Study on the morphology of the hydrophobically‐modified polyelectrolyte in aqueous solution by AFM measurements

This work focuses on the AFM study of the aggregation morphology and association mechanism of the hydrophobically‐association water‐soluble polymer P (AM‐AA‐BPAM) in aqueous solution. It shows that the P (AM‐AA‐BPAM) molecule chain, which has hydrophobic and hydrophilic ionic groups, forms the “spherical” aggregations as micelles below 0.2 g · dL^?1, and then connect each other to form the string‐like aggregations, which produce large viscosity for the polymer solution. It is also coincident with the FCS, DLS, and viscosity study result. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1175–1178, 2004     

AFM Study on the Interactions Across Interfaces Containing Attached Polymer Chains

Summary: Interactions between surfaces with attached polymers are very common in both biological and engineering fields. These types of interactions are critical in processes such as coagulation and flocculation in mineral processing, biological recognition in metabolic processes and stress transference in polymer composites, among others. Although many mechanisms have been proposed to explain phenomena occurring at the interfaces on a molecular level, few experimental procedures can give direct information about them. In this work, interactions occurring at interfaces containing attached polymer chains, such as the ones that are present in polymer composites, were studied by using AFM. In order to identify the effect of the structure of the interface on phenomena such as stress transference and energy dissipation, polymers with different molar mass, areal density and chemical architecture were synthesized and attached to substrates and AFM cantilevers. Force‐distance curves, obtained by AFM, provided some fundamental information about the mechanisms involved when polymers attached to different surfaces interact. Results showed that chains grafted on different surfaces can interact via entanglements and intersegmental bonding. Based upon the application of the AFM modified technique, interfaces containing polymers, such as in polymer composites, can be designed and optimized through the manipulation of its structure to achieve new roles in the performance of systems.

     

Morphology of poly(styrene‐block‐dimethylsiloxane) copolymer films

The morphologies of poly(styrene‐block‐di‐methylsiloxane) (PS‐b‐PDMS) copolymer thin films were analyzed via atomic force microscopy and transition electron microscopy (TEM). The asymmetric copolymer thin films spin‐cast from toluene onto mica presented meshlike structures, which were different from the spherical structures from TEM measurements. The annealing temperature affected the surface morphology of the PS‐b‐PDMS copolymer thin films; the polydimethylsiloxane (PDMS) phases at the surface were increased when the annealing temperature was higher than the PDMS glass‐transition temperature. The morphologies of the PS‐b‐PDMS copolymer thin films were different from solvent to solvent; for thin films spin‐cast from toluene, the polystyrene (PS) phase appeared as pits in the PDMS matrix, whereas the thin films spin‐cast from cyclohexane solutions exhibited an islandlike structure and small, separated PS phases as protrusions over the macroscopically flat surface. The microphase structure of the PS‐b‐PDMS copolymer thin films was also strongly influenced by the different substrates; for an asymmetric block copolymer thin film, the PDMS and PS phases on a silicon substrate presented a lamellar structure parallel to the surface at intervals. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1010–1018, 2007     

AFM study of crystalline cellulose in the cell walls of straw

Crystalline cellulose in the cell walls of straw was studied by atomic force microscopy (AFM). The samples were first treated and then observed by AFM under dimethylsulfoxide (DMSO). The crystalline regions were located and two allomorphs of crystalline cellulose, triclinic I_α and monoclinic I_β phases, were identified. In most crystalline regions, the I_α and I_β phases are intimately associated, with the I_β phase more abundant than the I_α phase. In some small domains only one phase with long‐range order was observed. It was demonstrated that in these one‐phase domains, I_α phase crystals always have their (010) plane lying parallel to the cell wall surface and I_β phase crystals with (110) plane lying parallel. Copyright © 2005 Society of Chemical Industry     

原子力显微镜研究鱼鳞胶原蛋白的溶液聚集行为

用原子力显微镜(AFM)考察了样品质量浓度、溶液pH及温度对鱼鳞胶原蛋白溶液聚集态的影响。结果表明,在pH2.7的醋酸溶液中,当鱼鳞胶原蛋白质量浓度为10μg/mL时,鱼鳞胶原蛋白主要以单体和线性小聚集体形式存在,随着质量浓度继续增大,胶原分子开始自组装形成网状结构,当质量浓度达到4 mg/mL时,形成无规线团结构;而在pH7.2的Tris-HC l溶液中,即使在10μg/mL的低质量浓度下,鱼鳞胶原蛋白也能自组装成不规则的片状聚集体,并通过横向融合形成多孔网状结构。随着质量浓度的增大,纤维直径和高度明显增加;鱼鳞胶原蛋白在40℃处理1 h,其聚集行为发生明显改变,聚集体由线性变为球状;当处理温度升至80℃时,其高级结构基本被破坏,AFM图像上只可见少许不规则分布的团状聚集体。     

