New Nanocomposites Based on Syndiotactic Polystyrene and Organo-Modified ZnAl Layered Double Hydroxide

New nanocomposites were prepared by mixing syndiotactic polystyrene (sPS) with organo-modified ZnAl layered double hydroxide (O-ZnAl-LDH) in toluene solution. Both wide-angle X-ray diffraction (WXRD) and transmission electron microscopy (TEM) examinations confirmed the nanocomposite formation with exfoliated or intercalated O-ZnAl-LDH distributed in the sPS matrix. Meanwhile, the nonisothermal crystallization behavior of the resulting nanocomposites was studied using differential scanning calorimetry (DSC) technique at various cooling rates. The results indicated that the O-ZnAl-LDH particles in nanometer size might act as nucleating agents and accelerate the overall nonisothermal crystallization process.     

In situ Production of Polystyrene Magnetic Nanocomposites through a Batch Suspension Polymerization Process

This work presents the synthesis of micro‐sized polystyrene magnetic beads by in situ incorporation of oleic acid‐modified Fe₃O₄ magnetic nanoparticles via a suspension polymerization process. Fe₃O₄ nanoparticles with superparamagnetic characteristics were obtained through a coprecipitation technique. These particles present an average diameter equal to 7.4 ± 4.6 nm, as determined by AFM. This result is in agreement with the crystallite size of single domains calculated by using Scherrer's equation, which was equal to 7.7 nm, based on XRD measurements. The obtained materials were also studied using TGA. The weight loss behavior was independent of the Fe₃O₄ content and the stability to the thermal degradation was also not improved by magnetic nanoparticles present in the composite. Polystyrene/Fe₃O₄ magnetic nanocomposites exhibited the same diffraction peaks observed in the pure Fe₃O₄, which indicates that nanoparticles inside the composites preserved the structure and properties of pure Fe₃O₄. It was also shown that nanosized polystyrene particles, dispersed in the aqueous phase, are obtained due to the stabilization effect of the oleic acid on the styrene droplets. A cross‐section of polystyrene magnetic particles showed empty spherical regions, attributed to the encapsulation of water microdroplets during the polymerization reaction. The obtained polymeric materials also presented good magnetic behavior, indicating that the modified Fe₃O₄ nanoparticles were successfully dispersed in the polystyrene particles.

     

间规聚苯乙烯的合成与工业化研究

本文评述了间规聚苯乙烯（ｓＰＳ）的联合机理与工业化研究,介绍了茂金属催化剂和聚合反应器。强调要实现ｓＰＳ的工业化,尚需加强以聚合反应工艺和反应器开发为目标的聚合反应工程研究。     

Intercalated PS/Na+‐MMT Nanocomposites Prepared by Ultrasonically Initiated In Situ Emulsion Polymerization

Summary: A new technique, ultrasonically initiated in situ emulsion polymerization, was employed to prepare intercalated polystyrene/Na⁺‐MMT nanocomposites. FTIR, XRD, and TEM results confirm that the hydrophobic PS can easily intercalate into the galleries of hydrophilic montmorillonite via ultrasonically initiated in situ emulsion polymerization, taking advantages of the multi‐effects of ultrasonic irradiation, such as dispersion, pulverization, activation, and initiation. Properly reducing SDS concentration is beneficial to widen the d‐spacing between clay layers. However, the Na⁺‐MMT amount has little effect on the d‐spacing of nanocomposites. The glass transition temperature of nanocomposites increased as the percentage of clay increased, although the average molecular weight of PS decreased, and the decomposition temperature of the 1obtained nanocomposites moves to higher temperature.

TEM of PS/Na⁺‐MMT nanocomposite prepared by ultrasonically initiated in situ emulsion polymerization.     

