Si nanopillar arrays with nanocrystals produced by template-induced growth at room temperature

Well-aligned and closely-packed silicon nanopillar (SNP) arrays are fabricated by using a simple method with magnetron sputtering of Si on a porous anodic alumina (PAA) template at room temperature. The SNPs are formed by selective growth on the top of the PAA pore walls. The growth mechanism analysis indicates that the structure of the SNPs can be modulated by the pore spacing of the PAA and the sputtering process and is independent of the wall width of the PAA. Moreover, nanocrystals are identified by using transmission electron microscopy in the as-deposited SNP samples, which are related to the heat isolation structure of the SNPs. The Raman focus depth profile reveals a high crystallization ratio on the surface.     

pH‐Sensitive Polyacrylic Acid (PAA) Hydrogels Trapped with Polysodium‐p‐Styrenesulfonate (PSS)

The preparation of a new type of semi‐interpenetration network system of polyacrylic acid (PAA) hydrogel trapped with polysodium‐p‐styrenesulfonate (PSS) is presented. The structure and response properties of PAA/PSS were investigated by Fourier transform infrared (FTIR) analysis and pH and ionic intensity stimuli‐responsive measurement. The FTIR analysis proved the successful intermingling of PSS into PAA. The swelling behavior of PAA hydrogel in an alkaline environment was improved due to the addition of PSS. As the ionic concentration in solution increased, the swelling rate of PAA decreased after adding PSS. However, the swelling velocity of the pure PAA is quicker than that of the PAA/PSS samples since the PSS will enhance the entanglement of this hydrogel network and slow down the swelling velocity. Multi‐interactions between the PAA hydrogel network and trapped PSS chains, including electrostatic repulsive interaction, entanglement interaction, ionic intensity interaction, and osmotic pressure, were proposed to explain the earlier‐mentioned experimental phenomena.     

Interfacial morphology and friction properties of thin PEO and PEO/PAA blend films

The scanning force microscope (SFM) was used to investigate morphology of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blend. The effect of solvent and dewetting in surface structure of PEO film was reported. The results manifested that the crystallization of PEO could be suppressed completely in ultrathin region via using chloroform as a solvent, and the branched-like crystallization was recovered after dewetting. Also, the effect of thickness, the ratio of PEO/PAA and dewetting in surface morphology of PEO-PAA blend films were investigated. These results showed that the crystallization was highly dependent on the ratio of PEO/PAA and the thickness of blend film. Furthermore, we assembled the PEO/PAA layer-by-layer film by spin-casting method for the first time, which exhibited highly efficiency. As a complementary tool, we also used lateral force microscopy (LFM) to explore surface information of these films. The result was indicative of interfacial constraints in ultrathin region, and also was supported by the results showing the spin-casting PEO/PAA blends rather than heterogeneous mixture.     

Near edge X-ray absorption fine structure (NEXAFS) of model compounds for the humic acid/actinide ion interaction

To understand spectral features of humic acid (HA) C 1s-near edge X-ray absorption fine structure (NEXAFS) with and without metal ion complexation, a set of model compounds is investigated. Halogenated benzoic acids and anthranilic acid are examined to demonstrate the effect of electron withdrawing groups on the C 1s-NEXAFS spectra of complex organic acids, including HA. The peak positions for aromatic and carboxylic groups in these spectra are in agreement with common assignments. The spectral position of the peak for substituted aromatic carbon shifts with increasing electronegativity of the substituent to higher photon energies. Polyacrylic acid (PAA) and different PAA metal ion complexes are investigated as model substances for metal cation complexation by HA. Tb(III)-, Zr(IV)- and U(VI)–PAA exhibit general spectral signatures previously observed for the PAA/Eu(III)–PAA system. For these different metal cations, similar spectral changes and distinct variations in peak intensities are observed going from the uncomplexed to the metal-loaded macromolecules. These spectral changes are comparable to those for U(VI)- and Th(IV)–HA systems.     

含分枝铜纳米线多孔铝膜的偏振特性

利用二次阳极氧化法制备了具有分枝结构的多孔铝(PAA)模板,并以交流电化学沉积的方法在该模板中合成了分枝状的铜纳米线。用SEM观察样品的形貌结构,用分光光度计测量了样品的透射光谱和偏振光谱。实验结果表明,含分枝状铜纳米线结构的多孔铝膜在近红外光区具有较高的透射率,且得到了14～22 dB的消光比。这种微偏振器件制备方法简单、效率高、造价低,在光电集成领域有着广泛的应用前景。     

