Preparation of transparent polystyrene nano-latexes by an UV-induced routine emulsion polymerization

Transparent polystyrene (PS) latexes were prepared by photo-polymerization of a routine styrene (St) emulsion with a surfactant concentration of 0.4 wt% and a monomer concentration of 10 wt%, by using UV light as well as a hydrophilic photo-initiator. The entire polymerization could be performed within 1-2 h and display a conversion higher than 90%. The particle sizes could be tuned in the range of 20-40 nm. The formation mechanism for these of nano-sized latex particles was attributed to an in situ formation of PS chains with terminal hydroxyl groups. The presence of the hydroxyl-functionalized polymer chains seemed to promote a colloidal stability of the small latex particles and prevent coagulation even at low surfactant concentrations.     

SEM study of a polystyrene/clay nanocomposite

We carried out a scanning electron microscopy study to investigate the morphology of a polystyrene (PS)/montmorillonite nanocomposite. Monodispersed spherical particles, about 200 nm in diameter, were observed when PS/montmorillonite powder was dispersed in water, whereas planar silicate sheets were found for cetyltrimethylammonium bromide‐exchange montmorillonite. The fracture surface of a PS/clay nanocomposite pellet sample showed a lot of fibrils rather than the smooth surface of a pure PS pellet. After the PS/clay nanocomposite pellet was chemically etched, flaky montmorillonite particles were homogeneously dispersed in the PS matrix. A film sample, prepared by the pressing of the PS/clay nanocomposite melt, revealed that the montmorillonite primary particles oriented parallel to the surface, and the corresponding X‐ray diffraction distribution map of silicon atoms confirmed that the dispersed particles were montmorillonite primary particles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 66–69, 2002     

细乳液聚合制备改性硅溶胶／聚丙烯酸酯复合乳液

常温下一步法制备改性硅溶胶,并通过细乳液聚合制备改性硅溶胶／聚丙烯酸酯复合乳液。考查了温度对聚合速率和单体转化率的影响以及不同乳化剂含量下聚合过程中乳胶粒粒径的变化情况;测试了乳胶膜的吸水率,并用接触角法表征了乳胶膜的表面自由能。     

Synthesis and characterization of clay dispersed polystyrene nanocomposite via atom transfer radical polymerization

Finely well‐defined polystyrene nanocomposites were prepared by ATRP method in bulk at 110°C using organically modified montemorillonite, cloisite 30B. The living nature of ATRP reaction was employed to in situ synthesize tailor‐made polystyrene nanocomposite with narrow molecular weight distribution and controlled molecular weight polystyrene chains. The amount of clay loading and time of swelling of clay in the monomer before polymerization were proved to have a positive effect on polymerization rate and also broadened the molecular weight destribution. The gas chromatography (GC) results showed the linear increase of Ln(M₀/M) versus time, which indicates the controlled/living polymerization in the presence of nanoclay. Another confirmation of the living nature of the polymerization was linear elevation of molecular weight against monomer conversion concluded from gel permeation chromatography (GPC) data. X‐ray diffraction analysis showed the interlayer spacing of nanoclay platelets as well as the exfoliated clay morphology in the nanocomposite samples. Transfer electron microscopy (TEM) revealed the exfoliated morphology of the in situ prepared nanocomposite as opposed to conventional solution‐blending technique which resulted in an intercalated structure. The effect of nanoclay on acceleration of polymerization was proved by GC and GPC; similarly, Fourier transform infrared spectroscopy (FTIR) was used to discuss the reasons of such a rate acceleration. A shifting in the wave number of characteristic bonds of nanoclay after polymerization mostly in the case of O H and Si O bonds, revealed the interaction between polymer chains and clay layers which resulted in an accelerated polymerization process. The living nature of polymeric chains was more elucidated by FTIR data. Atomic force microscopy (AFM) images also confirmed the proper dispersion of nanoparticles in the polymer medium. POLYM. COMPOS., 31:1829–1837, 2010. © 2010 Society of Plastics Engineers     

Preparation of high molecular weight monodisperse polystyrene latexes by concentrated emulsion polymerization

The preparation of high molecular weight monodisperse polystyrene (PS) latexes by the concentrated emulsion polymerization is investigated. The PS latexes thus obtained have diameters in the range of 0.1–0.3 μm. The average size and the dispersity of the latexes are dependent on the concentration of surfactant (SDS), the monomer volume fraction, and the amount of monpolymerizable additive (decane). The ionic strength does not seem to affect the size but affect the dispersity of the latexes. Under proper conditions, monodisperse particles can be prepared with a quite small standard deviation. © 1993 John Wiley & Sons, Inc.     

