Nanocomposites Based on Chitosan-Graft-Poly(N-Vinyl-2-Pyrrolidone): Synthesis,Characterization, and Biological Activity

Organophilic montmorillonite (OMMT) was synthesized by cationic exchange between Na⁺-MMT and N-octyl-N-vinyl-2-pyrrolidonium bromide. Chitosan graft copolymer nanocomposites were synthesized by grafting N-vinyl-2-pyrrolidone onto chitosan in aqueous acetic acid in the presence of OMMT using free radical polymerization. The chemical structures were verified by FTIR. Scanning electron microscopy showed a surface roughness for chitosan graft nanocomposites. Wide-angle X-ray diffraction confirmed the intercalation of grafted chitosan chains between OMMT galleries. Thermogravimetric analysis indicated that the thermal stability of grafted chitosan was enhanced by OMMT incorporation. Preliminary studies showed that the nanocomposites exhibited antimicrobial activity compared with chitosan graft copolymer.     

Sulfonated Styrene-(ethylene-co-butylene)-styrene/Montmorillonite Clay Nanocomposites: Synthesis, Morphology, and Properties

Sulfonated styrene-(ethylene-butylene)-styrene triblock copolymer (SSEBS) was synthesized by reaction of acetyl sulfate with SEBS. SSESB-clay nanocomposites were then prepared from hydrophilic Na-montmorillonite (MT) and organically (quaternary amine) modified hydrophobic nanoclay (OMT) at very low loading. SEBS did not show improvement in properties with MT-based nanocomposites. On sulfonation (3 and 6 weight%) of SEBS, hydrophilic MT clay-based nanocomposites exhibited better mechanical, dynamic mechanical, and thermal properties, and also controlled water–methanol mixture uptake and permeation and AC resistance. Microstructure determined by X-ray diffraction, atomic force microscopy, and transmission electron microscopy due to better dispersion of MT nanoclay particles and interaction of MT with SSEBS matrix was responsible for this effect. The resulting nanocomposites have potential as proton transfer membranes for Fuel Cell applications.     

Synthesis,Characterization of Poly (4-vinyl Pyridine/Vinyl Acetate) Organo Montmorillonite Clay Composites Prepared by Chemical Initiation and their Metallated Products

The nanocomposite of different ratios of (4-vinyl pyridine (VP) vinyl acetate (VAc) copolymers), with montmorillonite (Bent), was prepared by direct interaction of sodium montmorillonite (Bent). It was found that the interaction occurred, through ion exchange between sodium cations in Bent and pyridinium ions, in the copolymers. The structure of the prepared composite was confirmed via X-ray diffraction, thermal stability via thermogravimetric analysis and scanning electron microscope. Also, the formation of metallo composites with Cu⁺², Hg⁺², and Co⁺² cations, and their antimicrobial activities were investigated. The results indicated that the prepared composite exhibited antibacterial activities.     

Preparation,Characterization and Properties of Poly(vinyl chloride)/CaSO4 Nanocomposites

Poly(vinyl chloride)/CaSO₄ nanocomposites were prepared on Brabender plasticorder. Moreover, for comparison PVC/ commercial CaSO₄ composites was prepared. The amount of loadings of nano CaSO₄ and commercial CaSO₄ was in the range of 0–12 wt%. Nano CaSO₄ was synthesized by matrix-mediated growth technique. The size and shape of nano CaSO₄ were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). These PVC nanocomposites were then subjected to mechanical, thermal analysis on UTM, and TGA respectively. Morphology studies of PVC nanocomposites were done on scanning electron microscope (SEM). The morphology study showed that nano CaSO₄ get exfoliated and intercalated with the PVC matrix. Notched Charpy impact strengths of PVC nanocomposites was drastically improved compared to that of pristine PVC and commercial CaSO₄ composites. PVC/CaSO₄ nanocomposites showed higher values of tensile strength, elongation at break and impact strength than PVC/CaSO₄ (commercial) composites. Impact strengths also gives some drastic dependence on nano CaSO₄ content and give a maximum value at certain CaSO₄ loadings.     

Preparation and Characterization of Graft Copolymer EVA-g-PU

Via melting graft reaction, a new type of graft copolymer EVA-g-PU was synthesized. The characterization of Fourier transform infrared and ¹³C -nuclear magnetic resonance indicated that the polyether-polyurethane prepolymer was grafted on the EVA main chain successfully. Differential scanning calorimetry testing showed that the melting temperature increased with the increase of PU prepolymer content. The enhanced storage modulus of EVA-g-PU was characterized by dynamic mechanical thermal analysis. The enhanced degree in the storage modulus of EVA-g-PU increased with the increase of PU prepolymer content. Thermal gravimetric analysis testing showed that thermal stabilities of EVA-g-PU increased with the increase of PU prepolymer content.     

