Structure Analysis of PVC Nanocomposites

In this paper poly(vinyl chloride)/clay nanocomposites were prepared by melt intercalation using a single screw extruder. Problems with thermal stability of these nanocomposites during compounding were largely eliminated by pre-treatment of the organoclay with plasticizer (dioctyl phthalate), which created a barrier between polymer and quaternary amine. These nanocomposite materials were analyzed with respect to their morphology. The intercalation, exfoliation, nano-phase dispersion and orientation were investigated using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray diffraction (XRD). Moreover, different types of sample preparation for these techniques were tested as well. It was found that partially intercalated and disordered structure arose in poly (vinyl chloride) composites containing sodium type of montmorillonite, while a fine dispersion of partial to nearly full exfoliation of individual montmorillonite layers in poly (vinyl chloride) matrix was observed when this clay was organically modified. Finally, the influence of different mixing time (in extruder) on nano-phase morphology was surveyed.     

The Monolayer Behavior of Amphiphilic Polymer and Heterostructure of Polymer LB Film/CdS Clusters

In this paper we report the behavior of an amphiphilic polymer monolayer on pure water and Cd2+ subphase. This polymer was composed of hydrophilic ethylene diamine epichlorohydrin slightly crosslinked microgel and hydrophobic stearic chains, noted as ES-1. The introduction of Cd2+ ions in subphase had a marked effect on the process of the organization of the amphiphilic polymer at the air/water interface due to the association of Cd2+ ions with the hydrophilic network, which could be indicated by the pressure-area isotherms and Brewster Angle Microscopy. Ordered ES-1/Cd2+ LB multilayers were fabricated. After the multilayers reacted with H2S gas, CdS clusters were synthesized within the film, which was characterized by X-ray diffraction and UV-visible spectroscopy. Copyright 1999 Academic Press.     

电结晶制Co/Pt多层膜的结构及磁性研究

以单晶Si(111)为基底, 在以P盐[主要成分Pt(NO₂)₂(NH₃)₂]和CoSO₄为主盐的硼酸体系中电结晶Co/Pt多层膜. SEM观察多层膜的断面形貌, 证实多层膜具有周期结构. 经XRD测试, 首次证实了Co-Pt界面上有CoPt₃化合物的存在. 用PPMS测试了多层膜的磁滞回线, 平行于外磁场时膜的矫顽力约为165 Oe, 垂直于外磁场时的矫顽力随Co含量的增加而增加, 最大达到396 Oe. 首次用电结晶方法制得了易磁化轴垂直于膜面的Co/Pt多层膜.     

Multilayer assembly and patterning of poly(p-phenylenevinylene)s via covalent coupling reactions

Poly(p-phenylenevinylene)s with amines and pentafluorophenyl esters on side chains were synthesized and assembled on solid substrates by sequential layer-by-layer (LBL) deposition. This approach enables the creation of robust multilayer thin films via in-situ covalent coupling reactions between successive layers. The buildup of the multilayers was followed by UV/vis absorption spectroscopy and ellipsometry. The observed complex assembly behavior suggests that both covalent and hydrogen-bonding interactions are involved in the formation of multilayer films. The organized structure and surface morphology of resultant multilayers were investigated by reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. This covalent LBL method was further applied to generate conjugated polymer micropatterns using microstamped self-assembled monolayers as templates.     

Electrochemistry of Multilayers of Graphene and Myoglobin Modified Electrode and Its Biosensing

A multilayers of graphene (GR) and myoglobin (Mb) modified electrode was fabricated with a layer of chitosan film. Electrochemical behaviors of the modified electrode were studied by cyclic voltammetry, which exhibited a couple of well‐behaved, stable and quasi‐reversible cathodic and anodic peaks, indicating that Mb realized its direct electron transfer on the biosensor. The experimental result may be accredited to the existence of multilayers conductive GR nanosheets that could provide big specific surface area, fine biological compatibility and ultrahigh electron transfer route for the immobilized Mb. The catalytic reduction peak currents of the biosensor to the detection of trichloroacetic acid were established from 0.6 to 26.0 mM accompanied with the detection limit as 0.15 mM (3σ). Therefore a novel third‐generation mediator‐free electrochemical sensor was successful prepared with the usage of multilayers of GR.     

