Morphological change of crystalline polymer films by annealing: substrate‐ and heating/cooling‐rate‐dependent surface roughness

We study the morphological change of crystalline polymer films by annealing using atomic force microscope, X‐ray diffraction, and Fourier transform infrared spectroscopy techniques. As typical samples, we employ high‐density and low‐density polyethylene films prepared by the cast method. After annealing at 135 °C for 4 h, the surface roughness of polyethylene films by the atomic force microscope significantly increases, and the crystallite size by the X‐ray diffraction also shows some increase, while the Fourier transform infrared spectroscopy spectrum hardly exhibits any change. This can be well explained as a result of the growth of crystal structure by recrystallization during annealing. More interestingly, we find that the choice of the substrate and also the heating/cooling rates for annealing significantly influences the surface roughness of the films. Copyright © 2017 John Wiley & Sons, Ltd.     

Differentiation of 18O‐ and 16O‐rich layers in anodic alumina films by glow discharge time‐of‐flight mass spectroscopy

The performance of glow discharge time‐of‐flight mass spectrometry in isotopic differentiation is revealed using the distribution of oxygen isotopes ¹⁶O and ¹⁸O in barrier‐type anodic alumina films as a focus. Anodic alumina films comprising ¹⁸O‐rich layers of controlled thickness were formed by the appropriate combination of anodising of superpure aluminium in electrolytes enriched with ¹⁸O isotopes and of natural abundance of ¹⁸O isotopes. Analysis of the elemental depth profiles of selected ionic species, i.e. ¹⁶O¹⁸O, allowed determination of the locations of the ¹⁸O‐rich layers and the ¹⁸O/¹⁶O interface. Copyright © 2010 John Wiley & Sons, Ltd.     

Effects of bias voltage on structure and properties of TiAl‐doped a‐C:H films prepared by magnetron sputtering

Hydrogenated TiAl‐doped a‐C:H films were deposited on Si substrates by middle frequency magnetron sputtering TiAl target in argon and methane gas mixture atmosphere. Effects of substrate bias voltage on structure and properties of the films, such as the surface morphology, hardness, chemical nature and bond types, were investigated by means of atomic force microscopy (AFM), XPS, Raman spectroscopy and nanoindentation. The friction and wear behaviors of the deposited films were characterized on an UMT‐2MT tribometer. SEM was utilized to analyze the wear scar on steel balls and debris after sliding on the deposited films under dry friction conditions. The results demonstrated that the film deposited at ? 100 V exhibited low friction coefficient which is attributed to the easier formation of graphitized transfer layer. Copyright © 2010 John Wiley & Sons, Ltd.     

Ion‐beam‐induced morphology on the surface of thin polymer films at low current density and high ion fluence

The effect of Xe⁺ bombardment on the surface morphology of four different polymers, polystyrene (PS), poly(phenylene oxide), polyisobutylene, and polydimethylsiloxane, was investigated in ion energy and fluence ranges of interest for secondary ion mass spectrometry depth‐profiling analysis. Atomic force microscopy (AFM) was applied to analyze the surface topography of pristine and irradiated polymers. AFM analyses of nonirradiated polymer films showed a feature‐free surface with different smoothness. We studied the influence of different Xe⁺ beam parameters, including the incidence angle, ion energy (660–4000 eV), current density (0.5 × 10² to 8.7 × 10² nA/cm²), and ion fluence (4 × 10¹⁴ to 2 × 10¹⁷ ion/cm²). Xe⁺ bombardment of PS with 3–4 keV at a high current density did not induce any change in the surface morphology. Similarly, for ion irradiation with lower energy, no surface morphology change was found with a current density higher than 2.6 × 10² nA/cm² and an ion fluence up to 4 × 10¹⁶ ion/cm². However, Xe⁺ irradiation with a lower current density and a higher ion fluence led to topography development for all of the polymers. The roughness of the polymer surface increased, and well‐defined patterns appeared. The surface roughness increased with ion irradiation fluence and with the decrease of the current density. A pattern orientation along the beam direction was visible for inclined incidence between 15° and 45° with respect to the surface normal. Orientation was not seen at normal incidence. The surface topography development could be explained on the basis of the balance between surface damage and sputtering induced by the primary ion beam and redeposition–adsorption from the gas phase. Time‐of‐flight secondary ion mass spectrometry analyses of irradiated PS showed strong surface modifications of the molecular structure and the presence of new material. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 314–325, 2001     

Comparative study on structure and properties of titanium/silicon mono‐ and co‐doped amorphous carbon films deposited by mid‐frequency magnetron sputtering

