蒙脱土负载型引发剂的制备及在苯乙烯乳液聚合中的应用

通过正离子交换将引发剂AIBA负载在蒙脱土上制得负载型引发剂V50-MMT.进而采用原位乳液聚合方法引发苯乙烯聚合制备PS/MMT纳米复合材料.采用XRD、TGA、DSC、TEM和抽提等方法对负载型引发剂和纳米复合材料进行了表征.结果表明,负载过程中引发剂AIBA进入了MMT的片层之间;聚合过程中介于片层间的引发剂因发生分解一方面产生自由基引发St聚合,另一方面MMT发生了剥离分散;由此法制备的PS/MMT纳米复合材料,MMT片层无规、均匀地分散于PS基体中,片层厚度在几个纳米至十几个纳米之间,长度为几十至几百个纳米不等;大量的PS链段以化学键接枝在MMT的片层上,接枝在MMT片层上的PS的分子量及其分布与游离的PS不同.     

Synthesis of exfoliated polystyrene/montmorillonite nanocomposite by emulsion polymerization using a zwitterion as the clay modifier

Montmorillonite (MMT) was modified with zwitterion aminoundecanoic acid (AUA). First AUA was protonized to facilitate molecules to get into the galleries of the montmorillonite to accomplish ion exchange, and the carboxyl groups were then ionized in the alkaline aqueous media to enable exfoliation of the clay. It was demonstrated by rheological measurements and atomic force microscopic studies that exfoliation of the clay driven by the electrostatic repulsion took place in an alkaline medium. Polystyrene/montmorillonite (PS/MMT) nanocomposite was synthesized via emulsion polymerization in the presence of the modified MMT. The exfoliated microstructure of the composites was studied by the X-ray diffraction and transmission electron microscopy. The exfoliated PS/MMT nanocomposite showed a greatly improved modulus, a higher glass transition temperature and a better thermal stability compared to the neat polystyrene and the intercalated PS/MMT composites.     

Thermal properties of polystyrene nanocomposites formed from rigid intercalation agent‐treated montmorillonite

Polystyrene (PS)/clay nanocomposites were prepared with two different new intercalation organophilic clays, the phosphonium salt (APP) and the ammonium 4‐(4‐adamantylphenoxy)‐1‐butanamine (APB) salts, by emulsion polymerization technique. X‐ray diffraction and transmission electron microscopy were performed to characterize the layered structures of APB‐ and APP‐treated polymer–clay nanocomposites, and both resulted in exfoliated structures. Molecular weights of PS obtained from these nanocomposites are slightly lower than the virgin PS formed under similar polymerization conditions. Coefficient of thermal expansion showed approximately a 44–55% decrease for APB‐ and APP‐intercalated clay nanocomposites relative to the pure PS. Both T_g and thermal decomposition temperature of the PS component in the nanocomposite are higher than the virgin PS, implying that the presence of clay is able to enhance thermal stabilities of the PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1781–1787, 2007     

Synthesis and characterization of polymer/clay nanocomposites by intercalated chain transfer agent

In situ synthesis of poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanocomposites by free radical polymerization using intercalated chain transfer agent (I-CTA) in the layers of montmorillonite (MMT) clay is reported. MMT clay was ion-exchanged with diethyl octyl ammonium ethylmercaptan bromide, which acts both as suitable intercalant and as chain transfer agent. These modified clays were then dispersed in methyl methacrylate (MMA) or styrene (St) monomers in different loading degrees to carry out the in situ free radical polymerization. The intercalation ability of the chain transfer agent and exfoliated nanocomposite structure were evidenced by both X-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied.     

Preparation and characterization of surfactant-free polystyrene/layered double hydroxide exfoliated nanocomposite via soap-free emulsion polymerization

The soap-free emulsion polymerization has been applied for preparing the surfactant-free polystyrene/layered double hydroxide exfoliated nanocomposite. The XRD and TEM determinations have been used to monitor the changes of interlayer spacing and morphology during polymerization. The results show that the obtained nanocomposite has the homogeneous structure of polymeric and inorganic components. Due to the absence of organic surfactant, the PS/LDH nanocomposite shows a remarked improvement on the onset decomposition temperature compared with virgin PS.     