在位分散聚合制备聚苯乙烯／凹凸棒土复合材料

采用超声分散处理凹凸棒土，分别采用季胺盐表面活性剂（A）和硅烷偶联剂（B）对其进行表面修饰，采用原位聚合的方法制备出聚苯乙烯／凹凸棒土复合材料，利用SEM，TEM，DMA等测试手段比较两种处理方法得到的复合材料的性能。结果表明：通过超声分散的方法可以得到凹凸棒土纳米级微粒子，硅烷偶联剂在凹凸棒土棒晶的表面形成了柔性的界面层，硅烷处理在一定程度上可以达到增强增韧的作用。季胺盐处理可以中和凹凸棒土表面的Lewis酸，避免了低聚物的生成，凹凸棒土的用量对体系的动态力学行为和力学性能有较大的影响。     

Bio‐Based Nanocomposites from Corn Oil and Functionalized Organoclay Prepared by Cationic Polymerization

A reactive organic montmorillonite clay (VMMT), modified with (4‐vinylbenzyl) triethylammonium cations, has been prepared and used as a nanofiller to reinforce a corn‐oil‐based polymer resin. The polymer resin was prepared by the cationic polymerization of conjugated corn oil, styrene and divinylbenzene, using boron trifluoride diethyl etherate modified with Norway fish oil as the initiator. The results indicate that the VMMT is intercalated in the corn‐oil‐based polymer resins. When compared with the pure polymers, these novel nanocomposites reinforced with 2 to 3 wt.‐% VMMT exhibit significant improvements in modulus, strength, strain and toughness. Furthermore, incorporating VMMT into the corn‐oil‐based polymer matrix also leads to improved thermal stability of the nanocomposites over the pure resins of up to 400 °C.

     

Preparation of Polystyrene/Clay Nanocomposites by Free‐Radical Polymerization in Dispersion

Fully exfoliated PS/clay nanocomposites were prepared via FRP in dispersion. Na‐MMT clay was pre‐modified using MPTMS before being used in a dispersion polymerization process. The objective of this study was to determine the impact of the clay concentrations on the monomer conversion, the polymer molecular weight, and the morphology and thermal stability of the nanocomposites prepared via dispersion polymerization. DLS and SEM revealed that the particle size decreased and became more uniformly distributed with increasing clay loading. XRD and TEM revealed that nanocomposites at low clay loading yielded exfoliated structures, while intercalated structures were obtained at higher clay loading.

     

In Situ Polymerization and Characterization of Aniline and O-Anthranilic Acid Copolymer/Pyrogenic Silica Nanocomposites

Copolymers of aniline and o-anthranilic acid/amorphous fumed silica nanocomposite are synthesized by 5:1 molar ratios of the respective monomers with different percentages of silica nanoparticles via in situ chemical co-polymerization. The electrical conductivity and spectral characteristics upon incorporation of o-anthranilic acid units into the polyaniline backbone in presence of silica nanoparticles are investigated. The results are justified by measuring the UV-Vis absorption spectra, FT-IR for PANAA copolymer, and in situ PANAA/silica nanocomposite. Also, the thermal gravimetric analysis for the copolymer powder formed in the bulk in absence and in presence of silica nanoparticles are carried out.     

Synthesis and Characterization of Polystyrene‐Encapsulated Laponite Composites via Miniemulsion Polymerization

Summary: A novel polystyrene‐encapsulated laponite composite system has been developed via a miniemulsion polymerization approach. The encapsulation mechanism and process parameters have been examined in detail using light‐scattering, sedimentation analysis, wide‐angle X‐ray diffraction (WXRD), and transmission electron microscopy (TEM). The laponite was encapsulated through a miniemulsion polymerization process in which laponite was predispersed in the monomer phase. The stability of both the miniemulsion and the latex depends on initiation loci, premixing procedures, intensity and time of ultrasonification and the surfactants and co‐stabilizer used. Hydrophobicity of the laponite clay played a vital role in both the encapsulation of the clay and the stability of the latex. A quaternary ammonium salt, cetyltrimethylammonium bromide (CTAB), was mixed with the clay in the monomer phase prior to emulsification. As a result, the clay particles were hydrophobically modified and were intercalated. The hydrophobicity not only favored the clay dispersion in the oil droplets but also aided the entry of the monomer into the clay's intergalleries during polymerization. Meanwhile, CTAB helped stabilize the system when it was used in conjunction with the nonionic surfactant polyoxyethylene (40) isooctylphenyl ether (TX‐405). In this way, the laponite is effectively encapsulated within a polystyrene shell in a stable latex form. More importantly, the polymerization initiated in the intergalleries of the clay effectively expands the clay's platelet array to form an exfoliated structure.