Electron holography and AFM studies on styrenic block copolymers and a high impact polystyrene

Many of the artifacts of conventional electron microscopy can be avoided if the unstained polymers are studied by electron holography and atomic force microscopy (AFM). Holograms of thin sections (50–70 nm) of organic block copolymers were recorded, and the corresponding phase images were reconstructed. In this way, typical structures such as lamellae and cylinders could be imaged without any staining. In addition, we successfully recorded holograms and performed Lorentz microscopy of an impact‐modified polystyrene (high‐impact polystyrene). The results were compared with the tapping mode AFM phase images. Electron holography and AFM have been demonstrated as suitable tools to image unstained heterogeneous polymers, leading to the understanding of their structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1573–1583, 2005     

Morphology and fracture properties of modified bisphenol A and novolac type vinyl ester resins

The morphology–toughness relationship of vinyl ester resins was studied as a function of their modification. Bisphenol A based and novolac‐based vinyl ester resins were modified by a star‐shaped polyether polymer with vinyl and hydroxyl functionalities and/or by a polyisocyanate. The polyisocyanate‐containing systems were termed vinyl ester/urethane hybrids. The morphology of the crosslinked resins was studied with dynamic mechanical thermal analysis and atomic force microscopy with ion‐eroded specimens and discussed. The toughness of the crosslinked resins was assessed by the linear elastic fracture mechanics with compact tension specimens. The fracture toughness and energy changed fairly linearly as functions of M_c and M_c^0.5, respectively, where M_c is the mean molecular mass between crosslinks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4012–4022, 2006     

Direct observation of the main cell wall components of straw by atomic force microscopy

Cellulose, hemicellulose, and lignin are the main cell wall components of straw. After removal of the wax and the major portion of lignin, the remaining components of the cell wall surface of straw were determined by atomic force microscopy, which revealed a network structure of cellulose and hemicellulose, and some lignin localized on the surface of the network, consistent with the cell wall model suggested by other researchers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2055–2059, 2003     

Surface nanostructures and dynamic contact angles of functionalized poly(ethylene terephthalate) fibers

An approach (a combination of techniques) to studying poly(ethylene terephthalate) (PET) fibers metal-coated by the sputtering of copper is reported. The effects of copper coatings on the surface morphology, surface chemistry, and surface energy were investigated with atomic force microscopy (AFM), energy-dispersive X-ray (EDX) analysis, and dynamic contact angle measurements. Functional nanostructures formed by sputter coating on the fiber surface were revealed with AFM. The introduction of copper onto the fiber surface was also detected by EDX analysis. The fibers functionalized by the sputter coating resulted in changes in the surface energy measured with the advancing and receding contact angles. Both the advancing and receding contact angles were reduced after sputter coating by copper, but the contact angle hysteresis was significantly increased as the coating was applied. The surface resistivity measurements revealed that sputter coating by copper considerably improved the surface conductivity of the PET fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of N‐β‐aminoethyl‐γ‐aminopropyl polydimethyl‐co‐polydiphenylsiloxane and its film morphology and orientation

A fabric softener, N‐β‐aminoethyl‐γ‐aminopropyl polydimethyl‐co‐polydiphenylsiloxane (PASO), was synthesized by the polymerization of octamethyl cyclotetrasiloxane with an amino‐functional silane and dimethyldiphenylsilane. The chemical structure of the synthesized polysiloxane was characterized by Fourier transform infrared and ¹H‐NMR spectra. The morphology, composition, and hydrophobic properties of the PASO film were investigated by X‐ray photoelectron spectroscopy, atomic force microscopy, contact angle measurement, and other measurements. The experimental results indicate that on the silicon wafer surface, PASO formed a hydrophobic, nonhomogeneous structural film. In addition, the atomic force microscopy results show that the PASO film deposited on the silicon wafer seemed to be slightly rougher than the film of the control, the N‐β‐aminoethyl‐γ‐aminopropyl polydimethylsiloxane. As a result, an orientation model of PASO is proposed on the basis of the characterization of the PASO film properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphology characterization of high‐impact resistant polypropylene using AFM and SALS

Atomic force microscopy and small angle light scattering have been used to characterize the morphology of high‐impact polypropylene. Because of sample preparation requirements, both techniques are relatively simple compared with conventional electron microscopy approaches. Using atomic force microscopy the spatial distribution of the impact‐modifying ethylene‐propylene rubber (EPR) domains could be readily identified whereas small angle light scattering was used to quantify overall domain size distribution. EPR domains from a few hundred nanometers to a few microns in size were observed with average sizes that vary from the edge to the center of the polypropylene particle. In addition, it has been observed that the morphology shifts from discrete domains to bicontinuous as the EPR content is increased. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 452–457, 2000     

