Biopolymer/montmorillonite nanocomposite: preparation, drug-controlled release property and cytotoxicity

In order to combine the advantages of a biopolymer with clay in a drug delivery system, the hot intercalation technique was used to prepare quaternized chitosan/montmorillonite (HTCC/MMT) nanocomposites. Transmission electron microscopy (TEM), x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) results revealed that HTCC chains entered into the interlayer of MMT, and the interaction between them has taken place. This is the basis of the advantage combination. Then the HTCC/MMT nanocomposites were modified to prepare the nanoparticles, whose drug-controlled release behaviours were evaluated. The results suggested that, compared to pure HTCC nanoparticles, certain montmorillonite loadings on quaternized chitosan enhanced the drug encapsulation efficiency of the nanoparticles and slowed the drug release from the nanocomposites. Finally, a study of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) indicated that the nanocomposites are not cytotoxic. Therefore, the HTCC/MMT nanocomposites are of great potential in the biomedical field.     

Mechanical and thermal behavior of non-crimp glass fiber reinforced layered clay/epoxy nanocomposites

Mechanical and thermal properties of non-crimp glass fiber reinforced clay/epoxy nanocomposites were investigated. Clay/epoxy nanocomposite systems were prepared to use as the matrix material for composite laminates. X-ray diffraction results obtained from natural and modified clays indicated that intergallery spacing of the layered clay increases with surface treatment. Tensile tests indicated that clay loading has minor effect on the tensile properties. Flexural properties of laminates were improved by clay addition due to the improved interface between glass fibers and epoxy. Differential scanning calorimetry (DSC) results showed that the modified clay particles affected the glass transition temperatures (T_g) of the nanocomposites. Incorporation of surface treated clay particles increased the dynamic mechanical properties of nanocomposite laminates. It was found that the flame resistance of composites was improved significantly by clay addition into the epoxy matrix.     

Effects of modified and non-modified clay on the rheological behavior of high density polyethylene

HDPE nanocomposites containing 2.5, 5 and 10 wt.% of non-modified and modified clays (NMC and MC) were prepared by melt extrusion in a twin screw extruder. Compression molded samples were prepared. Transmission electron microscopy (TEM) indicated a partial intercalation of the modified clay nanofiller within the HDPE matrix comparing to that of non-modified clay. The moduli of nanocomposites increased with increase in nanofiller concentration; but this increase was greater in the low frequency region. The non-modified clay had a greater increase in the elastic behavior, while the modified clay increased viscose behavior because of more interactions with the matrix and partial intercalation. The rheological behaviors of both HDPE/NMC and HDPE/MC nanocomposites are more sensitive to nanoparticles’ concentration at low frequencies. The HDPE/MC nanocomposites showed semi-circle shapes comparing to HDPE/NMC nanocomposites. While the Cole–Cole plot of HDPE/NMC nanocomposite had more departure of semi-circle shape. The agglomerated particles could concentrate the imposed stress so the yield stress reached at lower shear rates comparing to pure HDPE and HDPE filled 2.5 wt.% NMC nanocomposite. Study of suspension models showed that the Eilers-Van Dijck and Einsten models fitted to almost experimental data satisfactorily.     

Improving the mechanical properties of thermoplastic starch/poly(vinyl alcohol)/clay nanocomposites

Thermoplastic starch/poly(vinyl alcohol) (PVOH)/clay nanocomposites, exhibiting the intercalated and exfoliated structures, were prepared via melt extrusion method. The effects of clay cation, water, PVOH and clay contents on clay intercalation and mechanical properties of nanocomposites were investigated. The experiments were carried out according to the Taguchi experimental design method. Montmorillonite (MMT) with three types of cation or modifier (Na⁺, alkyl ammonium ion, and citric acid) was examined. The prepared nanocomposites with modified montmorillonite indicated a mechanical improvement in the properties in comparison with pristine MMT. It was also observed that increases in tensile strength and modulus would be attained for nanocomposite samples with 10%, 5% and 4% (by weight) of water, PVOH and clay loading, respectively. The clay intercalation was examined by X-ray diffraction (XRD) patterns. The chemical structure and morphology of the optimum sample was also probed by FTIR spectroscopy and transmission electron microscopy (TEM).     