制备条件对含铜阳极氧化铝复合薄膜偏振特性的影响

利用多孔阳极氧化铝(PAA)的纳米列阵结构,将金属铜电镀到氧化铝的孔中,得到含有金属铜纳米列阵阳极氧化铝(Cu/PAA)膜。实验中发现,Cu/PAA膜的偏振特性与电镀条件有关。在一定的范围内,随着电镀时间和电流密度的增加,消光比增大。电镀溶液的温度也是影响Cu/PAA膜消光比的一个很重要的因素,在电镀溶液温度相对较高的情况下,电流密度相对较小时也可以获得相对较高的消光比。通过优化电镀条件可获得高效率的Cu/PAA膜微偏振器。这种电化学方法制备的微偏振器,制备工艺简单,尺寸可控,便于实现产业化,有广泛的应用前景。     

Deposition of polyimide precursor by resonant infrared laser ablation

We report the successful deposition of a polyimide precursor using resonant infrared laser ablation (RIR-LA). A solution of poly(amic acid) (PAA) dissolved in N-methyl-2-pyrrolidinone (NMP), the melt processable precursor to polyimide, was frozen in liquid nitrogen for use as an ablation target in a high-vacuum chamber. Fourier transform infrared spectroscopy was used to determine that the local chemical structure remained unaltered. Gel permeation chromatography demonstrated that the transferred PAA retained its molecular weight, showing that RIR-LA is able to transfer the polymer intact, with no detectable chain fragmentation. These results are in stark contrast to UV-processing which degrades the polymer. After deposition the PAA may be removed with a suitable solvent; however, once the material has undergone cyclodehydration it forms an impenetrable three-dimensional network associated with thermosetting polymers. The transfer of uncured PAA precursor supports the hypothesis that RIR-LA is intrinsically a low temperature process, because the PAA is transferred without reaching the curing temperature. The RIR-LA also effectively removes the solvent NMP from the PAA, during both the ablation and deposition phases; this is a necessary step in generating PI films. PACS 41.60.Cr; 78.30.Jw; 81.15.Fg     

Cure Behavior and Thermal Properties of Poly (Amide-Amidic Acid) Modified Diglycidyl Ether of Bisphenol-A/4,4′-Diaminodiphenylsulfone

Poly (amide-amidic acid) (PAA) was selected to modify diglycidyl ether of bisphenol-A (DGEBA)/4,4′-diaminodiphenylsulfone (DDS). The cure behavior was studied by means of nonisothermal differential scanning calorimeter (DSC) analysis, indicating that PAA played a role of catalyst during the process of the curing reaction. Results of Fourier transform infrared spectroscopy (FT-IR) analysis showed that the PAA acted as a co-curing agent when the PAA content was 3.2–38.4 phr and also as a modifier when the PAA content was 12.8–38.4 phr. The glass transition temperature (T_g ) decreased with the increase of PAA content. The thermal stability improved when the PAA content was 3.2–6.4 phr because of the catalytic effect of PAA. The flexural strength improved for the varying PAA content studied in this work, with the highest flexural strength being obtained when the PAA content was 6.4 phr. The fracture surface morphology was observed using scanning electron microscopy (SEM); the morphologies varied with changing content of PAA.     

基于包络线法的多孔阳极氧化铝薄膜光学常数的计算

采用二步阳极氧化法在草酸溶液中制备了多孔阳极氧化铝(PAA)薄膜。借助于扫描电子显微镜(SEM)分析了多孔阳极氧化铝薄膜的微观形貌。结果发现,在其表面孔径为30~40nm的六边形孔洞分布均匀,且垂直于表面平行生长。依据PAA透射光谱的实验数据,采用极值包络线算法计算出了PAA薄膜的复折射率以及光学能隙等光学常数。通过分析吸收系数与入射光子能量之间的关系发现,PAA薄膜具有直接带隙半导体的电子结构特征,而且由理论计算得到的PAA的带隙能与其光致发光谱的峰位能是一致的。     

Polarization properties of porous anodic alumina with Y-branched Cu nanowires

Porous anodic alumina (PAA) templates with branch structure are fabricated by the two-step anodic oxidation processes, and then the Y-branched Cu nanowires are synthesized in the templates using an alternating current (AC) deposition method. We observe the morphology image of the samples by scanning electron microscopy (SEM), and measure the transmission spectrum and the polarization spectrum of the samples by the spectrophotometer. The results show that PAA films with Y-branched Cu nanowires have better transmittance in the near infrared region. An extinction ratio of 15-18 dB and an insertion loss of 0.1-0.4 dB are obtained in this region. Therefore PAA with Y-branched Cu nanowires can be used as a near-infrared micropolarizer, and this kind of micropolarizer would have a promising future in the field of photoelectricity integration.     