Preparation of polystyrene colloid particles armored by clay platelets via dispersion polymerization

Polystyrene colloid particles armored by Montmorillonite clay (MMT) were prepared by free-radical polymerization in dispersion. MMT was pre-modified with cationic amphiphilic block copolymer of poly(styrene-b-2-hydroxyethyl acrylate) (PS-b-PHEA), and the obtained (PS-b-PHEA)-MMT modified clay was used as stabilizer in dispersion polymerization. The impact of (PS-b-PHEA)-MMT loading on the particle size, the monomer conversion, and on the molecular weight were investigated. The main objective of this paper was to use the clay platelets as stabilizers in dispersion polymerization, and as nanofiller to improve some polymer properties such as thermal stability, thermo-mechanical and melt flow properties. Transmission electron microscopy (TEM) showed that colloid PS particles with MMT layers at the surface (i.e. armored particles) were obtained, and the particles sizes were found to be in the micrometer size range and stable dispersion were obtained for clay loadings up to 5wt%. Small angle X-ray diffractions (XRD) and TEM revealed that polymer-clay nanocomposites (PCNs) with partially exfoliated structures were obtained for low clay loading, while intercalated structures were obtained at higher clay loading. All PCNs were found to be more thermally stable than neat polymer as were determined by TGA. Furthermore, an increase in the storage modulus and the T_g of the PCNs was found and greatly correlated to the clay loading.     

In situ preparation of Mg(OH)2/polystyrene nanocomposite via soapless emulsion polymerization

Magnesium hydroxide nanoneedles modified by oleic acid [OA–Mg(OH)₂] were synthesized via alkaline injection into magnesium chloride solution in the presence of oleic acid (OA). The magnesium hydroxide/polystyrene nanocomposite [Mg(OH)₂/PS] was then prepared by soapless emulsion polymerization technique in an aqueous suspension. The Fourier transform infrared (FT–IR) analysis shows that the polystyrene was covalently grafted onto the surfaces of the Mg(OH)₂nanoneedles [OA–Mg(OH)₂]. The dispersion of Mg(OH)₂nanoneedles in polystyrene is uniform as observed by transmission electron microscope (TEM). The grafting percentage was determined by means of elemental analysis (EA). The thermal behavior determined by the differential scanning calorimetry (DSC) indicated that Mg(OH)₂/PS had a higher glass transition temperature than PS matrix, and it can be concluded that Mg(OH)₂ could retard the degradation of PS based on the data of thermal gravimetric analysis (TGA) and differential thermoanalysis (DTA).     

无皂乳液聚合制备亚微米级单分散聚苯乙烯微球

采用无皂乳液聚合法制备了具有单分散性的亚微米级聚苯乙烯微球,考察了聚合体系pH值、单体及引发剂用量对聚合转化率、微球粒径及其分布的影响。结果表明,采用NaOH和NaHCO,复合溶液调节聚合体系pH值是控制聚合动力学、微球粒径及单分散性的有效手段,当其质量比为1：1时效果较好。随碱性复合溶液加入量的增加,最终转化率下降,微球粒径则由于复合溶液同时起到电解质的作用而存在极大值。随过硫酸钾(KPS)质量分数的增加,反应前期聚合转化率增大,但其用量过大,会导致体系pH值偏低,KPS过早消耗完毕,故反应后期最终转化率偏低;其用量过低,会影响粒径的单分散性。当KPS质量分数为单体的2％～3％时,聚合体系稳定性增加并改善了微球的单分散性,粒径趋小。单体用量的变化对聚合速率影响不大,随单体质量分数的提高,微球最终粒径增大,当单体质量分数过高,会影响微球的单分散性乃至体系失稳,一般以不超过10％为宜。     

种子乳液聚合法制备纳米SiO_2/苯丙复合乳液

采用种子乳液聚合工艺,用经硅烷偶联剂改性后的纳米SiO2原位合成了纳米SiO2/苯丙复合乳液。通过正交实验确定了最佳原料配比和聚合工艺条件,并对复合乳液性能进行了分析与表征。结果表明,当功能单体的用量为单体总量的5%、阴离子乳化剂十二烷基硫酸钠(SDS)与非离子乳化剂辛基苯基聚氧乙烯醚(OP-10)质量比为1颐1、复合乳化剂总量3%、纳米SiO2含量为单体总量的1.5%、聚合温度为80℃时,可制备具有良好综合性能的复合乳液,其涂膜耐水性、硬度、附着力等均优于普通苯丙乳液。该复合乳液乳胶粒粒度呈单峰分布,平均粒径为101nm,具有核/壳结构。     