The titanium/silicon mono‐ and co‐doped amorphous carbon films were deposited by mid‐frequency magnetron sputtering Ti target, Si target, and Ti80S20 alloy target, respectively. The effects of doped elements on the composition, surface morphology, microstructure, and mechanical and tribological properties of the films were investigated. The results reveal that the ratio of sp³ and sp² carbon bonds of the films is regulated between 0.28 and 0.62 by a combination of Ti and Si dopant. The addition of small amounts of silicon leads to an increase in sp³ bonds and disorder degree of the sp² carbon. The co‐doped film exhibits significantly superior friction performance than the mono‐doped films. The ultra‐low friction (μ < 0.01) was achieved under a load of 2 N in ambient air with 40% RH. By comparing to the mono‐and co‐doped films, it is thought that the sp³/sp² ratio of the films may play a key role for the superlow friction. Copyright © 2013 John Wiley & Sons, Ltd.     

Topological “interfacial” polymer chemistry: Dependency of polymer “shape” on surface morphology and stability of layer structures when heating organized molecular films of cyclic and linear block copolymers of n‐butyl acrylate‐ethylene oxide

The “topological polymer chemistry” of amphiphilic linear and cyclic block copolymers at an air/water interface was investigated. A cyclic copolymer and two linear copolymers (AB‐type diblock and ABA‐type triblock copolymers) synthesized from the same monomers were used in this study. Relatively stable monolayers of these three copolymers were observed to form at an air/water interface. Similar condensed‐phase temperature‐dependent behaviors were observed in surface pressure–area isotherms for these three monolayers. Molecular orientations at the air/water interface for the two linear block copolymers were similar to that of the cyclic block copolymer. Atomic force microscopic observations of transferred films for the three polymer types revealed the formation of monolayers with very similar morphologies at the mesoscopic scale at room temperature and constant compression speed. ABA‐type triblock linear copolymers adopted a fiber‐like surface morphology via two‐dimensional crystallization at low compression speeds. In contrast, the cyclic block copolymer formed a shapeless domain. Temperature‐controlled out‐of‐plane X‐ray diffraction (XRD) analysis of Langmuir–Blodgett (LB) films fabricated from both amphiphilic linear and cyclic block copolymers was performed to estimate the layer regularity at higher temperatures. Excellent heat‐resistant properties of organized molecular films created from the cyclic copolymer were confirmed. Both copolymer types showed clear diffraction peaks at room temperature, indicating the formation of highly ordered layer structures. However, the layer structures of the linear copolymers gradually disordered when heated. Conversely, the regularity of cyclic copolymer LB multilayers did not change with heating up to 50 °C. Higher‐order reflections (d₀₀₂, d₀₀₃) in the XRD patterns were also unchanged, indicative of a highly ordered structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 486–498     

Probing the early stages of solvent evaporation and relaxation in solvent‐cast polymer thin films by spectroscopic ellipsometry

The formation of solvent‐cast, poly(methyl methacrylate) (PMMA) thin films from dilute bromobenzene solutions was studied using an ellipsometry technique. Bromobenzene has a relatively high refractive index (compared to PMMA), which provides contrast in ellipsometry, allowing the concentration to be determined. The solvent also has a relatively low evaporation rate, which makes the film formation slow enough to capture via the technique. The formation of the glassy film is thus studied in situ, and information on solvent and void concentration in the thin film during the film formation process is obtained. There is evidence that nanovoids (representing intramolecular space) develop in the film when solvent evaporates. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of silicon‐based polymer films by excimer laser‐induced photo‐reaction of phenylsilane and methylphenylsilane

The synthesis of silicon‐based polymer films was studied by excimer laser (248 nm)‐induced photo‐reaction of phenylsilane and methyl‐phenylsilane at reduced pressure. IR and UV–VIS results showed that the films were composed of Si–C network structures with phenyl rings. Copyright © 2000 John Wiley & Sons, Ltd.     