Preparation and Characterization of Biodegradable Polyurethane Nanocomposites Based on Poly(3-hydroxybutyrate) and Poly(Butylene Adipate) Using Reactive Organoclay

Polyurethane nanocomposites were synthesized using one-step solution polymerization of poly(3-hydroxybutyrate)-diol, poly(butylene adipate)-diol using 1,6-hexamethylene diisocyanate. Nanocomposites were prepared using an in-situ polymerization method. The structure was verified using FTIR and ¹HNMR. Morphology was examined by XRD and TEM methods. Thermal properties were examined using DSC and TG. DSC showed that all samples were semicrystalline. The Cloisite 30B enhanced the melt crystallization of PHB segments while hindering those of the PBA segments. Thermal stability was improved compared to the neat PUs samples. The Coats-Redfern model was used to calculate the activation energy. Mechanical properties were improved with incorporation of organoclays.     

酚醛树脂/蒙脱土纳米复合材料的制备和表征

在醋酸锌催化剂作用下,采用边缩聚边插层的一步法制备了酚醛树脂／蒙脱土杂化树脂,并采用对甲苯磺酸为室温固化剂制得酚醛树脂／蒙脱土复合材料。傅立叶红外光谱和X-射线衍射分析表明：苯酚和甲醛可以进入蒙脱土硅酸盐片层间并进行缩聚反应,一方面,在缩聚过程中蒙脱土层间距d00。进一步扩大;另一方面,经缩聚反应得到的含羟甲基的酚醛树脂预聚物可与蒙脱土硅酸盐片层间羟基发生化学反应。热失重分析数据说明,随着蒙脱土含量的增加,酚醛树脂／蒙脱土固化物的耐热性提高。     

尼龙66／蒙脱土纳米复合材料的制备与表征

利用熔体插层法制备了尼龙66／蒙脱土纳米材料复合材料,测试了力学性能、热性能。通过XRD、TEM等手段,研究了蒙脱土在基体中的分散情况。结果表明,蒙脱土以10－100nm的尺寸均匀分散于尼龙66中,所得到的复合物的性能较尼龙66有较大提高。     

Thermal and Morphological Properties of Poly(vinyl alcohol) and Layered Double Hydroxide (LDH) Nanocomposites

Poly(vinyl alcohol) (PVA)/layered double hydroxide (LDH) nanocomposites were synthesized with different compositions: 0, 2, 4, 6, and 8 wt% of LDH by the solution intercalation method. The effects of the layered double hydroxide platelet concentration on the properties of the PVA/LDH films were investigated by thermogravimetric analysis (TGA), optical microscopy, and Fourier transform infrared spectroscopy (FTIR). A reduction in the onset of thermal decomposition temperature was observed in PVA/LDH composites compared to neat PVA. The reduction in the onset of thermal decomposition was likely due to a nucleophilic attack mechanism. The presence of single LDH sheets in form strips in the optical micrographs shows direct evidence of exfoliation, indicating that LDH layers were well-exfoliated and dispersed in the PVA matrix in a disorderly fashion. The FTIR analysis showed good interaction between the continuous PVA matrix and the LDH nanoparticle fillers, by hydrogen bonding through hydroxyl groups. The primary focus of the present investigation was to explore the potential of LDH material as a nanofiller and to improve dispersion of LDH in polar polymers like PVA.     

Mechanical,Morphological and Thermal Properties of Polycarbonate/SEBS-G-MA/Montmorillonite Nanocomposites

Nanocomposites based on polycarbonate (PC) containing sodium montmorillonite (NaMMT) and maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MA) were prepared by melt compounding method followed by injection molding. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed the formation of intercalated nanocomposites. Incorporation of SEBS-g-MA into the PC/MMT nanocomposites enhanced ductility and impact strength but slightly reduced tensile strength and stiffness. The glass transition temperature (T _g – detected from DMTA) and onset temperature (T _onset – detected from TGA) of the PC nanocomposites was increased in the presence of SEBS-g-MA. For this PC/NaMMT system, SEBS-g-MA could act as an effective toughening agent.     