Synthesis and characterization of PS-clay nanocomposite by emulsion polymerization

Summary Polystyrene-Na⁺-montmorillonite(PS-Na⁺-MMT) nanocomposites are prepared by a simple emulsion polymerization. The X-ray diffraction(XRD) and infrared spectroscopy (IR) analysis confirm that polystyrene(PS) macromolecules can be inserted between lamella layers and whose layer separation is consequently higher than in the polymer-free clay. The enhanced thermal properties of composites are measured by differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA) thermogram and indicate that the glass transition and the decomposition onset temperature of obtained nanocomposites are found to be moved to the higher temperature region. The increased Young's modulus of the obtained nanocomposites is ascribed to the intercalation of PS in clay galleries as well as the fine dispersion of clay particles into the polymer matrix. Received: 23 February 1999/Revised version: 26 March 1999/Accepted: 1 April 1999     

原位悬浮聚合制备酸性酚醛树脂 /蒙脱土纳米复合材料

在酸性催化剂作用下,采用悬浮聚合的方法制备了酸性酚醛树脂/蒙脱土纳米复合材料。XRD和TEM的实验结果表明该材料结构为部分剥离、部分插层型,即一部分蒙脱土被剥离为单层,而另一部分为几个片层的聚集体。     

无机-有机纳米复合乳液的原位聚合及其应用

综述了原位乳液聚合法制备无机．有机纳米复合乳液的技术现状及其形成机理，并运用此技术合成了舍无机纳米粒子的压敏胶用无机-有机纳米复合乳液，分析了纳米粒子在制备过程中的分散性能，从纳米粒子引入方式、乳化剂用量、纳米粒子加入量3方面对压敏胶性能进行考查。     

无皂乳液聚合制备多孔聚苯乙烯纳米微球

苯乙烯(St)单体、过硫酸钾(KPS)和二乙烯基苯(DVB)通过无皂乳液聚合,在70℃下反应8 h,合成聚苯乙烯(PS)纳米粒子,PS磺化,得到磺化聚苯乙烯(SPS),通过正庚烷和乙醇溶胀后,水进入粒子内部发生相分离,形成多孔聚苯乙烯PS,在-30 k Pa负压条件下,负载缓蚀剂苯丙三氮唑(BTA)。考察单体量和反应时间对粒子形态的影响。结果表明,采用10 g St,0.05 g KPS,100 mL去离子水,反应2 h后加入0.05 g DVB,可以得到粒径合适、球形完整的PS纳米微球。PS微球磺化6 h,n(乙醇)∶n(水)∶n(正庚烷)=5∶5∶1,造孔10 h时,可得到形貌和孔径合适的多孔SPS纳米微球。SEM、TEM和FTIR表明,多孔SPS微球表面和内部负载上了一定量的缓蚀剂BTA。     

Synthesis and characterization of polystyrene/layered double‐hydroxide nanocomposites via in situ emulsion and suspension polymerization

Polystyrene (PS)/ZnAl layered double‐hydroxide (LDH) nanocomposites were synthesized via in situ emulsion and suspension polymerization in the presence of N‐lauroyl‐glutamate surfactant and long‐chain spacer and characterized with elemental analysis, Fourier transform infrared spectrum, X‐ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis. The XRD and TEM results demonstrate that the exfoliated ZnAl–LDH layers were well dispersed at molecular level in the PS matrix. The completely exfoliated PS/LDH nanocomposites were obtained even at the 20 and 10 wt % LDH loadings prepared by emulsion polymerization and suspension polymerization, respectively. The PS/LDH nanocomposites with a suitable amount of LDH showed apparently enhanced thermal stability. When the 50% weight loss was selected as a comparison point, the decomposition temperature of the exfoliated PS/LDH sample prepared by emulsion polymerization with a 5 wt % LDH loading was about 28°C higher than that of pure PS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3758–3766, 2006     

蒙脱土/碳纳米管多维增强的聚乙烯复合材料的制备

引言聚烯烃是国民生活和现代国防不可或缺的基础原材料,但与ABS、PC等工程塑料相比,其刚性不足,低温脆性也较明显,因此很难作为结构材料使用。纳米技术的出现为聚烯烃材料性能的提高提供了广阔的空间[1],其中,纳米复合材料中存在纳米尺寸效应、超大的比表面积以及很强的界面相互作用,具有比强度高、可设计性强、抗疲劳性好等优点,因此,纳米复合聚乙烯中含少量纳米材料便能极大增强材料本身的性能,同时聚合物中纳米材料的低含量也大大减少了无机载体在聚合物中的灰分,有利于聚合物材料高性能的保持,这引起了研究工作者的广泛关注。     