Influence of polymer matrix composition and architecture on polymer nanocomposite formation: Coarse-grained molecular dynamics simulation

Coarse-grained molecular dynamics simulations of stacks of two-dimensional platelets immersed in a polymer melt were performed to investigate aspects of the polymer matrix that promote the formation of intercalated or exfoliated nanocomposite structures. Such factors include temperature, copolymer architecture, and blend composition. Increasing the polymer-sheet attractive interaction led to binding of the sheets, where individual beads simultaneously attract two neighboring sheets, thus kinetically blocking intercalation by occupying the perimeter of the affected gallery. Polymers with a small polymer-sheet attraction, but having a strongly attractive chain end (end-functionalized polymers) minimized the bonding of adjacent sheets. These systems exhibited some sheet sliding because a majority of the confined polymer beads only interacted weakly with adjacent sheets; however, the number density of intercalated polymer was low. Mixtures of end-functionalized and nonfunctionalized polymers, however, yielded better intercalation efficiency. For the mixed system, the reduced number of highly attractive beads provided sufficient interaction for intercalation to occur, enabling greater intercalation rates, less sheet-bridging, and incorporation of the nonfunctionalized polymers into the galleries. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3272–3284, 2003     

sPS/PA6/蒙脱土纳米复合材料的制备与性能

讨论了间规聚苯乙烯 (sPS) 尼龙 6(PA6) 磺化间规聚苯乙烯 (SsPS H) 蒙脱土纳米复合材料的制备技术和新材料的结构与性能特征 .蒙脱土经层间改性处理后 (MTN) ,可分别将SsPS H和aPS(无规聚苯乙烯 )插入其纳米层间 ,制备出插层型纳米复合物MTN SsPS和MTN aPS .在sPS/PA6/SsPS H三组分共混体系中加入MTN SsPS或MTN aPS ,进行四组分熔融共混即可制备出sPS/PA6/SsPS H/蒙脱土纳米复合材料 .TEM测定证实了蒙脱土在基体中的层厚分布约为 5 0nm .此外 ,采用DSC、DMA、XRD及力学性能测试仪等现代分析方法对sPS/PA6/SsPS H/蒙脱土纳米复合材料的结构与性能进行了详细研究 .研究结果表明这种纳米复合材料具有优良的综合性能     

Pendant cyclic carbonate‐polymer/Na‐smectite nanocomposites via in situ intercalative polymerization and solution intercalation

Nanocomposites of sodium smectite with polyether‐ and polystyrene‐containing pendant cyclic carbonates offer a novel approach to improving hydraulic barrier properties of Na‐smectite liners to saline leachates. The cyclic carbonate polyethers were prepared by cationic ring opening polymerization of a cyclic carbonate‐containing epoxide, whilst polystyrene polymers having pendant cyclic carbonate groups were obtained from radical photopolymerization of styrene. Na‐smectite nanocomposites of these polymers were formed via clay in situ polymerization and solution intercalation methods. X‐ray diffraction (XRD) and FT‐IR analysis confirmed that the polyether can be intercalated within the layers of smectite via in situ as well as solution intercalation of the pre‐formed polymer. The cyclic carbonate polyether nanocomposite was more resistant to leaching in 3M aqueous sodium chloride than its respective cyclic carbonate. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2421–2429     

Gas barrier of polystyrene montmorillonite clay nanocomposites: Effect of mineral layer aggregation

Three polystyrene (PS)/clay hybrid systems have been prepared via in situ polymerization of styrene in the presence of unmodified sodium montmorillonite (Na‐MMT) clay, MMT modified with zwitterionic cationic surfactant octadecyldimethyl betaine (C18DMB) and MMT modified with polymerizable cationic surfactant vinylbenzyldimethyldodecylammonium chloride (VDAC). X‐ray diffraction and TEM were used to probe mineral layer organization and to expose the morphology of these systems. The PS/Na‐MMT composite was found to exhibit a conventional composite structure consisting of unintercalated micro and nanoclay particles homogeneously dispersed in the PS matrix. The PS/C18DMB‐MMT system exhibited an intercalated layered silicate nanocomposite structure consisting of intercalated tactoids dispersed in the PS matrix. Finally, the PS/VDAC‐MMT system exhibited features of both intercalated and exfoliated nanocomposites. Systematic statistical analysis of aggregate orientation, characteristic width, length, aspect ratio, and number of layers using multiple TEM micrographs enabled the development of representative morphological models for each of the nanocomposite structures. Oxygen barrier properties of all three PS/clay hybrid systems were measured as a function of mineral composition and analyzed in terms of traditional Nielsen and Cussler approaches. A modification of the Nielsen model has been proposed, which considers the effect of layer aggregation (layer stacking) on gas barrier. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1733–1753, 2007     

熔体黏度对黏土在聚丙烯/聚苯乙烯共混物中优先插层行为的影响

通过熔融共混法在160℃加工条件下制备了聚丙烯/聚苯乙烯/黏土(PP/PS/clay)复合材料.X射线衍射分析(XRD)和透射电镜分析(TEM)的结果表明,黏土在共混物中存在着优先插层现象.黏土优先被PS分子链所插层,且不受PS组分含量和加料方式的影响.基于复合材料中PP和PS组分的熔体黏度对温度敏感性的差别,通过改变加工温度的方法,研究组分的黏度差别对黏土优先插层行为的影响.随共混加工温度的升高,黏土在共混物中的分布位置逐渐从PS相向PP相迁移.TEM和动态黏弹行为测试(ARES)的结果表明,组分间黏度的差别能控制黏土的优先插层行为.组分黏度越高,加工过程中所能传递的剪切应力就越大,插层能力也就越强.     