Structure and tribological properties of Cu–PU–PTFE composite coatings prepared by low‐energy electron beam dispersion with glow discharge

Polytetrafluoroethylene (PTFE) composite coatings doped copper acetate and polyurethane (PU) were prepared on rubber substrate by low‐energy electron beam dispersion technique. The effects of dopant and glow discharge treatment on the surface morphology, structure and tribological properties of the coatings were investigated. The results showed that Cu–PTFE composite coatings form uniform surface and dense column structure with spherical aggregations under glow discharge treatment. PU coating shows the large size of protuberance structure but PU–PTFE coating presents spherical structure. Both of the coatings become relative dense and smooth after discharge treatment, and Cu–PU–PTFE composite coatings possess a smoother surface and lower polar component of surface energy. Cu doping weakens the crystallinity and ordering degree of composite coatings, but glow discharge increases the ordering degree and branched structure of C―H groups. Friction experiment indicated that Cu fails to improve the wear resistance of PTFE coatings but glow discharge treatment can do it. Cu–PU–PTFE coatings after discharge treatment have the higher wear resistance and lower coefficient of friction. Copyright © 2016 John Wiley & Sons, Ltd.     

The influence of casting parameters on the surface morphology of PS‐b‐P4VP honeycomb films

The “breath figures” method provides an efficient and cost‐effective method to produce highly ordered honeycomb patterns in polymeric films at micrometer and sub‐micrometer dimensions. The size and regularity of the pores can be adjusted through a series of physical and chemical parameters. In this study, amphiphilic diblock copolymers, polystyrene‐block‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) with different lengths of P4VP, were synthesized through Reversible Addition‐Fragmentation Chain Transfer polymerization. The honeycomb‐patterned films were prepared from these well‐defined polymers through the dynamic breath figures method. A series of physical parameters including solution concentration, flow rate, humidity of the flow, and the humidity of the casting environment, were delicately adjusted to systematically investigate their effects on the morphology of the films. These studies identified four key factors which were found to influence the formation of the pattern. No obvious effect was found on the pore size by changing the length of P4VP block. The result provides clear direction on the fabrication of PS‐b‐P4VP honeycomb‐patterned films and more broadly contributes a deeper understanding of the processes involved in the formation of honeycomb patterns. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3721–3732     

Preparation,characterization, and electrical properties of dual‐emissive Langmuir‐Blodgett films of some europium‐substituted polyoxometalates and a platinum polyyne polymer

A new series of organometallic/inorganic composite Langmuir‐Blodgett (LB) films consisting of a rigid‐rod polyplatinyne polymer coordinated with 2,7‐bis(buta‐1,3‐diynyl)‐9,9‐dihexylfluorene (denoted as PtP) as the π‐conjugated organometallic molecule, an europium‐substituted polyoxometalate (POM; POM = Na₉EuW₁₀O₃₆, K₁₃[Eu(SiW₁₁O₃₉)₂] and K₅[Eu(SiW₁₁O₃₉)(H₂O)₂]) as the inorganic component, and an amphiphilic behenic acid (BA) as the auxiliary film‐forming agent were prepared. Structural and photophysical characterization of these LB films were achieved by π–A isotherms, absorption and photoluminescence spectra, atomic force microscopy imaging, scanning tunneling microscopy, and low‐angle X‐ray diffraction. Our experimental results indicate that stable, well‐defined, and well‐organized Langmuir and LB films are formed in pure water and POM subphases, and the presence of Eu‐based POM in the subphase causes an area expansion. It is proposed that a lamellar layered structure exists for the PtP/BA/POM LB film in which the POM and PtP molecules can lay down with the interfacial planes. Luminescence spectra of the prepared hybrid LB films show that near‐white emission spectra can be obtained due to the dual‐emissive nature of the mixed PtP/POM blends. These Pt‐polyyne‐based LB films displayed interesting electric conductivity behavior. Among them, PtP/BA/POM 13‐layer films showed a good electrical response, with the tunneling current up to ±100 nA when the voltage was monitored between ?1 and 7 V. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 879–888, 2010     

Effects of the grain boundary on phase structure and surface morphology of TiO2 films prepared by MAO technology

Some porous titanium dioxide (TiO₂) films were prepared on flexible substrates by the method of micro‐arc oxidation (MAO) combined with magnetron sputtering (MS). The original material of MAO was Ti films prepared by MS, which was composed of columnar crystals with a diameter of less than 150 nm. The results indicated that the phase of the oxide films was mainly anatase structure, and the pore diameter of the films was about 100–300 nm. However, the phases of the oxide films prepared on Ti plates, which composed of equiaxed crystals with a diameter of 2–5 µm, were anatase and rutile structure. The pore diameter of those films was about 4–10 µm. It was suggested that the changes of the grain boundary structure of the original material could have a significant impact on the phase structure and surface morphology of the resultant TiOx films. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of novel three‐arm star azo side‐chain liquid crystalline polymer via ATRP and photoinduced surface relief gratings