壳聚糖季铵盐/有机累托石纳米复合材料的抗菌性能研究

合成了壳聚糖季铵盐, 并通过溶液插层法将其插层进入有机累托石层间制备纳米复合材料, 研究表明, 当壳聚糖季铵盐与有机累托石的质量比为2∶1时, 其获得了4.8nm的最大层间距. 抗菌结果显示, 在偏酸、中性及偏碱性条件下, 所有的纳米复合材料都具有较好的抗菌性能, 且与有机累托石的含量和层间距成正比. 与壳聚糖季铵盐及有机累托石相比, 纳米复合材料对革兰氏阳性菌、革兰氏阴性菌及真菌的抗菌性能大大提高, 对金黄色葡萄球菌和枯草芽孢杆菌的最小抑制浓度仅为0.00313% (W/V), 且能在30min内杀死90%以上的金黄色葡萄球菌, 80%以上的大肠杆菌. 最后, 通过TEM和SEM结果探讨了其抗菌机理.     

Biodegradable aliphatic polyester-poly (epichlorohydrin) blend/organoclay nanocomposites; synthesis and rheological characterization

Polymer/organoclay nanocomposite systems were prepared from biodegradable aliphatic polyester (BAP)-poly(epichlorohydrin) (PECH) blends via the solvent casting method. From X-ray diffraction analysis, it was confirmed that the increased interlayer distance of the clay was solely affected by the BAP, implying that the BAP has better affinity to clay than PECH in a competitive intercalation mechanism. To clarify the sole effect of clay on polymer blend nanocomposite systems, we fixed the clay content at 3 wt%. The mechanical properties and rheological characteristics in steady and oscillatory shear modes of BAP-PECH/clay nanocomposites were investigated and compared with those of BAP-PECH blends without clay.     

累托石纳米晶层的高压剥离研究

首次采用物理方法高压制备了酚醛树脂(PF)/累托石(REC)粘土和酚醛树脂(PF)/有机改性累托石(OREC)粘土纳米复合材料,以X射线衍射(XRD)、透射电子显微镜(TEM)及红外光谱(IR)分析了复合材料的物相和显微结构。结果表明,不通过层间高分子聚合反应,在常温高压下,由聚合物分子插入粘土层间,可以形成剥离型树脂/粘土纳米复合材料。在100M Pa和500M Pa下,复合材料中的OREC完全剥离,而REC只有部分被剥离。     

Preparation of polystyrene–clay nanocomposite by solution intercalation technique

Polymer–clay nanocomposites of commercial polystyrene (PS) and clay laponite were prepared via solution intercalation technique. Laponite was modified suitably with the well known cationic surfactant cetyltrimethyl ammonium bromide by ion-exchange reaction to render laponite miscible with hydrophobic PS. X-ray diffraction analysis in combination with scanning electron microscopy gives an idea of structural and morphological information of PS–laponite nanocomposite for different varying organo-laponite contents. Intercalation of PS chain occurs into the interlayer spacings of laponite for low organo-laponite concentration in the PS–O-laponite mixture. However, aggregation and agglomeration occur at higher clay concentration. The molecular bond vibrational profile of laponite as well as PS–laponite nanocomposite have been explored by Fourier transform infrared spectroscopy. Thermogravimetric analysis along with differential scanning calorimetry results reveal the enhancement of both thermal stability and glass transition temperature of PS due to the incorporation of clay platelets.     

A quantitative study of the morphology of montmorillonite filled thermosets based on a tailor made homogenisation model

Thermoset/montmorillonite nanocomposites were fabricated and their elastic modulus was measured using experimental modal analysis. The morphology of the nanocomposite was considered as a distribution of several components: exfoliated clay platelets, intercalated clay layers, primary particles and clay agglomerates. A novel homogenisation model, which involves a five-phase sequence based on the Halpin–Tsai equations, was developed to calculate the elastic modulus of the nanocomposites. This model was then used to quantify the morphology of the nanocomposites by back calculating the exfoliation, intercalation and agglomeration fractions from the measured values of the elastic modulus. Additionally, this approach led to quantify the efficiency of the fabrication process, which proved to be optimal for 2.5% clay content.     