     

Novel Polyamide 6/Polystyrene In Situ Microfibrillar Blends Prepared by Anionic Polymerization of ε‐Caprolactam via Reactive Extrusion

In this study, polyamide 6/polystyrene in situ microfibrillar blends are prepared via anionic polymerization of ε‐caprolactam in a twin screw extruder. Scanning electron microscope analysis reveals that microfibrillated PA6 dispersed phase, which is continuous and preferentially oriented parallel to the extrusion direction, is in situ formed within polystyrene (PS) matrix during reactive extrusion at the content PS equal to 30 and 40 wt%. Mechanical properties analysis shows that the yield strength and elongation at break of PA6/PS (70/30 and 60/40) microfibrillar blends are remarkably increased with respect to those of pure PS. Also, the in situ fibrillation mechanisms are investigated by the analysis of morphological evolution. This work demonstrates a facile and efficient route to fabricate the microfibrillar blends with relatively high contents of polymer microfibrils.

     

High-Performance and Biobased Polyamide/Functionalized Graphene Oxide Nanocomposites through In Situ Polymerization for Engineering Applications

In this study, biobased polyamide/functionalized graphene oxide (PA-FGO) nanocomposite is developed using sustainable resources. Renewable PA is synthesized via polycondensation of hexamethylenediamine (HMDA) and biobased tetradecanedioic acid. Furthermore, GO is functionalized with HMDA to improve its compatibility with biobased PA and in situ polymerization is employed to obtain homogeneous PA-FGO nanocomposites. Compatibility improvement provides simultaneous increases in the tensile strength, storage modulus, and conductivity of PA by adding only 2 wt% FGO (PA-FGO2). The tensile strength and storage modulus of PA-FGO2 nanocomposite are enhanced dramatically by ≈50% and 30%, respectively, and the electrical conductivity reached 3.80 × 10^–3 S m⁻¹. In addition, rheology testing confirms a shear-thinning trend for all samples as well as a significant enhancement in the storage modulus upon increasing the FGO content due to a rigid network formation and strong polymer-filler interactions. All these improvements strongly support the excellent compatibility and enhanced interfacial interactions between organic–inorganic phases resulting from GO surface functionalization. It is expected that the biobased PA-FGO nanocomposites with remarkable thermomechanical properties developed here can be used to design high-performance structures for demanded engineering applications.     

Preparation and Properties of High Performance Multilayered PANi/PMMA/PPG-b-PEG-b-PPG/FGHMDA Nanocomposites via in Situ Polymerization

In this attempt, novel conjugated polymer/graphite nanocomposites with exposed surface area were fabricated by in situ polymerization using polyaniline, poly(methyl methacrylate) and poly(propylene glycol)-block-poly(ethylene glycol) block- poly(propylene glycol) as matrices and functionalized graphite as a filler. Structural and morphological analysis revealed the modification of graphite as well as oxidative polymerization of numerous matrices over the surface of modified graphite ensuing multilayered nanocomposites. The increased values of T_g (59 and 103°C) obtained from thermal analysis reflect the improved thermal stability of prepared nanocomposites and exhibit better adsorption capacity (35.5cm³/g). Maximum electrical conductivity (7.4 S/cm) was also observed for multilayered nanocomposite.     

Water-Based PMMA-Nano-CaCO3 Nanocomposites by In Situ Polymerization Technique: Synthesis,Characterization and Mechanical Properties

Water-based nanocomposite was synthesized using in-situ polymerization of Methyl Methacrylate. Nano-CaCO₃ was added during polymerization along with aqueous solution of surfactant. Quantity of nano-CaCO₃ was varied as 0, 2 and 4% of monomer quantity. XRD gram shows the presence of nano-CaCO₃, which causes the crystalline nature to nanocomposites. TEM images of nano-CaCO₃ show cubic structure. Synthesis of nanocomposite follows pseudo–first-order kinetics polymerization. PMMA-4% CaCO₃ nanocomposite showed significant improvement in UV absorbance and in mechanical properties like adhesion, scratch resistance as compared to neat PMMA and 2% CaCO₃ nanocomposite.     

