymerization conditions. PVA, having a maximum number average degree of polymerization (P_n) of 3500 was obtained by the saponification of PVAc with P_n of 13,000–14,000, degree of branching (DB) for the acetyl group of about 3.4–3.5, and a maximum conversion of VAc into PVAc of 95%, which was polymerized by AAPH. These numerical values were superior compared with 14,500–15,000 of P_n of PVAc, obtained by KPS, and 3100 of maximum P_n of resulting PVA, DB of about 3.7–3.8, and maximum conversion of 90%. From the foregoing experimental results, we found that AAPH was a more efficient initiator than KPS in increasing both conversion of PVAc and molecular weight of PVA. In addition, PVAc microspheres, obtained by these emulsion polymerizations, can be converted to PVA / PVAc shell / core microspheres through a series of surface‐saponifications, maintaining their spherical morphology. Various surface morphologies, such as flat or wrinkled and swellable or nonswellable ones formed by the various molecular parameters and saponification conditions, were examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2356–2362, 2004     

Poly(butylene terephthalate)/organoclay nanocomposites prepared by in situ interlayer polymerization and its fiber (II)

Intercalated nanocomposites with poly(butylene terephthalate) (PBT) incorporated between the montmorillonite layers were synthesized from dimethyl terephthalate and 1,4-butane diol by using an in situ interlayer polymerization. The PBT nanocomposites were melt-spun at different organoclay contents to produce monofilaments. The samples were characterized by using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. The extent of the clay layer in the PBT was confirmed by using X-ray diffraction and electron microscopy, and the clay layer was found to be highly dispersed on a nanometer scale. The addition of only a small amount of organoclay was enough to improve the thermo-mechanical properties of the PBT hybrid fibers. The hybrids were extruded with various draw ratios (DRs) to examine the tensile mechanical property of the fibers. At DR=1, the ultimate tensile strength of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial modulus monotonically increased with increasing amount of organoclay in the PBT matrix. When the DR was increased from 1 to 6, for example, the strength and the initial modulus values of the hybrids containing 3 wt% organoclay decreased linearly.