Elastomeric epoxy nanocomposites: Nanostructure and properties

In polymer layered silicate nanocomposites, significant differences have been reported between the effects of the nano-reinforcement on rigid and elastomeric nanocomposites. In this paper, we have studied elastomeric nanocomposites based upon DGEBA epoxy resin filled with montmorillonite (MMT) and cured with a long-chain polyoxypropylene diamine, for comparison with analogous rigid nanocomposites. Ultrasonic mixing was used to disperse the MMT in the matrix to improve homogeneity and decrease the agglomerate size. Two different methods of nanocomposite preparation were used in which the MMT was first swollen with either the curing agent or the epoxy before the addition of, respectively, DGEBA or diamine. A better dispersion of the nanoclay in the matrix and a greater amount of intercalation occurred when the MMT was first swollen with the diamine. The effect of MMT concentrations up to 8 wt.% on the mechanical behaviour of the epoxy/MMT nanocomposites was investigated. It was found that the addition of MMT increased the tensile strength and modulus, although SAXS and TEM indicated that a significant fraction of the clay layers were not exfoliated. Nevertheless, the addition of the clay resulted in changes in the fracture surfaces, as indicated by SEM, consistent with the tensile results and indicative of toughening.     

The effect of process parameters on physical and mechanical properties of commercial low density polyethylene/ORG-MMT nanocomposites

Polyethylene/organo-montmorillonite clay (org-MMT) nanocomposites were prepared utilizing PP-g-MA as a compatibilizer by melt intercalation method. In order to increase the miscibility of polyethylene (PE) with nanoparticle surface at firs, a primary masterbatch consist of compatibilizer and org-MMT was prepared then, this compound was melt intercalated with PE to synthesis the PE/org-MMT nanocomposites. In this study, the presence of commercial low density polyethylene in Nanocomposites structure and also the effect of process parameters such as: amount of nanoparticles, mixing rate and mixing time on nanocomposite structure and properties have been investigated. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results showed that the interlayer distance of nanoparticle layers increased and a partially intercalated structure was prepared by melt intercalation method. Interaction between polyethylene chains and nanoparticle layers could be improved if the control of above parameters causes to penetrate the chains into nanoclay layers; by an optimization, this effect could improve the physical and mechanical properties. The DSC data revealed that melting temperature has slowly increased and crystalinity has lightly decreased. Consequently we can claim the thermal properties of LDPE/clay nanocomposite did not considerably change with clay content. A rise in the mechanical properties such as yield stress and modulus was observed by tension test; by addition of 5% clay content the tensile strength increased about 7%, the tensile modulus enhanced about 60% and the yield stress increased about 16% in comparison with the pure LDPE.     

Viscoelasticity and relaxation characteristics of polystyrene/clay nanocomposite

Polymer nanocomposites based on an organophilically modified montmorillonite (OMMT) and polystyrene (PS) are prepared via a solvent casting method using chloroform as a cosolvent to examine their dynamic viscoelastic and relaxation properties, in which the increased basal spacings of the OMMT determined by X-ray diffraction indicated the intercalation of PS chains into OMMT interlayer. From the measured viscoelastic properties originated from the nanocomposite interaction between polymer and OMMT, we were able to determine the characteristic behavior of PS/OMMT nanocomposites. Storage and loss moduli are found to give the transition from liquid-like to solid-like behavior as the clay content increases, especially in the low frequency region. Stress relaxation behavior was also enhanced by showing more solid-like characteristics with increasing OMMT.     