Structure of self-assembled multilayers prepared from water-soluble polythiophenes

We have studied the structure and morphology of self-assembled polyelectrolyte multilayers prepared using poly(styrenesulfonate) (PSS) and four different cationic poly(alkoxythiophene) derivatives bearing methylimidazolium-terminated ionic side chain at the 3-position of the thiophene ring: poly(1-methyl-3-[3-[3-thienyloxy]-propyl]-1H-imidazolium) (P3TOPIM), poly(1-methyl-3-[6-[3-thienyloxy]-hexyl]-1H-imidazolium) (P3TOHIM), poly(1-methyl-3-[2-[(4-methyl-3-thienyl)oxy]-ethyl]-1H-imidazolium ) (P4Me-3TOEIM), and poly(1-methyl-3-[6-[(4-methyl-3-thienyl)oxy]-hexyl]-1H-imidazolium ) (P4Me-3TOHIM). All the multilayers exhibited regular growth. The thickness of the multilayers was measured with ellipsometry, their layer-by-layer growth was followed by polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and ellipsometry, and the morphology of the films was studied by atomic force microscopy (AFM). The length of the methylimidazolium-terminated side chain (C(n), n = 2, 3, 6) and the substituent (H or Me) at the 4-position of the thiophene ring were varied. All multilayers were inhomogeneous in the sub-micrometer scale and contained aggregates of two kinds. The large ones with a low and constant surface number density were attributed to PSS, whereas the small aggregates were polythiophene-based. The surface density of these organic semiconducting nanoparticles greatly depended on the structure of polythiophene, being favored by polymer regioregularity and the length of the side chain. The side chains remained disordered in all the multilayers, but with polythiophenes having hexyl chains both the imidazolium and thiophene rings tended to orient themselves more perpendicular to the surface than in films containing shorter chains (C2 or C3). The relative water content of the multilayers (at 7.1% relative humidity) did not depend on the film thickness and was the lowest for P4Me-3TOHIM. As the number of bilayers increased the methylimidazolium-sulfonate ion pairs gradually weakened and became more individually hydrated.     

Unusual Multilayered Structures in Poly(ethylene oxide)/Laponite Nanocomposite Films

Summary: The unusual structure of poly(ethylene oxide) (PEO) and Laponite clay in transparent nanocomposite films was investigated using scanning electron, atomic force, and optical microscopy, and X‐ray scattering. Each method is sensitive to different aspects of structural features and together they measure the resulting morphology and shear‐induced orientation. On nanometer length scales, clay platelets were found to orient in bundles while polymer crystallinity was suppressed. Microscopy led to the observation of unexpected and highly oriented multilayers on the micron length scale.

Scanning electron microscopy image of the freeze‐fractured surface of a poly(ethylene oxide)–Laponite film: the view on top of the x–y plane.     

Influence of assembly pH on compression and Ag nanoparticle synthesis of polyelectrolyte multilayers

Influence of assembly pH on compression and Ag nanoparticle synthesis of polyelectrolyte multilayers was studied using poly(diallyldimethylammonium chloride) (PDADMAC) and poly(4-styrenesulfonic acid-co-maleic acid, 1:1SS:MA) sodium salt (PSSMA 1:1) as the building blocks. The thickest multilayers turned out at pH 4. A homogeneous compression by a silicone rubber stamp increased significantly the water contact angle to a same value which was independent on the original assembly pH anymore. The multilayers assembled at pH 4 could be maximumly compressed to a ratio of 70% by a silicone rubber stamp with linear patterns, which was considerably larger than those assembled at other pHs (the compression ratio ~50%). The Ag nanoparticles were then synthesized inside the multilayers either flat compressed or not. The results showed that the compression reduced significantly the amount of Ag nanoparticles for the multilayers assembled at pH 2 and pH 4. The particle amount was also decreased significantly when the multilayers were assembled at higher pH, pH 6, for example, regardless of the compression. Substantial alteration of the multilayers in terms of the surface morphology, thickness and refractive index was found during the reduction of Ag(+) containing multilayers by NaBH(4) solution.     