Synthesis of poly(methyl methacrylate) nanocomposites via emulsion polymerization using a zwitterionic surfactant

The synthesis of nanocomposites via emulsion polymerization was investigated using methyl methacrylate (MMA) monomer, 10 wt % montmorillonite (MMT) clay, and a zwitterionic surfactant octadecyl dimethyl betaine (C18DMB). The particle size of the diluted polymer emulsion was about 550 nm, as determined by light scattering, while the sample without clay had a diameter of about 350 nm. The increase in the droplet size suggests that clay was present in the emulsion droplets. X-ray diffraction indicated no peak in the nanocomposites. Transmission electron microscopy showed that emulsion polymerization of MMA in the presence of C18DMB and MMT formed partially exfoliated nanocomposites. Differential scanning calorimetry showed an increase of 18 degrees C in the glass transition temperature (Tg) of the nanocomposites. A dynamic mechanical thermal analyzer also verified a similar Tg increase, 16 degrees C, for the partially exfoliated nanocomposites over poly(methyl methacrylate) (PMMA). Thermogravimetric analysis indicated a 37 degrees C increase in the decomposition temperature for a 20 wt % loss. A PMMA nanocomposite with 10 wt % C18DMB-MMT was also synthesized via in situ polymerization. This nanocomposite was intercalated and had a Tg 10 degrees lower than the emulsion nanocomposite. The storage modulus of the partially exfoliated emulsion nanocomposite was superior to the intercalated structure at higher temperatures and to the pure polymer. The rubbery plateau modulus was over 30 times higher for the emulsion product versus pure PMMA. The emulsion technique produced nanocomposites of the highest molecular weight with a bimodal distribution. This reinstates that exfoliated structures have enhanced thermal and mechanical properties over intercalated hybrids.     

聚苯乙烯/蒙脱土熔融插层复合的研究

用熔融法制备了聚苯乙烯／蒙脱土插层复合材料，用Ｘ 射线衍射、ＤＳＣ等手段研究了复合材料的结构与性能．聚苯乙烯熔体不能插层于钠基蒙脱土中，但能插层于经有机化合物处理过的蒙脱土中．     

Effect of an anionic monomer on the pickering emulsion polymerization stabilized by titania hydrosol

Polystyrene (PS) nanocomposite particles with high titania content are prepared by Pickering emulsion polymerization. A self‐made titania hydrosol modified by an anionic monomer sodium styrene sulfonate (NaSS) is used as a stabilizer and photocatalyst. The stability of the emulsion system is greatly improved by the electrostatic interaction between negatively charged NaSS and positively charged titania nanoparticles. The nanocomposite spheres with the diameter of around 120 nm are highly charged, indicating titania‐rich surfaces of latex particles. It is also proven by the field‐emission transmission electron microscope and field‐emission scanning electron microscope images. The well‐defined core‐shell structure of the obtained PS/titania composite particles is confirmed by the formation of fragile hollow titania nanospheres after thermogravimetric analysis tests. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5728–5736, 2009     

聚苯乙烯/层状双金属氢氧化物纳米复合材料的制备与表征

由离子交换法制备4,4′-偶氮二(4-氰基戊酸)根(ACP)单独插层和ACP/对苯乙烯磺酸根(VBS)复合插层的层状双金属氢氧化物(LDH),再通过原位悬浮聚合制得聚苯乙烯(PS)/LDH纳米复合材料,对插层改性LDH和复合材料进行了结构和性能表征.X-射线衍射和元素分析表明ACP可以单独或与VBS一起插入到LDH层间.透射电镜和X-射线衍射分析表明采用ACP/VBS复合插层LDH与苯乙烯原位聚合得到的复合材料中LDH剥离程度高,熔融加工后LDH基本以纳米层板形式分散在PS基体中.LDH的引入可明显提高PS的热稳定性,而熔体流动性下降.     

An investigation of the effect of sodium dodecyl sulfate on quasi-emulsifier-free emulsion polymerization for highly monodisperse polystyrene nanospheres

A quasi-emulsifier-free emulsion polymerization for the synthesis of highly monodisperse polystyrene (PS) microspheres with the diameter less than 100 nm has been developed, which is similar to the conventional emulsifier-free emulsion polymerization except for the addition of a small amount of sodium dodecyl sulfate (SDS) below its critical micelle concentration. To study the effect of SDS on the polymerization, we first explored the nucleation mechanism, and supposed that mixed micelles of SDS and surface active styrene oligomers may be formed and provide indispensable loci for the growth of PS primary particles. As the precursor particles grow, they become unstable and tend to adsorb the rest of SDS not participating in the formation of mixed micelles on their surfaces. Thereby, it reduces the coagulation tendency of the particles, and results in a significant increase of the particle number density which was found to be directly proportional to the square of the surfactant concentration, along with the increase of the polymerization rate and the decrease of the size of final PS particles. In addition, the presence of the surfactant will shorten the duration of the nucleation and, thus, lead to the highly uniform size of PS nanospheres.     