AFM measurements of hydrophobic forces between a polyethylene sphere and silanated silica plates- the significance of surface roughness

Recently, substantial research effort has been devoted to the study of non-DLVO forces between hydrophobic surfaces. However, the significance of surface roughness in the analysis of these hydrophobic attractive forces has not been given sufficient consideration and research is now in progress to attend to this issue. Fused silica plates covered with adsorbed octadecyltrichlorosilane (OTS) were characterized by water contact angle measurements and atomic force microscopy (AFM). Surfaces with different surface coverages and different contact angles were obtained by variation of the adsorption time. OTS formed patches on the silica surfaces, the lateral size and height of which depended on the adsorption time. Such surfaces exhibit differences in roughness at the sub-nanometer level. Using the AFM colloidal probe technique, forces between a polyethylene sphere and silanated silica surfaces were measured in water. Long-range attractive forces were found, usually referred to as hydrophobic forces. The resulting force vs. distance curves were fitted with a double exponential function. The magnitude of the short-range part of the force curves seems to correlate with water contact angles at silanated silica surfaces. On the other hand, the range of the long-range force correlates with the roughness of the silanated silica surface. These results with silanated silica surfaces were compared with the AFM results for polyethylene and graphite surfaces and on the basis of these experimental efforts, it appears that the nature of these hydrophobic attractive forces is related to surface roughness.     

Brownian Motion Influence on AFM Exosomes’ Size Measurements

Extracellular vesicles are evaluated by nanoparticle tracking analysis (NTA), providing information on their hydrodynamic diameters, and by atomic force microscopy (AFM) to calculate their geometric diameters. The aim of this study is to explore the influence of Brownian movements in a sample drop and preparation time on imaging-based measurements and to determine the relationship between the geometric and hydrodynamic sizes of the extracellular vesicles measured by the AFM and the NTA, respectively. Exosomes derived from the human prostate cancer cell line PC3 were evaluated by NTA and AFM, and those results were compared with Monte Carlo simulations. The mean size, evaluated by AFM shortly after application on the mica substrate, is less than its real value. It obtains the correct value faster for a thinner sample drop. Fitting the log-normal distribution to the geometric and hydrodynamic diameters leads to the conclusion that the latter could arise from the former by linear scaling by a factor that could be used to characterize the analyzed extracellular vesicles. The size of the vesicles attached to the mica substrate depends on time. The effect of Brownian motion and stretch of the lipid bilayer should be considered in the context of exosome AFM studies.     

Thermal stability and crystalline of electrospun polyamide 6/organo‐montmorillonite nanofibers

This research is mainly to investigate the thermal and crystalline differences between polyamide 6/montmorillonite (PA6/MMT) and polyamide 6/organo‐montmorillonite (PA6/O‐MMT) nanofibers, which were both prepared by electrospinning under the same process conditions. The structures of PA6/MMT and PA6/O‐MMT nanofibers were observed by scanning electrical microscope. It was identified that the interval between O‐MMT clays was increased in the PA6 matrix compared to that of MMT, which was detected by X‐ray diffraction (XRD). The thermal properties of PA6 nanofibers contained O‐MMT particles were more efficient than PA6/MMT nanofibers, that was verified using thermal gravimetric analysis. The crystalline properties of the electrospun nanofibers was investigated using differential scanning calorimeter and it was found that the degree of crystallinity in the PA6 nanofibers loaded with O‐MMT was much higher than PA6/MMT and PA6 nanofibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,structure, and properties of new methacrylic derivatives of naphthalene‐2,3‐diol

The synthesis of a new monomer, 2,3‐(2‐hydroxy‐3‐methacryloyloxypropoxy)naphthalene, and its copolymerization with divinylbenzene is presented. This monomer was obtained from naphthalene‐2,3‐diol in a two‐step synthesis. Copolymers in the form of porous microspheres were prepared by a suspension‐emulsion polymerization method. As pore‐forming diluents, toluene, 1‐decanol, benzyl alcohol, and their mixtures were used. In studies of their porous structure, two methods were used: the adsorption of nitrogen at low temperatures, which provided information about the porous structure of the material in a dry state, and inverse exclusion chromatography, which provided information about the porous structure of the polymer swollen by a good solvent. The obtained results suggest that the porous structures for the dry and swollen polymers were different. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1886–1895, 2006     

Structure–property relationships of thermoplastic polyurethane elastomers based on polycarbonate diols