Effect of Polyacrylic Acid on Phase State of Lipids and Diffusion in Lipid-Water System

Lipid vesicles interacting with polyanions are promising for controlled drug delivery. However, different aspects of the interaction of these polymers with lipids are far from complete understanding. In this work we studied the influence of polyacrylic acid (PAA) with small concentrations (1–4 mol%) on the change of the phase state, lateral diffusion of these lipids in lamellar phase and transmembrane water diffusion in macroscopically oriented bilayers of lipid-water systems formed by dimiristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine. Measurements were performed by ³¹P nuclear magnetic resonance (NMR) spectroscopy and the ¹H NMR technique with a pulsed field gradient. It was found that the presence of PAA does not change the lamellar structure of the system. However, a part of bilayers changes their originally flat geometry and forms vesicles with a higher surface curvature. Macroscopic orientation of bilayers disappeared. For DMPC the presence of PAA leads to a shift of the gel-to-liquid crystalline phase-transition temperature to higher temperatures. An increase of PAA concentration leads to a monotonous decrease in the lateral diffusion coefficient of lipids that is caused, probably, by the ordering of lipids in bilayers. The transbilayer diffusion coefficient of water increases in the presence of PAA, but it depends slightly on the PAA concentration. An increase of pH leads to a change of the lipid lateral and transbilayer diffusion coefficients to the values typical for a pure bilayer. Authors' address: Andrey Filippov, Kazan State University, Kremlevskaya ulitsa 18, Kazan 420008, Russian Federation     

Bioactivity and cytocompatibility of dicalcium phosphate/poly (amino acid) biocomposite with degradability

A bioactive composite of dicalcium phosphate (DCP) and poly (amino acid) (PAA) was fabricated, and the in vitro bioactivity, degradability, and cellular responses to the DCP/PAA composite (DPC) were investigated as compared to PAA. Apatite formation on DPC surfaces occurred after immersion into simulated body fluid (SBF) for 7 days, but not on the surface of PAA. The weight loss ratio of DPC could reach 18.6 ± 0.3 wt% after soaking into phosphate buffered saline (PBS) for 2 months, which was higher than PAA (11.0 ± 0.2 wt%). Cell attachment and proliferation of MG-63 cells on DPC was obviously higher than on PAA. Moreover, the cells spread and formed confluent layer on the DPC surfaces. The alkaline phosphatase activity (ALP) of the cells on DPC was significantly greater than PAA at day 5 and day 7. The results suggested that introducing DCP into PAA makes the composite bioactive and more degradable, and meanwhile enhances osteoblast-like cells attach, proliferation and osteogenic differentiation.     

Mechanical Strength and Tribological Properties of Diglycidyl Ether of Bisphenol-A Cured by Poly(Amide-Amidic Acid) and 4,4’-Diaminodiphenylsulfone

Diglycidyl ether of bisphenol-A (DGEBA) was cured by poly(amide-amidic acid) (PAA) and a commonly used curing agent, 4,4’-diaminodiphenylsulfone (DDS), in different molar ratios. It was found that the flexural strength, tensile strength, tribological properties, and thermal stability strongly depended on the molar ratios of PAA and DDS in the mixed curing agents. The highest flexural strength was obtained when DGEBA was cured with PAA individually. The tensile strength increased with the increase of PAA content in the mixed curing agents. The DGEBA cured with PAA containing curing agents possessed lower friction coefficient than that cured with DDS individually. The wear rate greatly decreased with the PAA content increasing in the mixed curing agent. Tribological behaviors and wear mechanisms were discussed by observing the morphology of wear debris and worn surfaces of the tested samples using scanning electron microscopy (SEM).     

Energy transfer in porous anodic alumina/rhodamine 110 nanocomposites

We have used porous anodic alumina (PAA) films as templates for embedding rhodamine 110 (Rh110) molecules and examined their photoluminescence (PL) properties in detail. The analysis of the polarization memory (PM) of PL strongly suggests that there is a significant energy transfer from PAA to Rh110 molecules. The effect of annealing the PAA layer on the PL properties of the nanocomposite has been studied. The results show that the energy transfer becomes more efficient in annealed PAA.     

Effect of Cationic Polyelectrolyte on the Flow Behavior of Hydroxypropyl Methyl Cellulose/Polyacrylic Acid Interpolymer Complexes

Association of polyacrylic acids and nonionic polymers in solutions via hydrogen bonding results in formation of novel polymeric materials. These complexes are novel individual compounds and their properties are entirely different from the properties of their component polymers. In this study, the effects of a cationic polyelectrolyte (polyethylenimine, PEI) on the interpolymer complexation of hydroxypropyl methyl cellulose (HPMC) with polyarcylic acid (PAA) in aqueous media were studied. Results showed that at low pH, interpolymer complex (IPC) formation was observed between HPMC and PAA at a 3:0.5 polymer ratio. Under basic conditions, the viscosity of the IPC increased accompanied with the transition from coiled structure to an extended conformation of associates. Addition of PEI to the same system caused some structural changes in the polymer solution mixtures depending on the pH of the system. PEI worked as a destructive agent for the HPMC/PAA interpolymer complexes and associates. This behavior was attributed to the complex formation between PEI and HPMC via hydrogen bonding.     

