Analytical investigations of poly(acrylic acid) coatings electrodeposited on titanium-based implants: a versatile approach to biocompatibility enhancement

A polyacrylic acid film was synthesized on titanium substrates from aqueous solutions via an electroreductive process for the first time. This work was done in order to develop a versatile coating for titanium-based orthopaedic implants that acts as both an effective bioactive surface and an effective anti-corrosion barrier. The chemical structure of the PAA coating was investigated by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was employed to evaluate the effect of annealing treatment on the morphology of the coatings in terms of their uniformity and porosity. Inductively coupled plasma mass spectrometry was used to measure ion concentrations in ion release tests performed on Ti-6Al-4V sheets modified with PAA coatings (annealed and unannealed). Results indicate that the annealing process produces coatings that possess considerable anti-corrosion performance. Moreover, the availability and the reactivity of the surface carboxylic groups were exploited in order to graft biological molecules onto the PAA-modified titanium implants. The feasibility of the grafting reaction was tested using a single aminoacid residue. A fluorinated aminoacid was selected, and the grafting reaction was monitored both by XPS, using fluorine as a marker element, and via quartz crystal microbalance (QCM) measurements. The success of the grafting reaction opens the door to the synthesis of a wide variety of PAA-based coatings that are functionalized with selected bioactive molecules and promote positive reactions with the biological system interfacing the implant while considerably reducing ion release into surrounding tissues. Figure Vanadium release from bare Ti-6Al-4V sheets compared with the release from sheets coated with annealed and unannealed electrosynthesised PAA Dedicated to Professor P.G. Zambonin on the occasion of his 72nd birthday.     

一种新的光致变色膜：Na2WO4-PAA-Glycerol体系研究

A method for preparing Na₂WO₄-PAA-Glycerol photochromic films was reported. The film was composed of Na₂WO₄, PAA and Glycerol, which were coated on a glass substrate. The film turned blue in the sun, and bleached to transparent in the darkness. The UV-Visible spectra showed strong absorbance at 300～500 nm, and the ABS changed signifanctly at 500～800 nm. The film showed the best photochromic behavior when n_Na2WO4∶n_PAA is 4%～5%. The mechanism was suggested that after irradiation, poly tunstate produced by Na₂WO₄ and PAA formed the tungsten blues. The tungsten blues were bleached due to oxidation back to poly tunstate by oxygen. The film showed not only an excellent photochromism property with rapid response and good reversibility, but also the simple techniques and good stability.     

一种加成固化型热固性树脂PN-PAA固化过程和热稳定性研究

研究了炔丙基醚化酚醛树脂(PN)与聚芳基乙炔树脂(PAA)的反应性共混物(以下简称PN-PAA共混树脂)的相容性,并对共混树脂的固化过程和固化物的耐热性进行了表征.相态、DSC、SEM、TEM等测试结果均表明共混树脂及其固化物是完全相容的均相体系.凝胶时间、粘度、DSC等结果表明共混树脂固化工艺性优良,适合多种成型工艺(如RTM),显著改善了PAA树脂的固化工艺缺陷.DMA、TGA等分析表明共混树脂固化物具有很高的耐热性,可作为新型的防热复合材料和高温结构材料的基体.     

磁性碳纳米管吸附去除水中甲基橙的研究

采用高温催化裂解法制备碳纳米管,对其用浓硝酸氧化法进行纯化处理,并用化学共沉淀方法制备了磁性碳纳米管(简称磁性管)。利用场发射扫描电子显微镜对磁性管进行了表征。将磁分离技术应用于碳纳米管吸附性能研究,探索碳纳米管负载磁性颗粒后对甲基橙的吸附性能,寻找最佳实验条件,对吸附质溶液进行紫外-可见吸收光谱分析。同时,进行了磁性管的脱附和再吸附性能研究。     

