射频等离子沉积聚硅氧烷薄膜的XPS研究

用CVD方法在一台射频放电等离子体聚合实验装置内成功地制备了沉积聚酯薄膜基底有机聚硅氧烷薄膜.该薄膜在有原子氧模拟实验装置内具有抗原子氧剥蚀的良好性能,对航天器等材料表面起到防护作用.有机聚硅氧烷薄膜与等离子体沉积时氧的泄露量有关,且沉积密度经AFM检测有较大的差异.并用XPS较详细考察了不同工艺制备的聚硅氧烷官能团构成和表面状态,以期得到优良的防剥蚀膜.     

Rheo-optical properties of polyethylene films in the nonlinear viscoelastic region

A new apparatus was designed to investigate the dynamic viscoelastic properties of solid polymer materials in the nonlinear viscoelastic region. The apparatus was combined with a birefringence apparatus in such a way that birefringence could be measured simultaneously with stress under oscillatory deformation. The nonlinear viscoelastic behavior of bulk-crystallized high-density polyethylene films was examined. Nonlinearity of mechanical properties became evident around 30°C, while optical properties became markedly nonlinear around 50°C. The nonlinearity of viscoelastic properties changes very little when the films are swollen with tetrachloroethane. It is proposed that disruption of lamellae to crystallites in the drawing process is one of the most important causes of the nonlinear behavior of high-density polyethylene films.     

二氧化钛/聚乙烯吡咯烷酮纳米复合薄膜的制备与表征

采用溶胶-凝胶法(so1 gel)制备了TiO2/聚乙烯吡咯烷酮(PVP)有机 无机纳米复合薄膜.采用扫描电子显微镜、接触角测定仪、红外光谱仪、紫外 可见吸收光谱仪和静 动摩擦系数测定仪对所制备的TiO2/PVP纳米复合薄膜进行了结构表征和性能研究.结果表明:所制备的TiO2/PVP纳米复合薄膜表面平整光滑、无裂纹、具有一定的疏水性、良好的透明性、防紫外线性能和减摩抗磨性能.     

A novel apparatus combining polymer extrusion processing and x-ray scattering

A novel apparatus was designed and constructed combining polymer extrusion processing and x-ray scattering. It allows direct, real time monitoring of structure and temperature development in polymer material during extrusion. The apparatus involves a vertical industrial extruder equipped with a four-roll stretching device to mimic the processing environments of uni-axially oriented films or sheets, a simultaneous small and wide angle x-ray scattering system and an infrared thermometer as detection unit. The charging barrel of the extruder and the stretching device can be moved upward and downward precisely. By moving the sample along the center line, structure and temperature development as a function of position can be obtained. The performance of the apparatus was verified by a test experiment, which allows us to establish the relationship between processing parameters and evolution of structure with different length scales, and may lead to a better understanding of the physics in polymer processing.     

Dynamic strain-birefringence apparatus for polymer films

A new apparatus for investigating dynamic strain birefringence in polymer films at frequencies up to 10 Hz and at various degrees of internal sample orientation is described. Samples are elongated at constant low rates while simultaneously being strained sinusoidally. Fast changes in sample retardance are recorded while slow changes are automatically compensated with a servo-controlled Soleil-Babinet compensator. The signal-to-noise ratio of the system is greatly enhanced by incorporating a highly monochromatic laser light source, a synchronous amplifier, and a light beam modulator based on a rotating polarizer. Data obtained from this apparatus can be used to elucidate polymer relaxation mechanisms at various frequencies over a wide range of static strains.     

等离子体聚合膜的电学性质研究：Ⅰ.TCNQ聚合膜的结构和电学性质

本文采用内部电极、电容耦合式钟罩型射频等离子体聚合装置,首次进行了四氰代对二次甲基苯醌(TCNQ)的等离子体聚合,得到了电导率为10~(-8)～10~(-6)Scm~(-1)的聚合物半导体薄膜。由这些聚合物薄膜制备的Al/聚合膜/ITO(铟锡氧化物透明电极)夹层元件显示出整流特性和光生伏打效应。这种聚合物薄膜还具有光电导性质。红外光谱(IR)、紫外光谱(UV)的研究结果表明,优良的半导体特性归因于聚合膜中存在有较大范围的π电子共轭结构。     

Application of TG for valuation of selected aliphatic diamide stabilisation effect on low density polyethylene