The phase-separation behavior and morphology of polycarbonate-based polyurethanes were investigated as a function of the soft-segment molecular weight and chemical structure and the 4,4′-diphenylmethane diisocyanate/1,4-butanediol based hard-segment contents. Polarized optical microscopy and atomic force microscopy images showed that the surface morphologies changed as the soft-segment molecular weight and hard-segment content varied and also when the sample preparation conditions were modified. An increase in the soft- and hard-segment lengths led to increased phase separation with respect to the lower molecular weight soft segment, and this showed an interlocked and connected morphology of intermixed soft and hard domains. The surface morphology of phase-separated polyurethanes with hard segments composed of more than four to five 4,4′-diphenylmethane diisocyanate units contained globular hard-segment domains formed by spherulites, in which the size and connectivity between the branched lamellae changed with the hard-segment size. Interlamellar areas related to the soft segment were seen in the spherulites. Variations in the hard-segment spherulites were observed for polyurethanes based on soft segments of different molecular weights. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Optimization of the electron‐beam‐lithography parameters for the moth‐eye effects of an antireflection matrix structure

In this study, we mainly used the characteristics of electron‐beam lithography in measurement control and direct‐write technology to improve the physical restrictions and production processes of optical lithography and other nanopattern production methods. We did this by using a silicon wafer as a substrate, coating a negative‐tone photoresist, and using scattering and the reflection produced by the collision of an electron beam with the wafer lattice and the proximity effect of a secondary electron inside the electron‐beam photoresist to produce an antireflection matrix structure with a moth‐eye effect. In addition, we used the Taguchi quality method with an orthogonal array to plan the experiment and the signal‐to‐noise ratio to analyze the experimental data, and in the experimental process, we produced a full factorial equivalent experiment, using very few experiment repetitions and deriving optimum conditions. Also, we used back‐propagation neural networks to fine‐tune significant factors, allowing the production of the deepest process control parameters and thereby imparting to the antireflection matrix structure the best effect. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5303–5313, 2006     

Fabrication of a model cellulose surface from straw with an aqueous sodium hydroxide/thiourea solution

Model cellulose surfaces were prepared with both microcrystalline cellulose and cellulose isolated from wheat straw with different molecular weights. A sodium hydroxide/thiourea aqueous solution, instead of any organic solvents, worked as the solvent for dissolving cellulose, and model cellulose films were prepared by a two‐step method: first, the cellulose solution was deposited onto the surface of the substrate with the spin‐coating method, and second, the as‐prepared film was washed with deionized water to remove the impurities and was formed with a flattened surface. Atomic force microscopy was used to measure the morphology, surface roughness, and thickness of the cellulose thin films. X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectrometry were used to characterize the surface chemical information of the films. The results revealed that model cellulose surfaces could form from both kinds of cellulose. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Surface morphology and nodule formation mechanism of cellulose acetate membranes by atomic force microscopy

By the use of atomic force microscopy (AFM), formation mechanism of nodular structure in cellulose acetate membranes was systematically investigated. Elementary factors affecting the nodule formation were delineated on the basis of both kinetic and thermodynamic considerations. It was shown that (1) the exact nature of nodular structure is thermodynamic equilibrium glassy state; nodular structure will vanish in the rubbery state; (2) the thermodynamic factor affecting nodule formation is the membrane formation temperature; with the membrane formation temperature decreasing, more chain segments are able to form nodular structures; (3) nodule formation is dependent on the segment rearrangement; variation of the solvent environment is the major kinetic factor affecting the segment rearrangement and nodule formation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1328–1335, 2003     

Does morphology stick? Tailored particle morphologies by swelling polymerization process

Structured dispersion particles suitable for pressure sensitive adhesives (PSA) were synthesized via swelling polymerization technique (EP 359562). Particles consisting of poly(n‐butyl acrylate) copolymerized with different types of carboxylic acids were used as seeds. The final particles were synthesized by swelling polymerization process, using 6 wt % styrene or 6 wt % methyl methacylate. The resulting particle morphology was analyzed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). From previous works (Coll Surf A 2001, 183–185, 725–737; J Appl Polym Sci 2004, 91, 2610–2623) where two‐step emulsion polymerization was used on similar particles, it is expected that the particle morphology is affected by the polarity of the monomer used for swelling polymerization because of the phase compatibility (thermodynamic parameter). In this work, the seed particles used were always of a glass transition temperature (T_g) below polymerization temperature. The diffusion of the growing polymer chains from the swelling polymerization is therefore mainly affected by their own T_g and the influence of the carboxy groups on the chain length of the entering radicals (kinetic parameter). The different morphologies of the single particles are discussed qualitatively. The effects of reaction parameters are compared with the results given in the previous work. The structure of the corresponding dispersion films was characterized using AFM. Correlations to macroscopic properties such as the cohesive strength and peel adhesion to different substrates are discussed. The results are also compared with the application properties of the corresponding unmodified particles, statistical copolymers, and to blends with small sized PMMA or PS particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1444–1455, 2006