Adsorption of IgG on/in a PAH/PSS multilayer film: Layer structure and cell response

The binding of immunogloblulins (IgG) (mouse monoclonal recognizing IFNγ) on precoated polystyrene or silica surfaces by the layer-by-layer technique has been investigated with QCM-D and DPI. The aim of the work was to increase the sensitivity of the conventional enzyme-linked immunosorbent spot (ELISpot) assay. The polyelectrolytes used to build the multilayers were poly(allylamine hydrochloride) (PAH)/poly(sodium 4-styrenesulfonate) (PSS) alternately adsorbed from 150mM NaCl. The multilayer build up is linear and the internal structure of the PAH/PSS multilayer is compact and rigid as observed by low relative water content (20-25%) and high layer refractive index (n～1.5) after the formation of five bilayers. Incorporation of IgG within the PAH/PSS multilayer did not give rise to overcharging and did not affect the linear build up. ELISpot test on PAH/PSS multilayer modified polystyrene wells showed that the cytokine response was significantly smaller than on the regular PVDF backed polystyrene wells. This may be due to the compact and rigid nature of the PAH/PSS multilayer, which does not allow formation of the kind of three dimensional support needed to achieve bioactive IgG binding to the surface. Immunological tests of the polyelectrolyte multilayers in the absence of IgG showed that PSS terminated PAH/PSS multilayer did not induce any cytokine response whereas PAH terminated did, which suggests that PSS totally covers the surface from the cells point of view.     

水热法合成Bi2S3纳米管及其生长机理

以硝酸铋[Bi(NO)3]和硫化钠(Na2S)为反应原料, 采用水热法在120 ℃下反应12 h, 制备出Bi2S3纳米管. 利用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、选区电子衍射(SAED)和高分辨透射电镜(HRTEM)对其结构和形貌进行了表征. 结果表明, 所制备的产物是结晶良好的正交相Bi2S3纳米管, 其外径为100~500 nm, 内径为50~200 nm, 长为1~5 μm. 根据实验结果讨论了Bi2S3纳米管的生长机理. 初步研究了反应温度和矿化剂种类对产物形貌和结构的影响.     

The use of etching techniques to investigate the morphology of mechanically induced transformations in an aliphatic polyketone

Existing permanganic etching techniques have been adapted for an aliphatic polyketone terpolymer to examine its spherulitic and lamellar morphology by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). A spherulitic morphology was observed consisting of irregularly shaped spherulites with an average diameter of 5–7 μm and poorly defined spherulite boundaries. Crystalline lamellae were found to be oriented radially within the spherulites. The morphology associated with mechanically induced transformations in a number of deformation systems has been studied and compared to that arising in other common polymeric systems. Changes in morphology through the neck region of drawn samples revealed the elongation of the spherulites as the morphology is transformed from a spherulitic to a fibrillar structure. In samples tested between 23°C and 120°C, radial flaws were observed within the spherulites prior to and within the neck transformation zone. These radial flaws were not observed for samples tested at higher temperatures. Four-point bend tests were conducted on double notched and pre-cracked aliphatic polyketone samples. Examination of the process zone around the crack at the core of the sample revealed crazes characteristic of semicrystalline polymers subjected to a highly constrained stress state. However, the process zone around the crack at the surface of the sample was found to consist of shear bands, suggesting a less constrained damage regime. High cycle fatigue loading also induced flaws oriented radially within the spherulites. Examination of the region around the failure surface in samples fatigue cycled until failure revealed a process consisting of an array of crazes reminiscent to that found in the four-point bend tests. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3246–3255, 1999     

Influence of assembling pH on the stability of poly(L-glutamic acid) and poly(L-lysine) multilayers against urea treatment

Polyelectrolyte multilayers of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) were built up using the layer-by-layer (LbL) technique in low pH (3.6, PM3.6) and in neutral pH (7.4, PM7.4) solutions. The multilayers were then treated with a concentrated urea (one kind of denaturant for proteins and polypeptides) solution (8M) and rinsed with corresponding buffer. The buildup and treatment processes were investigated by ultraviolet visible spectroscopy and ellipsometry. The surface morphology was observed by scanning force microscopy (SFM). The inner structures were determined by X-ray reflectometry and circular dichroism spectroscopy (CD). An exponential growth of the optical mass and the layer thickness was observed for both PM3.6 and PM7.4. After urea treatment, a significant mass loss for PM3.6 was found, while no mass change was recorded for PM7.4. The dominant driving force for PM7.4 is electrostatic interaction, resulting in multilayers with an abundant beta-sheet structure, which has higher stability against urea treatment. By contrast, the dominant driving force for PM3.6 is hydrogen bonding and hydrophobic interaction, which are sensitive to the urea treatment. The mechanism is substantiated by molecular mechanics calculation. This has offered a convenient pathway to mediate the multilayer properties, which is of great importance for potential applications.     