Spontaneous structural changes of a polymer that is its ageing due to thermal energy, radiation energy, chemical compounds and micro-organisms lasting at least several season cycles change the characteristics of polymer products. Changes of polymer characteristics found during ageing can be reversible or irreversible. The most substantial changes occur as the result of UV radiation. Tests of selected aliphatic diamides of terephthalic acid as stabilisers of low density polyethylene (LD-PE) used for the production of gardening films were performed. Accelerated ageing of films for a period of one year was done in the Xenotest Alpha type apparatus. Studies were made for 0.1 mm thick commercial films. Studies of selected mechanical properties of LD-PE films without stabilisers and of LD-PE sheeting containing an addition of one of the synthesised diamides of terephthalic acid or the standard Tinuvin 783 stabiliser were performed before and after the ageing process. To determine the effect of stabilisers on the ageing process of LD-PE films, thermogravimetric analysis was applied. This allowed us to determine the decomposition activation energy of the investigated films before and after the ageing process and the influence of stabilisers on the observed changes. This revised version was published online in July 2006 with corrections to the Cover Date.     

GRAFT COPOLYMERIZATION OF ACRYLAMIDE ONTO POLYPROPYLENE FILMS BY PLASMA TECHNIQUE

The graft copolymerization of acrylamide onto polypropylene (PP) Film was carried out by using a capacitively coupled rf plasma apparatus with external plate electrodes. The relationship between the surface structure of the Ar plasma-treated PP films and the extent of grafting of acrylamide on the films was studied through observing the effects of discharge power and exposure time on the relative content of free-radical on the film surface. Meanwhile, the wettability and surface energy of the PP film were measured.     

Effect of β-sheet crystalline content on mass transfer in silk films

The material properties of silk are favorable for drug delivery due to the ability to control material structure and morphology under ambient, aqueous processing conditions. Mass transport of compounds with varying physical-chemical characteristics was studied in silk fibroin films with control of β-sheet crystalline content. Two compounds, vitamin B12 and fluorescein isothiocynate (FITC) labeled lysozyme were studied in a diffusion apparatus to determine transport through silk films. The films exhibited size exclusion phenomenon with permeability coefficients with contrasting trends with increases in β-sheet crystallinity. The size exclusion phenomenon observed with the two model compounds was characterized by contrasting trends in permeability coefficients of the films as a function of β-sheet crystallinity. The diffusivity of the compounds was examined in the context of free volume theory. Apart from the β-sheet crystallinity, size of the compound and its interactions with silk influenced mass transfer. Diffusivity of vitamin B12 was modeled to define a power law relationship with β-sheet crystallinity. The results of the study demonstrate that diffusion of therapeutic agents though silk fibroin films can be directed to match a desired rate by modulating secondary structure of the silk proteins.     

Oxidative and tribological properties of amorphous and quasicrystalline approximant Al-Cu-Fe thin films

The origins of the tribological properties and corrosion resistance of amorphous and quasicrystalline approximant alloys have been studied by comparing their properties in thin Al-Cu-Fe alloy films with compositions lying near the quasicrystalline region of the ternary compositional phase diagram. Six sputtered thin films of an Al-Cu-Fe alloy were studied using X-ray diffraction, X-ray photoemission spectroscopy (XPS), and an in situ ultrahigh vacuum (UHV) tribometer. The films were annealed in UHV to induce the formation of orthorhombic, rhombohedral, and amorphous bulk structures. The properties of these thin films were then determined in the same UHV apparatus without exposing the films to air. The rates of surface oxidation by H2O and O2 were measured using XPS. Although the oxidation rates and oxide thicknesses were dependent on the oxidant, they were not sensitive to the structures of the films. Friction was measured between identical samples in sliding contact. The friction coefficients (micros = 0.36 +/- 0.11 to 0.56 +/- 0.08) were comparable to those observed in other experiments using quasicrystals and approximants in UHV; however, there was no strong correlation between the friction coefficients and either the film structure or the degree of surface oxidation. These results suggest that the tribological and corrosion resistance properties of these quasicrystalline approximant alloys are not directly connected to crystalline structure.     