聚丙烯酸水溶液及α-A12O3悬浮液的流变性研究

研究了pH、聚丙烯酸（PAA）浓度和分子量对PAA水溶液的粘度的影响,发现溶液的流变行为与溶液中PAA高分子链的离子化程度和构型密切相关,高分子链刚性程度的增加和链的伸展使溶液在pH为7－9时的粘度最大;研究了在PAA溶液中引入陶瓷粉体后悬浮液的粘度变化,发现当陶瓷粉体和PAA的量达到一定比值时悬浮液体系的粘度达到最小值,同时发现陶瓷粉体的粒径大小与这一粘度最小值和悬浮液流变特性也有关。     

Curing Behavior and Mechanism of Diglycidyl Ether of Bisphenol-A in the Presence of Poly (Amide–Amidic Acid) and 4,4′-Diaminodiphenylsulfone

Poly (amide-amidic acid) (PAA) and 4, 4′-diaminodiphenylsulfone (DDS) with varying molar ratios were used as co-curing agents to cure diglycidyl ether of bisphenol-A (DGEBA). The curing process was investigated. The differences between PAA and the conventional curing agents are discussed relative to the curing behavior and mechanism when cured with DGEBA. It was found that a lower temperature was needed to cure DGEBA when PAA was used as co-curing agent with DDS. There was only one step during the curing process of DGEBA and PAA, compared with the conventional curing agents (two steps). The activation energy (E) of the curing process of DGEBA with the co-curing agents, computed using model free estimations, was lower than that with DDS and PAA individually.     

The effect of interphase modification on carbon fiber/polyarylacetylene resin composites

Interfacial modification for carbon fiber (CF) reinforced polyarylacetylene (PAA) resin, a kind of non-polar, was investigated. The high carbon phenolic resin was used as coating to treat the surface of CF after oxidation. Atomic force microscopy (AFM) with force modulation mode was used to analyze the interphase of composite. The interlaminar shear strength (ILSS) and mechanical properties of CF/PAA composites were also measured. It was found that the CF/PAA composites treated with oxidation and coating after oxidation had transition area between carbon fiber and PAA resin. The existence of transition area led to the improvement of interfacial performance of composites. Specially, the thickness and stiffness of interphase of composite treated with coating after oxidation were more suitable for CF/PAA composites. Thus, the composite treated with coating after oxidation had the highest value of ILSS and the best mechanical properties.     

Investigation of the super-long alumina nanowire array synthesized with a novel method

Alumina nanowire array standing on porous anodic alumina (PAA) membrane has been directly and efficiently synthesized in oxalic acid solution by one-step electrochemical anodic oxidation with changing anodic voltages. The morphology of the nanowires on PAA was observed by scanning electron microscopy (SEM). The different patterns on the surface of the sample were synthesized due to the reaction time. The fine structure of the patterns has shown that the pattern is composed of the alumina nanowire array and the morphologies of the patterns can mainly be attributed to the differences in the length of the alumina nanowires. The method of selected area electron diffraction (SAED) for transmission electron microscopy (TEM) has shown that these nanowires are amorphous. An etching model was given to explain the formation mechanism of the amorphous alumina nanowires.     

Calculations of neutron diffraction patterns obtained with a nematic liquid crystal

Recently, neutron diffraction data obtained with a fully deuterated sample of the nematic liquid crystal para-azoxyanisole (PAA) were reported. In the present paper a number of simple ideas which contribute to an understanding of these data are presented. It is shown that part of the structure of the observed diffraction patterns can be attributed to the wavelength dependence of a molecular form-factor. Further, it is found that diffuse scattering observed in PAA just below its melting point may be explained in terms of oscillations of molecules about their long axes. The temperature dependence of this diffuse scattering suggests that the melting of PAA may be driven by a soft torsional mode or modes. The explanation of the diffuse scattering from the solid and the similarities between the diffraction patterns of solid and nematic phases suggest that scattering from the nematic phase might be explicable in terms of hindered rotations of molecules about their long axes. A simple model based on this hypothesis and on the neglect of short-range orientational correlations of the molecular long axes is proposed. A comparison of results obtained from this model with the experimental data demonstrates that there is considerable short-range ordering of the long molecular axes in both the nematic and isotropic-liquid phases of PAA.