Effect of Cryostructuring Treatment on Some Properties of Xanthan and Karaya Cryogels for Food Applications

Cryogels are novel materials because the manufacturing process known as cryostructuring allows biopolymers to change their properties as a result of repeated controlled freeze–thaw cycles. Hydrogels of xanthan and karaya gums were evaluated after undergoing up to four controlled freeze–thaw cycles in indirect contact with liquid nitrogen (up to −150 °C) to form cryogels. Changes in structural, molecular, rheological, and thermal properties were evaluated and compared to those of their respective hydrogels. Samples were also analyzed by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), Rotational Rheology (RR), Modulated Differential Scanning Calorimetry (MDSC) and zeta potential (ζ). In general, significant differences (p < 0.05) between the numbers of freeze–thaw cycles were found. Karaya cryogels were not stable to repeated cycles of cryostructuring such as the three-cycle xanthan cryogel, which has the best structural order (95.55%), molecular interactions, and thermal stability, which allows the generation of a novel material with improved thermal and structural properties that can be used as an alternative in food preservation.     

Co-gelation mechanism of xanthan and galactomannan

Synergistic gelation of dilute (0.1% total gums) mixed solutions of xanthan and galactomannan isolated from seeds of Delonix regia was investigated. Gelation occurred in a mixed solution of xanthan and galactomannan at 0.1% total gums at room temperature (25 °C). The flow curves of mixed solutions of native xanthan and galactomannan showed plastic behavior. The maximum elastic modulus was obtained when the ratio of the xanthan to galactomannan was 2:1 at room temperature (25 °C). The largest elastic modulus was observed in the mixture solution of deacetylated xanthan. However, a small elastic modulus was obtained in the mixture with depyruvated xanthan. The results obtained supported the interaction mechanism between xanthan and galactomannan (locust bean gum) previously proposed, and the pyruvate methyl groups might also take part in the interaction.     

Influence of chemical treatments on adhesion properties of hemp fibres

In addition to be an environmentally friendly material, hemp fibres are also inexpensive reinforcements in thermoplastics or concrete composites, due to their intrinsic mechanical, thermal and acoustic properties. The morphology of hemp fibres has been chemically modified in order to enhance the matrix/fibre interface and has been examined by Scanning Electron Microscopy (SEM). In this paper, Gas Chromatography (GC) and Atomic Force Microscopy (AFM) were used to investigate the influence of treatments on the composition of hemp fibres and also on the micro-adhesive interactions between a silica colloidal probe and the surface of the fibres using Chemical Force Microscopy (CFM). Microscopy studies and chemical analysis showed that each treatment tends to lead to a morphology of interconnected web-like structure of hemp fibres. It was found that on an average, the adhesion force, contribution of capillary force and Van der Waals' forces, is higher in the case of NaOH treatment.     

Effect of imaging techniques on the observed surface morphology of oxygen plasma etched polyethylene fibres

The present work examined the interactions of Activated Oxygen (AO) and Vacuum UV (VUV) radiation generated by oxygen RF plasma with Ultra-Strong Ultra High Molecular Weight Polyethylene (UHMWPE) fibres. The samples were exposed in the afterglow region, beyond the RF reactor exit. Surface morphology changes were characterized by Atomic Force Microscopy (AFM) in contact and tapping modes and Low-Vacuum (LV) and High-Resolution (HR) Scanning Electron Microscopy (SEM).Simultaneous exposure to AO and VUV caused surface erosion characterized by the formation of ordered domains and a morphological reconstruction into row structure. However, the different imaging techniques showed a variety of morphologies of the same surface depending on the imaging contrast mechanism. An explanation for the origin of these observed morphologies is presented.     