Measurement of odour permeability of polypropylene packaging films at low odourant levels

An apparatus has been designed to measure the permeability coefficients of packaging films to odours at low odour concentration gradients. Use of the apparatus is illustrated by comparison between the permeation behaviour of coextruded and coated polypropylene packaging films, using the test odourants benzyl acetate, 2-methoxyphenol and limonene. For the coextruded films, permeability coefficients decrease logarithmically with concentration at odour levels in the parts per million range. The coated films exhibit more complex behaviour; at low concentrations extremely long induction periods occur prior to odourant detection, whilst at higher odourant levels the barrier coatings become less effective and the permeability coefficients approach those of coextruded film.     

Mixed thin films of a cationic amphiphilic porphyrin and n-alkanes

Langmuir and Langmuir-Blodgett (LB) films of a cationic amphiphilic porphyrin mixed with n-alkanes octadecane and hexatriacontane were prepared and characterized, to examine the influence of the alkanes on film structure and stability. While the structure present in these films was controlled primarily by the porphyrin, the addition of the alkanes resulted in significant changes to both the phase behavior of the Langmuir films and the molecular arrangement of the LB films. These changes, as well as the observed chain length effects, are explained in terms of the intermolecular interactions present in the films.     

The use of heat flow apparatus to find polymer transition points

As changes that occur at transition points, e.g. the glass temperature of polymers, involve factors such as thermal conductivity rather than exothermic or endothermic reactions it was considered that heat flow would be the most suitable technique to study the occurrence of these transitions. A simple heat flow apparatus is described and examples are given of its application to polymer films and to co-polymers.     

On the deformation mechanisms of oriented PET and PP films under load

Uniaxially orienred semicrystalline poly(ethylene terephthalate) (PET) and poly(propylene) (PP) films were loaded parallel to draw direction at various temperatures. Changes in the submicroscopical structure of the films under load were examined by small and wide-angle x-ray scattering (SAXS; WAXS) and birefringence measurements. WAXS measurements reveal a decrease of the initial high orientation of the chains in the crystallites during deformation. Simultaneously, an increase of the birefringence was detected, indicating an orientation of chains in the amorphous regions. The alteration of the long period reflections in the SAXS patterns give strong evidence that lamellar stacks with different orientation angles according to load direction are present. Depending on the orientation of stacks, the contribution of lamellar separation to sample deformation alters, giving rise to different amounts of density changes in the stacks. Absolute intensity measurements of SAXS using a Kratky apparatus reveal that lamellar separation occurs preferentially below or in the range of the glass-transition temperature at small strain. With increasing strain and temperatures above the glass-transition slip deformation mechanisms become more important. The formation of microvoids was observed at strain near to elongation at break below or in the range of glass-transition temperature.     

Multilayer nitroazobenzene films covalently attached to carbon. An AFM and electrochemical study

Nitroazobenzene films have been grafted to pyrolyzed photoresist films by electrochemical reduction of the corresponding diazonium salt in acetonitrile solution. Two component films were also prepared by electrochemically grafting methylbenzene layers to preformed NAB films. Voltammetric investigation of the films in aqueous acid medium and the measurement of film thickness using atomic force microscopy (AFM) lead to new insights into film structure. In aqueous acid solution, the azobenzene groups have no detectable electroactivity and not all nitro groups in the films can be reduced. These findings point to a compact film structure in which proton diffusion is limited. There may also be spatial inhibition of the conformational changes that accompany azobenzene reduction. For increasingly thick NAB films, the peak for reduction of the nitro groups moves to more negative potentials and the peaks become more asymmetric in shape. These changes are interpreted in terms of the dielectric properties and the rate of proton diffusion in the films. Film thickness was measured by ploughing through the film with an AFM tip. When an NAB film prepared in acetonitrile solution is reduced in aqueous acid, the film thickness decreases by more than 50%. The changes can be partially reversed by treatment in acetonitrile-electrolyte solution and hence are attributed to ion-solvent induced swelling and shrinking. Thus, the large decrease in thickness detected by AFM after treatment of the film in aqueous acid is consistent with the compact film structure revealed by electrochemistry.     