Electrically Conductive Polystyrene/Polypyrrole Nanocomposites Prepared via Emulsion Polymerization

Polypyrrole (PPy) nanoparticles in polystyrene (PS) matrix were synthesized by emulsion polymerization using ferric sulfate, sodium dodecyl sulfate, and n-amyl alcohol as an oxidant, emulsifier and dopant, and co-emulsifier, respectively. The content of PPy nanoparticles in the composites varied from 14.11 to 34.63 wt%, as calculated from elemental analysis. Field Emission Scanning Electron Microscopy images showed spherical nanopartciles of PPy with diameters of 30–74 nm were well dispersed in PS matrix. It was found that the thermal stability and electrical conductivity of PS/PPy composites increased with increasing content of PPy nanoparticles.     

聚丙烯/蒙脱土纳米复合材料的结构及物理性能研究

采用化学反应法制备了Ziegler-Natta/有机改性蒙脱土复合催化剂,并通过丙烯单体原位插层聚合法制备出聚丙烯/蒙脱土(PP/MMT)纳米复合材料,研究了复合材料的微观结构、热性能以及加工稳定性等。结果表明,原位聚合法制备的复合材料为剥离型纳米复合材料,其中MMT片层以纳米尺寸均匀分散在PP基体中,MMT平均厚度小于10nm;随MMT含量的提高,复合材料的热稳定性提高;原位聚合制备的PP/MMT纳米复合材料在长时间剪切过程中部分MMT会发生自聚集,控制剪切时间可以有效防止MMT的自聚集;原位聚合制备的PP/MMT复合材料(粉料)中,PP以α晶型为主,纳米MMT的引入并不会诱导生成聚丙烯β晶型,复合材料中β晶型的出现与退火条件有关。     

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     

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。     

In Situ Synthesis of Mg/Si Polymer Composites via Emulsion Polymerization

Summary: Different styrene‐ and acrylate‐based organic‐inorganic polymer composites incorporating magnesium hydroxide were successfully synthesized using MPTMS as a coupling agent and MgCl₂ as an inorganic precursor. The polymer composites were prepared by free‐radical emulsion polymerization following different procedures. The samples were investigated by means of FT‐IR spectroscopy, XRD, TGA, DSC, and rheometry. It is shown that the preparation method does only affect the ratio of organic to inorganic component, but not the chemical structure of the composites. The obtained polymer composites consist of Mg(OH)₂ particles which are linked covalently via MPTMS groups to the polymer backbone.

Scheme of Mg(OH)₂ crosslinked with MPTMS units as proposed for the emulsion polymer composite.     

原位插层聚合法制备共聚酯/蒙脱土纳米复合材料

采用原位插层聚合法,制备了蒙脱土含量较高的共聚酯/蒙脱土纳米复合材料,意在做母料使用,含有该母料的聚合物复合材料的染色性能、吸湿浸润性能、抗静电性能及抗紫外性能等都有所改善。阐述了合适的共聚酯/蒙脱土纳米复合材料的制备工艺,讨论了制备过程中的影响因素,结果发现:在采用酯交换-缩聚反应釜进行原位插层聚合制备共聚酯/蒙脱土纳米复合材料的过程中,蒙脱土在缩聚釜中加入更符合生产实际;缩聚反应的实际过程证明了蒙脱土中含有的金属离子对缩聚反应有催化作用;另外,控制聚合的最终温度不超过278℃。最后,对共聚酯/蒙脱土纳米复合材料的结构进行了表征。     

Syndiotactic polymerization of styrene: Study of catalyst components and polymerization conditions

Syndiotactic polystyrene (s‐PS) was prepared using monotitanocene catalyst of cyclopentadienyl titanium trichloride (CpTiCl₃) activated by methylaluminoxane (MAO). Solution polymerization was carried out in toluene using different polymerization conditions. Syndiotacticity index (SI) between 68 and 91.6% was obtained. Increasing Al/Ti molar ratio shows an increase in both conversion percentage and SI. The conversion increased linearly with increasing Al/Ti molar ratio in the range studied. The conversion reached to an optimum value of about 65% at styrene/Al molar ratio of 2.83, while no regular behavior of SI was observed with changing the ratio. Effect of temperature of the range 50–80°C on polymerization was studied. The most favorable temperature for the polymerization regarding activity is 70°C; however SI decreased with temperature up to 80°C. H₂ value to 140 mL/100 mL solvent increased the productivity of the catalyst, however further increase of H₂ reduced the activity of the catalyst. Polymerization time of 15 to 125 min shows a decrease in activity. The decrease was sharper for about 30 min of polymerization than longer time. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2216–2221, 2006