Preparation of polymeric microcapsules enclosing microbial cells by radical suspension polymerization via water-in-oil-in-water emulsion

Polymeric microcapsules enclosing Saccharomyces cerevisiae were prepared by radical suspension polymerization via water-in-oil-in-water emulsion. Trimethylolpropane trimethacrylate and 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) were used as monomer and radical initiator, respectively. A culture medium with suspended yeast cells, monomer solution with the dissolved radical initiator, and poly(vinyl alcohol) aqueous solution were used as inner aqueous phase, oil phase, and outer aqueous phase, respectively. The influence of microcapsule preparation parameters on the viability of encapsulated cells and encapsulation efficiency was investigated. The radical polymerization process did not cause significant damage to encapsulated yeast cells. Decreased weight ratio of aqueous phase to oil phase resulted in increased encapsulation efficiency of the cells. The diameter of the microcapsules could be controlled by varying the agitation rate.     

Aqueous core polystyrene microspheres fabricated via suspension polymerization basing on a multiple pickering emulsion

Multi‐hollow or hollow polymer particles are of great interest in many fields. Here we successfully fabricate polystyrene microspheres with aqueous cores through w/o/w Pickering emulsion stabilized by modified SiO₂ nanoparticles. The final structure and constituents of the microspheres is investigated via SEM, X‐ray photoelectron spectra, and thermo‐gravimetric analysis. The results demonstrate that the size and amount of aqueous cores in the microspheres can be tuned by the original structure of the multiple emulsions: when the volume fraction of inner water is 0.2, the inner structure of the microspheres obtained is porous and each pore is not interconnected; when the volume fraction of inner water is increased to 0.7, the resulting products are hollow microspheres and when 0.3% wt/vol of salt is added to the inner aqueous phase, the inner pores of the resulting microspheres enlarge or even coalesce. The multi‐hollow or hollow polystyrene microspheres with aqueous cores are expected to be candidates for encapsulation in biotechnology. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39761.     

Preparation and characterization of polystyrene/modified carbon black composite beads via in situ suspension polymerization

A facile and effective method was introduced into this article to modify carbon black (CB). Fourier‐transform infrared spectrum demonstrates the chemical structure of CB has obviously changed after surface modification. Compared with pure CB, the thermogravimetric analysis illustrates thermal behavior of modified CB (MCB) exhibits a well‐defined difference from CB. Besides, aggregation phenomenon existed in CB is weakened evidently after surface modification. A series of polystyrene (PS) composite beads in presence of MCB were synthesized via in situ suspension polymerization process. The effects of benzoyl peroxide dosage and MCB dosage on the polymerization time of PS composite beads were systematically researched. After modification, the inhibition effect of MCB on the polymerization of PS/MCB composite beads is obviously weakened. The dispersion of MCB in PS/MCB composite beads is greatly improved than that of CB in PS/CB composite beads. Moreover, PS/MCB beads have the better thermal stability than that of PS and PS/CB composite beads. POLYM. COMPOS., 34:1110–1118, 2013. © 2013 Society of Plastics Engineers     

Preparation of polymer/graphite conducting nanocomposite by intercalation polymerization

An in situ polymerization was conducted in the presence of expanded graphite obtained by rapid heating of the graphite intercalation compound (GIC) to form a polymer/expanded graphite conducting composite. Study showed that the graphite was dispersed in the form of nanosheets in the polymer matrix. The transition from an electrical insulator to an electrical semiconductor for the composite occurred when the expanded graphite content was 1.8 wt %, which was much lower than that of conventional conducting polymer composite. The composite exhibited high electrical conductivity of 10⁻² S/cm when the graphite content was 3.0 wt %. This great improvement of conductivity could be attributed to the high aspect ratio (width-to-thickness) of the graphite nanosheets. Study suggested that extensive rolling of the blend greatly affected the conductivity of the composite. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2506–2513, 2001     

Preparation of emulsifier‐free polystyrene by conventional emulsion polymerization with a hydrolysable emulsifier

An alkali‐hydrolyzable surfactant, (1‐tetradecyloxycarbonyl)trimethylammonium chloride, was used as an emulsifier for emulsion polymerization of styrene inwater. The polymerization yielded a high molecular‐weight polymer almost quantitatively. Addition of a small amount of NaOH to the resulting latex solution precipitated the polymer immediately. Analysis of the centrifuged solid indicated almost perfection of both recovery of the polymer and removal of surface‐active species from it. Minimization of ionic species in the polymer solid was confirmed by a high contact angle of the polymer film with water. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008