等离子接枝处理的CF/PAA复合材料层间剪切强度及其形貌研究

采用等离子技术对碳纤维(CF)进行接枝芳基乙炔(PAA)处理,研究了影响CF／PAA复合材料层间剪切强度(ILSS)的因素。结果表明,经等离子接枝PAA处理后,复合材料的ILSS有了很大提高。SEM显示经接枝处理后CF和PAA树脂之间的界面结合紧密,改善了复合材料的界面结合性能。     

pePC-SAFT: Modeling of polyelectrolyte systems: 1. Vapor–liquid equilibria

A molecular thermodynamic model for polyelectrolyte systems—called pePC-SAFT—is proposed. The effect of charged monomers within the polyelectrolyte chain is explicitly taken into account in the reference term by replacing the hard-chain contribution of the PC-SAFT model by a charged-hard-chain contribution. Moreover, counterion condensation is accounted for to determine the effective number of charges along the polyion as well as of free counterions. The electrostatic contribution of the free counterions is described by a Debye–Hückel term.     

电场条件下高分子共混物组分浓度梯度化的研究

研究了聚乙烯醇/聚丙烯酸高分子共混物水溶液中,共混物各组分在电场诱导条件下沿电场方向的浓度梯度分布情况.通过测定不同时刻PVA/PAA高分子共混物水溶液在电场的不同区域内的pH值,研究了电场诱导下共混物各组分沿电场方向的迁移过程.结果表明,PAAn-向电场正极迁移,同时由于浓差梯度,PVA向负极迁移,并形成浓度梯度分布.随时间的延长,高分子共混物的组分梯度程度逐渐加大.     

Thermal conductivity and thermal diffusivity of poly(acrylic acid) by transient hot wire technique

The paper describes a new transient hot wire instrument which employs 25.4 μm diameter tantalum wire with an insulating tantalum pentoxide coating. This hot-wire cell with a thin insulating layer is suitable for measurement of the thermal conductivity and the thermal diffusivity of electrically conducting and polar liquids. This instrument has been used for experimental measurement of the thermal conductivity and the thermal diffusivity of poly(acrylic acid) solution (50 mass%) in the temperature range of 299 to 368 K at atmospheric pressure. The thermal conductivity data is estimated to be accurate within ±4%. Thermal diffusivity measurements have a much higher uncertainty (±30%) and need further refinement.     

梯度引发自由基聚合体系(Ⅰ)——基原法合成超高分子量聚合物

90年代在自由基聚合基础研究领域的一个重要成是“长 短终止”理论被进一步确认和接受[1 ,2 ] .按照该模型 ,聚合反应中的终止反应主要发生在长链自由基与短链自由基或初级自由基之间 ,即长链自由基之间很难进行终止反应 ,链终止常数随链长增加而急剧下降 .80年代初 ,Ｓｉｍｉｏｎｅｓｃｕ等[3] 曾报道了用等离子体照射封有单体的玻璃管 ,尔后放入暗处聚合的工作 ,发现不仅可得到分子量上千万的聚丙烯酸或聚丙烯酰胺 ,而且聚合活性可保持几十个小时 ;国内学者[4] 利用该法也得到了分子量接近千万的聚丙烯酰胺 .基于这种终止模型和实验结果 ,…     

Analysis of the specific heat of p-azoxyanisole (PAA) near the phase transitions

The analysis of the experimental data for the specific heat C_p at various temperatures is given here near the nematic-isotropic liquid (T_NI = 133.9°C) and the solid-nematic (T_SN = 117.6°C) transitions in p-azoxyanisole (PAA). The analysis of the specific heat C_p is performed according to a simple power-law formula and a renormalisation-group expression. The values of the critical exponent α are extracted above and below the transition temperatures of T_NI and T_SN for this liquid crystalline material. Our exponent values are compared with the predictions of a three-dimensional Ising model and XY model for liquid crystals. Using the specific heat C_p , the temperature dependence of the enthalpy H and the entropy S is calculated in the nematic phase (T > T_SN ) of p-azoxyanisole.