A three‐arm star azo side‐chain liquid crystalline (LC) homopolymer, poly[6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate] (PMMAZO), was synthesized by atom transfer radical polymerization (ATRP) method. The polymerization of 6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate proceeded in a controlled/“living” way. A series of three‐arm star LC block copolymers (PMMAZO‐b‐PMMA) were also synthesized. The polymers were characterized by ¹H NMR, gel permeation chromatograph, and UV–vis spectra, respectively. The both polymers of PMMAZO and copolymers of PMMAZO‐b‐PMMA exhibited a smetic phase and a nematic phase. As concern to the PMMAZO, the glass‐transition temperature (T_g) and phase‐transition temperature from the smetic to nematic phase and from the nematic to isotropic phase increased with the increase of molecular weight (M_n(GPC)) of PMMAZO. The phase transition temperature of the block copolymers, PMMAZO‐b‐PMMA, with the same PMMA block was similar to that of PMMAZO. However, the T_g of the PMMAZO‐b‐PMMA decreased at low azo content and then increased with the increasing M_n(GPC) when azo content was above 61.3%. With illumination of linearly polarized Kr⁺ laser beam at modest intensities (35 mW/cm²), significant surface relief gratings formed on PMMAZO films with different molecular weights were observed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 777–789, 2008     

Cross‐Linking and Degradation Properties of Plasma Enhanced Chemical Vapor Deposited Poly(2‐hydroxyethyl methacrylate)

Plasma Enhanced Chemical Vapor Deposition (PECVD) of poly‐2‐hydroxyethyl methacrylate (pHEMA) biocompatible, biodegradable polymer films were produced alone and cross‐linked with ethylene glycol diacrylate (EGDA). Degree of cross‐linking was controlled via manipulation of the EGDA flow rate, which influenced the amount of swelling and the extent of degradation of the films in an aqueous solution over time. Noncross‐linked pHEMA films swelled 10% more than cross‐linked films after 24 h of incubation in an aqueous environment. Increasing degree of film cross‐linking decreased degradation over time. Thus, PECVD pHEMA films with variable cross‐linking properties enable tuning of gel formation and degradation properties, making these films useful in a variety of biologically significant applications.

     

A new one‐dimensional CdII coordination polymer with a two‐dimensional layered structure incorporating 2‐[(1H‐imidazol‐1‐yl)methyl]‐1H‐benzimidazole and benzene‐1,2‐dicarboxylate ligands

The N‐heterocyclic ligand 2‐[(1H‐imidazol‐1‐yl)methyl]‐1H‐benzimidazole (imb) has a rich variety of coordination modes and can lead to polymers with intriguing structures and interesting properties. In the coordination polymer catena‐poly[[cadmium(II)‐bis[μ‐benzene‐1,2‐dicarboxylato‐κ⁴O¹,O^1′:O²,O^2′]‐cadmium(II)‐bis{μ‐2‐[(1H‐imidazol‐1‐yl)methyl]‐1H‐benzimidazole}‐κ²N²:N³;κ²N³:N²] dimethylformamide disolvate], {[Cd(C₈H₄O₄)(C₁₁H₁₀N₄)]·C₃H₇NO}_n, (I), each Cd^II ion exhibits an irregular octahedral CdO₄N₂ coordination geometry and is coordinated by four O atoms from two symmetry‐related benzene‐1,2‐dicarboxylate (1,2‐bdic²⁻) ligands and two N atoms from two symmetry‐related imb ligands. Two Cd^II ions are connected by two benzene‐1,2‐dicarboxylate ligands to generate a binuclear [Cd₂(1,2‐bdic)₂] unit. The binuclear units are further connected into a one‐dimensional chain by pairs of bridging imb ligands. These one‐dimensional chains are further connected through N—H…O hydrogen bonds and π–π interactions, leading to a two‐dimensional layered structure. The dimethylformamide solvent molecules are organized in dimeric pairs via weak interactions. In addition, the title polymer exhibits good fluorescence properties in the solid state at room temperature.     

Electro‐oxidation and reduction of H2 on platinum studied by scanning electrochemical microscopy for the purpose of local detection of H2 evolution

Electrochemical detection of H₂ using scanning electrochemical microscopy (SECM) has shown to hold great promise as a sensitive characterization method with high spatial resolution for active surfaces generating H₂. Herein, the factors contributing to the current that is measured by SECM in generation/collection mode for H₂ detection are studied. In particular, the concentration gradient of H₂ at the substrate, the H₂/H⁺ recycling between the SECM tip and substrate and hemispherical profile of H₂ diffusion has been discussed. It was postulated that H₂/H⁺ recycling plays a dominant role in the oxidative current measured in generation/collection mode of SECM when the microelectrode is positioned in close vicinity of substrate. Copyright © 2015 John Wiley & Sons, Ltd.     