Hybridization of Nafion membranes with an acid functionalised polysiloxane: Effect of morphology on water sorption and proton conductivity

Polysiloxane-modified hybrid Nafion membranes were prepared by casting a mixture of Nafion solution and a precursor of acid functionalised polysiloxane based on tetraethoxysilane and a mercaptan-organoalkoxysilane.Scanning Electron Microscopy (SEM) and Atomic Force Microscopy analysis revealed that the functionalised polysiloxane was dispersed either as finely nanosized inclusions or as coarse domains depending on the rate of the solvent evaporation during the casting procedure. In particular the slower is the rate of solvent evaporation the more interpenetrated and homogenously dispersed at nanosized level is the polysiloxane inside the Nafion membrane.The hybridization process increases the thermal stability of the membranes of about 50 °C relatively to the unmodified Nafion. Small angle X-ray scattering (SAXS) analysis reveals that the hybrid membranes exhibited the typical morphology of Nafion consisting of distinct hydrophilic and hydrophobic domains.Water vapor sorption and proton conductivity were measured varying the temperature (up to 120 °C) and the water activity conditions (from 0.1 to 0.8). The polysiloxane network always increases the water vapor uptake of the membranes and increases significantly the proton conductivity at higher temperature depending on the type of morphology developed by the manufacturing method. In particular hybrid membranes exhibiting nanosized polysiloxane dispersion show a proton conductivity which is up to one-and-half time higher than Nafion recast membrane at high temperature and low water content.     

Layer‐by‐layer assembly of weak‐strong copolymer polyelectrolytes: A route to morphological control of thin films

Multilayer films were assembled from a strong polyelectrolyte (poly(diallyldimethylammonium chloride), PDADMAC) and a copolymer containing both strongly charged styrene sulfonate moieties and weakly charged maleic acid moieties (poly(4‐styrenesulfonic acid‐co‐maleic acid), PSSMA). Growth of PSSMA/PDADMAC multilayers was linear, as characterized by UV‐vis spectroscopy and quartz crystal microgravimetry. The influence of both the pH of the PSSMA adsorption solutions and the ratio of SS:MA in the PSSMA on multilayer properties was investigated. Fourier transform infrared spectroscopy results showed that the ionization of carboxylic acid groups in PSSMA/PDADMAC multilayers did not vary significantly with changes in the PSSMA assembly pH. However, the multilayers showed different thicknesses, surface morphologies, and stability to post‐assembly pH treatment. We also demonstrate that PSSMA/PDADMAC multilayers are significantly more stable than PSSMA/PAH multilayers after post‐assembly pH treatment (i.e. the films remain intact when exposed to pH extremes). In addition, the surface morphology of two films (PSSMA 1:1 assembled at pH 5.8, post‐treated at pH 2 and PSSMA 3:1 assembled at pH 5.8, post‐treated at pH 11) changed significantly when the films were exposed to solutions of different pH and, in the former case, this change in film morphology was reversible. The porous morphology after treatment at pH 2 could be reversed to give a significantly smoother film after subsequent exposure to water for 24 h. Our results demonstrate that by the rational choice of the assembly pH of PSSMA, stable and pH‐responsive films can be obtained via the sequential assembly of PSSMA and PDADMAC. These films have potential in controlled release applications where film stability and pH‐responsive behavior are essential. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4341‐4351, 2007     

Cryo-FIB-Preparation and Cryo-SEM Investigation of Gold Nanolayers Used as Absorber for Laser Welding of Polymer Foils

The morphology of welded polymer foils was investigated by Scanning Electron Microscopy (SEM) using Focused Ion Beam (FIB) technology for cross-sectional preparation. Due to the sensitive structure of the copolymer Ethylene Tetrafluororethylene (ETFE), FIB preparation and SEM investigation were performed at cryo conditions. A gold nanolayer was used as absorber for the laser beam to weld the transparent copolymer foils. The embedding of the gold nanolayer inside the welding seam and its influence on the mechanical stability of the welding seams was demonstrated.     

Monolayer behavior of a rare-earth bisphthalocyanine derivative and determination of its molecular orientation in an LB film

In this paper, the monolayer behavior of a new symmetrically substituted ytterbium bisphthalocyanine derivative Yb-octa-4-(2,4-di-tert-pentylphenoxyl) bis phthalocyanine was investigated, its phase change morphology at the air/water interface was directly observed by Brewster Angle Microscopy (BAM). Its molecular orientation in an LB film was determined by polarized UV–Vis spectra.