Development of a novel nanocomposite consisting of 3-(4-methoxyphenyl)propionic acid and magnesium layered hydroxide for controlled-release formulation

ABSTRACT

Magnesium layered hydroxide (MLH) intercalated with anionic 3-(4-methoxyphenyl)propionic acid (MPP) was synthesised by a direct reaction method using magnesium oxide and MPP as precursors. A further coating of chitosan was applied on the external surface of MLH–MPP nanocomposite to form a new material, named MLH–MPP/chitosan nanocomposite. The XRD pattern showed an intense and sharp peak at basal spacing 18.9 Å, proving that MPP anions were successfully intercalated into the interlayer gallery of MLH in a monolayer arrangement. The XRD pattern of the MLH–MPP/chitosan nanocomposite shows similar peaks with the MLH–MPP nanocomposite. The result was also supported by FTIR spectra and elemental analysis. TGA/DTG spectra showed that the thermal stabilities of the guest anion in the both nanocomposites were markedly enhanced. A controlled-release study of the MPP ion from the MLH–MPP/chitosan nanocomposite showed a slower release compared to MLH–MPP nanocomposite with an initial rapid release and slow release thereafter. Meanwhile, the release behaviours of MPP ions from both nanocomposites were governed by pseudo-second order kinetics. This result highlights the potential of the nanocomposite as an encapsulated material for the controlled-release formulation of MPP anions.     

累托石/聚合物纳米复合材料的新进展

累托石是我国湖北省盛产的铝硅酸盐矿物, 其与蒙脱土极为相似, 但又具有它独特的结构特点, 近年来广泛用于聚合物/层状硅酸盐纳米复合材料的制备. 本文介绍了累托石的结构特性、表面修饰和累托石/聚合物纳米复合材料的结构及制备方法, 总结了累托石/壳聚糖基纳米复合材料及其作为抗菌剂、吸附剂、药物控释材料和基因载体等功能化应用方面的最新研究成果, 并提出了累托石/聚合物纳米复合材料未来的研究方向.     

Preparation and tribological performance of chemically-modified reduced graphene oxide/polyacrylonitrile composites

Interface control and dispersion of graphene base nanomaterials in polymer matrix are challenging to develop high comprehensive nanocomposites due to their strong interlayer cohesive energy and chemical inertia. In this research, an efficient approach is presented to functionalize reduced graphene oxide nanosheets by N-[3-(trimethoxylsilyl)propyl]ethylenediamine, which is dispersed into polyacrylonitrile to prepare N-[3-(trimethoxylsilyl)propyl]ethylenediamine – reduced graphene oxide/polyacrylonitrile nanocomposites. A thermogravimetric analysis technique was employed to evaluate thermal properties of the nanocomposites. The tribological properties of the polyacrylonitrile/graphene nanocomposites were investigated. The morphologies and volume of the worn surface were examined using a 3D profilometer. The impact of loading ratio on friction coefficient, carry-bearing capacity and durability were studied. The N-[3-(trimethoxylsilyl)propyl]ethylenediamine – reduced graphene oxide/polyacrylonitrile nanocomposite with appropriate loading ratio of reduced graphene oxide exhibited a high load-bearing capacity and durability. Therefore, the polyacrylonitrile/graphene nanocomposite shows promising potential to industrial applications involving the lubrication and anti-wear.     

Morphology,rheology and mechanical properties of polypropylene/ethylene–octene copolymer/clay nanocomposites: Effects of the compatibilizer

The objective of this study was to investigate the effects of two compatibilizers, namely maleated polypropylene (PP-g-MA) and maleic anhydride grafted poly (ethylene-co-octene) (EOC-g-MA), on the morphology and thus properties of ternary nanocomposites of polypropylene (PP)/ethylene–octene copolymer (EOC)/clay nanocomposite. In this regard the nanocomposites and their neat polymer blend counterparts were processed twice using a twin screw extruder. X-ray diffraction, transmission electron microscopy, Energy dispersive X-ray spectroscopy, and scanning electron microscopy were utilized to characterize nanostructure and microstructure besides mechanical and rheological behaviors of the nanocomposites. Clay with intercalated structure was observed in EOC phase of the PP/EOC/clay nanocomposite. Better dispersion state of the intercalated clay in EOC phase was observed by adding EOC-g-MA as a compatibilizer. On the other hand, adding PP-g-MA resulted in migration of the intercalated clay from the EOC to the PP and to the interface regions. It was also demonstrated that the elastomer particles became smaller in size where clay was present. The finest and the most uniform morphology was found in the PP/EOC/clay nanocomposite. In addition, the rheological results illustrated a higher complex viscosity and storage modulus for PP/EOC/PP-g-MA/clay nanocomposite in which clay particles were present in the matrix. Mechanical assessments showed improvements in the toughness of the nanocomposites with respect to their neat blends, without significant change in stiffness and tensile strength values. These results highlight a toughening role of clay in the polymer blend nanocomposites studied.     