Ageing and fatigue of lead titanate and lead zirconate titanate thin ferroelectric films

The phenomena of ageing and fatigue have been experimentally investigated in lead titanate and lead zirconate titanate thin ferroelectric films for samples on different substrates and with different materials of the measuring electrodes. A certain broadening of the dielectric permittivity peak is observed for the films on the silicon substrate after a year keeping without external actions. The lead titanate films on corundum substrates did not demonstrate visible changes in structural and dielectric parameters in the course of this time. In the course of repeated cycling the reduction of switching polarization in the lead titanate and lead zirconate titanate films on silicon substrates takes place at considerably greater number of cycles as compared to the same films on corundum substrates under the identical conditions. The above changes of dielectric and switching characteristics can be relevant to the changes in the domain structure of the materials under investigation in the process of their ageing and repeated switching. The reason for the acceleration of the ageing processes in the films on corundum substrates could be either an increase in the absolute magnitude of the switching field or an increase of the internal bias field, that facilitate the migration of oxygen vacancies in the films with the perovskite structure to the electrode–ferroelectric surface with the consequent fixation of domain walls.     

Ramp rate effect on polyimide film properties and morphology

The stress in films of semirigid and rigid polyimides (PIs) on silicon (Si) substrate has been measured in situ during curing using a newly modified bending beam apparatus. By using the apparatus, the onset of residual stress in the initially solvent-rich films has also been investigated. The stress characteristics of the PI films are strongly ramp rate dependent. Different ramp rates result in markedly different stress patterns, thermo-mechanical properties, and film morphologies. The residual stress at room temperature after curing is scattered around 23–31 MPa for the films of pyromellitic dianhydride-4,4′-oxydianiline (PMDA-ODA). For pyromellitic dianhydride-p-phenylenediamine (PMDA-PDA), it systematically increases from ?6 to 28 MPa for ramp rate increasing from 0.5 to 10°C/min. The residual stress is very low in the slowly cured PMDA-PDA films. However, these films have gone through a very high-stress transient state during curing. The maximum transient stress is comparatively higher in the films of PMDA-PDA than in PMDA-ODA. Slowly cured PMDA-PDA films exhibit high structural ordering, high in-plane anisotropy, and low coefficient of thermal expansion. ©1995 John Wiley & Sons, Inc.     

Photoemission studies of polythiophene and polyphenyl films produced via surface polymerization by ion-assisted deposition

Conducting polymer films are grown by mass-selected, hyperthermal thiophene ions coincident on a surface with a thermal beam of organic monomers of either alpha-terthiophene (3T) or p-terphenyl (3P) neutrals. Mass spectrometry and X-ray photoelectron spectroscopy previously verified polymerization of both 3T and 3P by 200 eV C(4)H(4)S(+) during surface polymerization by ion-assisted deposition (SPIAD). The electronic structure of these films are probed here by ultraviolet photoelectron spectroscopy (UPS) and polarized near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and compared with similar spectra of evaporated films. The conducting polymer films formed by SPIAD display new valence band features resulting from a reduction in both their band gap and barrier to hole injection, which are calculated from the occupied and unoccupied valence band states measured by UPS and NEXAFS. These changes in film electronic structure result from an increase in the electron conjugation length and other changes in film structure induced by SPIAD.     

Dynamic examinations at photoresists by reflectance spectroscopy

Summary An optical device is introduced, which allows the observation of the changes of chemical and physical properties of photoresists during irradiation. The photoresists are fixed as thin films at the surface of either semiconductor elements or circuit boards. The apparatus allows on-line process control during the photochemical reactions taking place in photoresists. By use of fiber optics and a photodiode array the spectral reflectance can be measured repetitively within 15 ms. This fast repetition rate allows on-line process control even during short radiation times, which are usual in practice to produce a pattern in the photoresists for the micro structuring of circuit boards or semiconductor wafers. The possibilities of the method and details of the apparatus are demonstrated at given examples of photoresists.

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Dynamische Untersuchungen an Photoresisten über Reflexionsspektroskopie

     

Molecular modeling of adsorption and ordering at solid interfaces

Interfaces between liquids and solid surfaces are of considerable scientific as well as technological interest, in particular in the context of the adsorption and organization of molecular films. In recent years the direct observation of the molecular structure and often even the dynamics of ordered monolayers at such hidden interfaces has been made possible by the rapid development in scanning probe microscopy. Nevertheless, there is still a lack of understanding with respect to the formation and organization of such films and their interaction with the experimental apparatus. Here computer modeling plays an increasing role as both the complexity of the interfaces and the available computer power increase. This article addresses the application of phenomenological molecular modeling to physisorption at solid surfaces with a special emphasis on the liquid-solid interface. The paper presents an overview over different modeling approaches and illustrates their application in a series of examples ranging from the simulation of adsorption isotherms of small molecules to the prediction of the structure of physisorbed layers for larger molecules.