聚丙烯/蒙脱土纳米复合材料的制备与性能

合成了TiCl4/MgCl2/MMT插层催化剂,通过原位聚合制备了聚丙烯/蒙脱土纳米复合材料。X射线衍射结果表明:蒙脱土在聚丙烯基质中达到了纳米级分散。与纯聚丙烯(PP5004)相比,聚丙烯/蒙脱土纳米复合材料的力学性能、维卡软化点、热变形温度以及热分解温度都有所提高。     

Synthesis and Characterization of Polystyrene-b-Poly(4-vinyl pyridine) Block Copolymers by Atom Transfer Radical Polymerization

We aimed at the synthesis of well-define PS-b-P4VP by using atom transfer radical polymerization in two-step process. First, polystyrenes with benzyl bromide end group (PS-Br; by ATRP) were prepared as macroinitiator for the next ATRP of 4-vinyl pyridine and characterized these polymers from ¹H-NMR and MALDI-TOF. Comparing with MALDI-TOF-MS, ¹H-NMR and GPC analyses, this indicates that the formation of the block copolymer can be observed. During the polymerizations, molecular weight distribution and kinetics have been evaluated from GPC traces and ¹H-NMR analyses. We further characterized the thermal properties of these block polymers by DSC and TGA. DSC measurement on the PS-b-P4VP block copolymers exhibited two glass transitions, indicating that the resulting block copolymers are phase separated. Two maxima differential peaks were observed on the TGA trace for the PS-b-P4VP block copolymers might be assigned to the decomposition of the P4VP blocks at 380 ^○C and the PS blocks at higher temperature.     

聚合物/粘土纳米复合材料的热稳定性能和阻燃性能

综述了国内外近年来对蒙脱土的有机改性、聚合物/粘土纳米复合材料的制备以及材料的热性能和阻燃性能等方面应用研究的现状。     

Synthesis of Mineral Nanofiller using Solution Spray Method and its Influence on Mechanical and Thermal Properties of EPDM Nanocomposites

Calcium carbonate (CaCO₃) nanoparticles were synthesized by solution spray of CaCl₂ and NH₄HCO₃ with sodium lauryl sulfate (SLS) as a stabilizing agent. Synthesized nano-CaCO₃ of 20 nm and commercial CaCO₃ (40 mircron) were reinforced in EPDM rubber composites of by varying 2–10 wt% of loading. The rubber nanocomposites were prepared on two roll mill and molded on compression molding machine and were subjected to characterizations like mechanical and thermal. The results were then compared with fly ash (10–60 wt%) filled EPDM rubber composites. It was found that with increase in wt% of nano-CaCO₃ loadings the mechanical and thermal properties of EPDM rubber nanocomposites increases drastically. Improvements in properties were due to uniform dispersion of nano-CaCO₃ into the rubber chain. It means that nano-CaCO₃ gets exfoliated within the rubber chains uniformly. It is also due to fine size of nano-CaCO₃ (20 nm) with uniform transfer of heat during vulcanization, which keeps the rubber chains intact on cross-linking. Results of commercial CaCO₃ and fly ash filled EPDM composites were found to be very inferior over nano-CaCO₃ filled EPDM rubber nanocomposites even though the amount of loading nanofiller was less (2–10 wt% of loading) compared to fly ash of 75 micron (10–60 wt%).     

聚丙烯/四氧化三铁纳米复合材料的制备、表征及磁性能研究

采用固态高速搅拌预混-熔融密炼过程制备了磁性聚丙烯(PP)/四氧化三铁(Fe3O4)纳米复合材料,并分别利用扫描电镜(SEM)、X射线衍射(XRD)、示差扫描量热仪(DSC)、热失重分析仪(TGA)和振动样品磁强计(VSM)对获得的复合材料的形貌、结构及磁性能进行了表征。结果显示:Fe3O4纳米粒子质量分数为5%时在聚合物基体中分散良好,基本呈单颗粒分散;随着Fe3O4含量的增加,粒子在PP基体中团聚程度加剧。Fe3O4和PP在复合材料中保持了各自的晶相结构,但是Fe3O4的加入降低了PP的结晶程度。同时,Fe3O4的加入提高了PP的热稳定性。振动样品磁强计(VSM)的结果表明:复合材料的饱和磁化强度(Ms)随Fe3O4含量的增加而增加,并呈线性的依赖关系;矫顽力(Hc)和剩余磁化强度(Mr)均很小,所制得的磁性纳米复合材料近似呈超顺磁性;该研究为磁性高分子纳米复合材料的制备提供了一种简单易行,Fe3O4纳米粒子在聚合物基体中良好分散,并且可以大批量生产磁性纳米复合材料的方法,并可能促进PP/Fe3O4纳米复合材料在电磁屏蔽和微波吸收等领域的应用。     

Thermal Behavior and Degradation Kinetics of Compatibilized Metallocene-Linear Low Density Polyethylene/Nanoclay Nanocomposites