Low density polyethylene – Chitosan composites

With the aim of develop new materials for active food packaging, composites of low-density polyethylene (LDPE) with chitosan (CS) or chitosan sodium montmorillonite clay nanocomposites (CSnano), with or without Irganox 1076 commercial synthetic antioxidant or vitamin E (VE) as natural antioxidant were prepared by melt processing. The obtained materials have been characterized by processing behavior, mechanical and thermal properties, positive groups determination, atomic force microscopy and standard tests to assess antimicrobial and antioxidant activities. The compositions assuring insignificant decrease in mechanical and thermal properties were selected as LDPE/3CSnano/VE and LDPE/6CSnano/VE. It has been shown the chitosan imparts antimicrobial properties to LDPE films while the vitamin E increased the oxidation induction period, especially for materials containing chitosan nanocomposites. The incorporation of both chitosan nanocomposites and vitamin E in polyethylene gave films with good antimicrobial and thermal properties because of significant increase of charge surface and important changes in surface topology and antimicrobial activity because of a synergistic effect. The nanocomposites cannot only passively protect the food against environmental factors, but they may enhance shelf life of food products.     

Thermal properties of PMMA/montmorillonite clay nanocomposites

Polymer/Clay offer tremendous improvement in wide range of physical and engineering properties for polymers with low filler loading. In nanotechnology polymer/clay nanocomposites use smectitetype clays that have layered structures. In this work, Poly (methyl methacrylate) (PMMA) was synthesized by free radical addition polymerization in the presence of high power ultrasound. The Poly (methyl methacrylate) (PMMA)-Montmorillonite (MMT) clay nanocomposites were synthesized by two different techniques viz., ultrasonic mixing and magnetic stirring. An analysis of the XRD data confirms that the composites are in the nanometer scale. The FTIR spectra show that there is strong interaction between the clay and the polymer that enhances the thermal stability. The thermal stability of the experimental nanocomposite prepared by the two processes is compared. Further analysis of XRD data shows that intercalation as well as exfoliation has taken place in both the types of nanocomposites preparation. An analysis of the TG, DTG curves reveal that the thermal stability is found to increase by nearly 30% for ultrasonic mixing than that of magnetic stirring.     

Long-term and controlled release of chlorhexidine–copper(II) from organically modified montmorillonite (OMMT) nanocomposites

Drug/metal ion complexes exhibit improved antimicrobial activity and intercalating the above complexes into the interlayer of clay endows a long-term and controlled-release behavior. In this study, chlorhexidine was first complexed with copper (II) ion and then intercalated into the interlayer of MMT to form chlorhexidine–copper (II)/montmorillonite (CHX–Cu/MMT) nanocomposites. The nanocomposites were characterized with Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). A nearly lateral-monolayer arrangement of CHX–Cu was supposed for the intercalation. Release kinetics indicated that the release process satisfied a pseudo-second-order mode. The antibacterial results showed that the CHX–Cu/MMT composites had long-term and controlled-release behavior.     

铬簇合物及铬铝交联蒙脱石纳米复合材料的形成

利用XRD、IR、DTA、比表面和吸氨量等方法研究2:1型的蒙脱石粘土矿物和铬簇合物[Cr₃O(OOCCH₃)₆(OH₂)₃]Cl·6H₂O(简记为CrC)交联剂的层间交联作用,并对铬铝交联蒙脱石纳米复合材料的制备方法、影响因素和性质作初步探讨.结果表明,交联剂分子种类、大小和Cr/Al比值对材料的层间距大小有十分重要的影响;而材料层间距大小、交联剂CrC/土的比例和Cr/Al比值则是影响材料的表面性质和热稳定性的重要因素.