Coordination polymer chains built from CuII and adipate ions linked by hydrogen bonds to form a three‐dimensional framework structure

In the title compound, catena‐poly[bis[(2,2′‐bipyridine‐κ²N,N′)(1,1,3,3‐tetracyano‐2‐ethoxypropenido‐κN)copper(II)]‐μ₄‐hexanedioato‐κ⁶O¹,O^1′:O¹:O⁶,O^6′:O⁶], [Cu₂(C₉H₅N₄O)₂(C₆H₈O₄)(C₁₀H₈N₂)₂]_n, the adipate (hexanedioate) dianion lies across a centre of inversion in the space group P. The Cu^II centre adopts a distorted form of axially elongated (4+2) coordination, and the Cu^II and adipate components form a one‐dimensional coordination polymer from which the 2,2′‐bipyridine and 1,1,3,3‐tetracyano‐2‐ethoxypropenide components are pendent, and where each adipate dianion is bonded to four different Cu^II centres. The coordination polymer chains are linked into a three‐dimensional framework structure by a combination of C—H...N and C—H...O hydrogen bonds, augmented by a π–π stacking interaction.     

Changes in the surface morphology induced by 1.0‐MeV Au ion bombardment of Ti and Ti‐6Al‐4V

The effects of surface sputtering by 1.0‐MeV Au ion implantation in commercially pure Ti and its alloy Ti‐6Al‐4V have been studied. These materials are associated with applications in orthopaedic implants. There are few studies that try to explain the ion implantation process of Au in these materials when considering the effects generated on the surface by sputtering, especially at energies of the order of MeV. Discs of these materials were mirror polished and then implanted with 1.0‐MeV Au ions for 4.7 × 10¹⁷ ions/cm² at 45° incident angle with respect to the surface. Part of the eroded material was deposited simultaneously on glass slides to determine their spatial distribution. These discs and the slides were analysed by Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), optical microscopy and atomic force microscopy. The implanted materials show the initial production of surface ripples that evolve into banded structures. Copyright © 2014 John Wiley & Sons, Ltd.     

A new two‐dimensional CoII coordination polymer based on bis[4‐(2‐methyl‐1H‐imidazol‐1‐yl)phenyl] ether and biphenyl‐4,4′‐diyldicarboxylic acid: synthesis,crystal structure and photocatalytic degradation activity

A novel two‐dimensional Co^II coordination framework, namely poly[(μ₂‐biphenyl‐4,4′‐diyldicarboxylato‐κ²O⁴:O^4′){μ₂‐bis[4‐(2‐methyl‐1H‐imidazol‐1‐yl)phenyl] ether‐κ²N³:N^3′}cobalt(II)], [Co(C₁₄H₈O₄)(C₂₀H₁₈N₄O)]_n, has been prepared and characterized by IR, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. The crystal structure reveals that the compound has an achiral two‐dimensional layered structure based on opposite‐handed helical chains. In addition, it exhibits significant photocatalytic degradation activity for the degradation of methylene blue.     

The morphology and structure of PS‐b‐P4VP block copolymer films by solvent annealing: effect of the solvent parameter

Lamellae (symmetric) forming polystyrene‐b‐poly(4‐vinylpyridine) (PS‐b‐P4VP) block copolymers (BCPs) were used to produce nanostructured thin films by solvent (toluene) casting (spin‐coating) onto silicon substrates. As expected, strong micellization of PS‐P4VP in toluene results in poorly ordered hexagonally structures films. Following deposition the films were solvent annealed in various solvents and mixtures thereof. A range of both morphologies including micelle and microphase separated structures were observed. It was found that nanostructures typical of films of regular thickness (across the substrate) and demonstrating microphase separation occurred only for relatively few solvents and mixtures. The data demonstrate that simple models of solvent annealing based on swelling of the polymer promoting higher polymer chain mobility are not appropriate and more careful rationalization is required to understand these data. Analysis suggests that regular phase separated films can only be achieved when the copolymer Hildebrand solubility parameter is very similar to the value of the solvent. It is suggested that the solvent anneal method used is best considered as a liquid phase technique rather than a vapor phase method. The results show that solvent annealing methods can be a very powerful means to control structure and in some circumstances dominate other factors such as surface chemistry and surface energies. Copyright © 2009 John Wiley & Sons, Ltd.