Morphology, thermal degradation and kinetics of metallocene-linear-low-density polyethylene (m-LLDPE)/m-LLDPE-graft-maleic anhydride (m-LLDPE-g-MA)/nanoclay nanocomposites were compared with m-LLDPE/nanoclay, m-LLDPE-g-MA/nanoclay and m-LLDPE/m-LLDPE-g-MA systems. X-ray diffraction measurements revealed intercalated and “highly intercalated” morphologies for the nanocomposites. Thermogravimetric analysis demonstrated that although thermal degradation of m-LLDPE systems were delayed upon the inclusion of nanoclay in air, an inverse effect was perceived for the nanoclay under inert atmosphere. This conclusion was supported by kinetic analysis in terms of reaction order and activation energy. The results obtained from kinetics models also put forward the contribution of m-LLDPE-g-MA, as a compatibilizer, to the thermal stability enhancement through inter-molecular cross-linking augmentation.     

Nanostructures and nanoporosity in thermoset epoxy blends with an amphiphilic polyisoprene-block-poly(4-vinyl pyridine) reactive diblock copolymer

Nanostructured thermoset blends were prepared based on a bisphenol A-type epoxy resin and an amphiphilic reactive diblock copolymer, namely polyisoprene-block-poly(4-vinyl pyridine) (PI-P4VP). Infrared spectra revealed that the P4VP block of the diblock copolymer reacted with the epoxy monomer. However, the non-reactive hydrophobic PI block of the diblock copolymer formed a separate microphase on the nanoscale. Ozone treatment was used to create nanoporosity in nanostructured epoxy/PI-P4VP blends via selective removal of the PI microphase and lead to nanoporous epoxy thermosets; disordered nanopores with the average diameter of about 60 nm were uniformly distributed in the blend with 50 wt% PI-P4VP. Multi-scale phase separation with a distinctly different morphology was observed at the air/sample interface due to the interfacial effects, whereas only uniform microphase separated morphology at the nanoscale was found in the bulk of the blend.     

蒙脱土结构特性及在聚合物基纳米复合材料中的应用

对蒙脱土的晶层结构、分散性、流变性及表面修饰进行了系统的评述。蒙脱土片层含有Lewis酸点及过渡金属离子可用于烯类单体的催化聚合反应;自从丰田汽车公司使用尼龙 6／粘土纳米复合材料以来,蒙脱土(具有膨润性的粘土)在聚合物基纳米复合材料中的研究和应用正越来越受到世人的关注。对蒙脱土／聚合物纳米复合材料的制备方法及其进展也进行了综述。     

Preparation and Characterization of Ethylene Vinyl Acetate (EVA)/Natural Rubber (SMR L)/Organoclay Nanocomposites: Effect of Blending Sequences and Organoclay Loading

Ethylene vinyl acetate (EVA)/natural rubber (SMR L)/organoclay thermoplastic elastomer nanocomposites were melt compounded in an internal mixer, Haake Rheometer, at 120°C and 50 rpm rotor speed. In this paper, we demonstrate the effect of different blending sequences and organoclay loading from 2 to 10 phr (parts per hundred resins) on the tensile properties, morphology, thermal degradation, flammability, and water absorption behavior of EVA/SMR L/organoclay nanocomposites. EVA/SMR L/organoclay TPE nanocomposites were prepared by three different blending sequences, and each exhibited different tensile properties. Results indicated that the presence of organoclay increases the tensile properties, resistance toward thermal degradation, resistance to water permeation, and flame retardancy for all the nanocomposites prepared via different blending sequences. However, the optimum results for all the properties studied were achieved when EVA was blended with organoclay first and SMR L was incorporated later into the blend. The optimum organoclay loading was achieved at 2 phr. Results from scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies showed that at 2 phr organoclay loading, nanostructures of individual silicate layers were achieved, whereas at 8 phr organoclay loading, agglomeration was observed. Flammability of the nanocomposites decreased when the organoclay loading increased.     

Synthesis and characterization of layer-aligned poly(vinyl alcohol)/graphene nanocomposites

Layer-aligned poly(vinyl alcohol)/graphene nanocomposites in the form of films are prepared by reducing graphite oxide in the polymer matrix in a simple solution processing. X-ray diffractions, scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry and thermogravimetric analysis are used to study the structure and properties of these nanocomposites. The results indicate that graphene is dispersed on a molecular scale and aligned in the poly(vinyl alcohol) (PVA) matrix and there exists strong interfacial interactions between both components mainly by hydrogen bonding, which are responsible for the change of the structures and properties of the PVA/graphene nanocomposites such as the increase in T_g and the decrease in the level of crystallization.