苯乙烯在阴离子型聚氨酯纳米水分散液中聚合过程的研究

采用自乳化法制备出阴离子聚氨酯纳米水分散液,以其作为乳化剂使苯乙烯单体在其中进行聚合,制备出不同聚苯乙烯与聚氨酯质量比的阴离子型PS/PU纳米复合物水分散液;对苯乙烯单体的聚合过程进行了研究;采用光子相关谱仪和透射电镜对其微观结构、粒径及其分布进行了测试,结果表明,该方法能够制备出稳定的具有核壳结构的PS/PU纳米复合物水分散液,但当苯乙烯单体浓度增大到一定程度(PS/PU质量比为50∶100)时,粒子不稳定而发生聚集.     

Exfoliation of layered double hydroxide in polystyrene by in-situ atom transfer radical polymerization using initiator-modified precursor

Exfoliated nanocomposite, based on Zn, Al layered double hydroxide (LDH) and polystyrene (PS), has been achieved by in-situ atom transfer radical polymerization reaction from initiator-modified LDH. The exfoliated structure is characterized by X-ray diffraction and transmission electronic microscope. The results suggest that the exfoliated ZnAl(DS) LDH sheets with a thickness of less than 1 nm disperse individually in the PS matrix, and the thermal stability of the nanocomposite shows a marked improvement. When the 50 wt% weight loss is selected as a comparison point, the decomposition temperature of PS/LDH nanocomposite is about 45 °C higher than that of pure PS.     

亚微米级聚苯乙烯/聚硅氧烷核壳粒子的制备及其应用

以乳液聚合制备的聚苯乙烯乳液为种子,加入甲基三甲氧基硅烷(MTMS)水解溶液进行缩聚反应,合成亚微米级聚苯乙烯/聚硅氧烷核壳粒子,并以此作为光散射剂添加至聚甲基丙烯酸甲酯(PMMA)树脂中,制备了光散射材料;考察了亚微米级核壳粒子添加在PMMA树脂中的分散性。结果表明:经过双螺杆剪切作用的挤出加工后,可以实现核壳粒子在PMMA树脂中的良好分散。核壳粒子可以大幅度提高PMMA的雾度,当聚苯乙烯/聚硅氧烷核壳粒子(NS82)的含量为1%时,制得的PMMA样片(厚度为2 mm)的雾度为89%,透光率为69%,有效光散射系数为61%。     

Preparation of nanocomposites by reversible addition‐fragmentation chain transfer polymerization from the surface of quantum dots in miniemulsion

Herein, we report the synthesis of quantum dots (QDs)/polymer nanocomposites by reversible addition‐fragmentation chain transfer (RAFT) polymerization in miniemulsions using a grafting from approach. First, the surfaces of CdS and CdSe QDs were functionalized using a chain transfer agent, a trisalkylphosphine oxide incorporating 4‐cyano‐4‐(thiobenzoylsulfanyl)pentanoic acid moieties. Using a free radical initiator (AIBN) to activate the RAFT process, a polystyrene (PS) block was grafted from the surface of the QDs. Quantum confinement effects were identified for the nanocomposite obtained, so attesting to the integrity of the QDs after the polymerization. Free PS chains were also present in the final nanocomposite, indicating that the RAFT polymerization from the surface of the QDs was accompanied by conventional free radical polymerization. After isolating the nanocomposite particles, a second poly(n‐butyl acrylate) block was tentatively grown from the initial PS block. The first results indicated a successful polymerization of the second polymer and show the potential of the current strategy to prepare block copolymers from the surface of the RAFT‐modified QDs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5367–5377, 2009     

静电自组装聚电解质/有机染料插层蒙脱土光致变色纳米复合膜

从构筑静电自组装聚电解质／有机染料插层蒙脱土光致变色纳米复合膜所必需 的基本纳米构件--有机染料插层蒙脱土光致变色纳米复合物的设计出发，制备了具有光致 变色功能的蒙脱土／阳离子偶氮染料（GTL）均插层纳米复合物现，插人蒙脱土层 间的GTL热稳定性大幅度提高．由于GTL在纳米受限空间的超分子有序结构共轭，使 偶氮基发生了高达91 nm的显著红移．使用该插层纳米复合物构件与阳离子聚电解 质（PDAC）通过静电自组装得到了生长均匀、排列规整有序的光致变色聚电解质／ 阳离子偶氮染料插层蒙脱土纳米复合膜.