Quartz crystal microbalance sensor for organic vapor detection based on molecularly imprinted polymers

Molecularly imprinted polymers on quartz crystal microbalances (QCM) are examined for their ability to detect vapors of small organic molecules with greater sensitivity and selectivity than the traditional amorphous polymer coatings. Hydroquinone and phenol serve as noncovalently bound templates that generate shape-selective cavities in a poly(acrylic) or poly(methacrylic) polymer matrix. The imprinted polymers are immobilized on the piezoelectric crystal surface via a precoated poly(isobutylene) layer. The behavior of the imprinted polymer films is characterized by the dynamic and steady-state response of the QCM frequency to pulses of organic vapors in dry air. The apparent partition coefficients are determined for imprinted and nonimprinted polymers prepared by two synthetic methods and for varying mole ratios of template to monomer. The hydroquinone-imprinted polymers and, to a lesser extent, the phenol-imprinted polymers exhibit greater sensitivity and higher selectivity than the nonimprinted polymers toward organic vapors that are structurally related to the templates. These results indicate that molecularly imprinted polymers are promising for the development of selective piezoelectric sensors for organic vapor detection.     

A study of Langmuir-Blodgett thin film for organic vapor detection

In this work, arachidic acid was deposited onto a quartz crystal using a standard Langmuir-Blodgett (LB) thin film deposition procedure. Quartz Crystal Microbalance (QCM) technique was used to monitor the reproducibility of the LB film monolayer and was employed to study the organic vapor sensing properties of chloroform, toluene, benzene, ethyl alcohol and isopropyl alcohol. QCM results show that arachidic acid monolayer was successfully organised and deposited from the water surface onto a quartz crystal substrate. This LB film is found to be highly sensitive and selective to chloroform vapor than other vapors. The response of the sample against chloroform is fast, large and reversible.     

Electroless metallization of organic polymers using the polymer as a redox reagent: Reaction of polyimide with zintl anions

A facile general scheme for the metallization of polyimides (PIm) and certain other organic polymers is presented. The driving force for the metallization is the extremely strong reducing power of the polyatomic main group anions, the so-called Zintl anions.The polymide can be metallized with many main group elements (e.g. germanium, tin, lead, arsenic, antimony), by simply treating the PIm with solutions obtained from the extraction of potassium-main group alloys. The metal films are formed by the topochemical oxidation of the anionic clusters by the polyimide. The reaction proceeds by a reduction-intercalation-deposition mechanism where the PIm is reduced to monoanions and dianions, the Zintl anion's alkali metal counteraction intercalates the polymer to balance the charge from the reduction and the clusters are oxidized to the metallic state on the polymer surface.The polyimide metallization has been extended to certain transition metals by employing a method that is conceptually the reverse of main group metallizations discussed above (i.e. using the PIm as a reducing agent toward an oxidized metal species in solution). Specifically, the treatment of PIm with methanol solutions of K₄SnTe₄ gives intercalated material, K_x·PIm, with no surface metallization. The reaction of K_x·PIm with solutions of transition metal cations with reduction potentials more positive than that of K_x·PIm results in metal deposition.The preparation of surfaces containing two metals, by a combination of the two above methods, will be discussed.     

聚醚嵌段酰胺膜在有机蒸气回收中的应用

介绍了以聚醚嵌段酰胺(PEBA)膜材料制备出的分离膜在有机蒸气回收方面的应用。分别从材料的特点、分离膜的制备方法以及膜的分离性能等方面进行分析,表明PEBA这种新型膜材料在有机蒸气回收方面的优良性能。并对复合分离膜的底衬阻力对复合膜分离性能的影响进行了分析,最后对气体膜分离在有机蒸气回收中的应用进行展望。     

Thermo-mechanical analysis of dental silicone polymers

Soft lining materials are used to replace the inner surface of a conventional complete denture, especially for weak elderly patients, with delicate health who cannot tolerate the hard acrylic denture base. Most of these patients have fragile supporting mucosa, excessive residual ridge resorption, particularly on the mandibular arch. The application of a soft liner to the mandibular denture allows absorbing impact forces during mastication and relieving oral mucosa. Actually, the silicone rubbers constitute the main family of commercialised soft lining materials. This study was conducted to understand the relationships between the mechanical properties and the physical structure of polysiloxanes. For this purpose, a series of polysiloxanes of various chemical compositions have been investigated. The evolution of their physical structure as a function of temperature has been followed by differential scanning calorimetry (DSC). In order to facilitate comparisons, the mechanical modulus has been analysed upon the same heating rate using dynamic mechanical analysis (DMA). Polysiloxanes actually commercialised as soft denture liners are three-dimensional networks: the flexibility of chains allows a crystalline organisation in an amorphous phase leading to the low value of the shear modulus. The dynamic mechanical analysis shows that they are used in the rubbery state. So, polysiloxanes have steady mechanical properties during physiological utilisation.     

有机硅改性聚合物的研究进展

从共聚改性、接枝改性和共混改性等几个方面简要介绍了有机硅改性聚合物的研究状况和发展历程.     

Nanoindentation strain rate sensitivity of thermo-oxidized PMR-15 polyimide

This article reports the study of rate-dependent mechanical properties of thermal-oxidized PMR-15 polyimide resins with a nanoindenter. A series of PMR-15 resin specimens have been isothermally aged at various temperatures, times, and pressures. The strain rate sensitivity of oxidized surface layer obtained at each aging condition has been determined from nanoindentation creep experiments using constant displacement-rate method. Results show that the average strain rate sensitivity in the oxidized surface layer is notably higher than that in the unoxidized interior, indicating that the oxidized surface layer has limited ductility and thus is susceptible to fracture. Effects of aging environments (time, temperature, and pressure) on mechanical properties are also examined. After passing the initial oxidation stage, the change in strain rate sensitivity become insignificant and less sensitive to aging parameters.     

Water vapor detection with individual tin oxide nanowires

Individual tin oxide nanowires (NWs), contacted to platinum electrodes using focused ion beam assisted nanolithography, were used for detecting water vapor (1500-32?000?ppm) in different gaseous environments. Responses obtained in synthetic air (SA) and nitrogen atmospheres suggested differences in the sensing mechanism, which were related to changes in surface density of the adsorbed oxygen species in the two cases. A model describing the different behaviors has been proposed together with comparative evaluation of NW responses against sensors based on bulk tin oxide. The results obtained on ten?individual devices (tested >6 times) revealed the interfering effect of water in the detection of carbon monoxide and illustrated the intrinsic potential of nanowire-based devices as humidity sensors. Investigations were made on sensitivity, recovery time and device stability as well as surface-humidity interactions. This is the first step towards fundamental understanding of single-crystalline one-dimensional (1D) tin oxide nanostructures for sensor applications, which could lead to integration in real devices.     

Optimum detection of multiple vapor materials with frequency-agile lidar

Differential absorption lidar (DIAL) is a well-established technology for estimating the concentration and its path integral CL of vapor materials using two closely spaced wavelengths. The recent development of frequency-agile lasers (FAL's) with as many as 60 wavelengths that can be rapidly scanned motivates the need for detection and estimation algorithms that are optimal for lidar employing these new sources. I derive detection and multimaterial CL estimation algorithms for FAL applications using the likelihood ratio test methodology of multivariate statistical inference theory. Three model sets of assumptions are considered with regard to the spectral properties of the backscatter from either topographic or aerosol targets. The calculations are illustrated through both simulated and actual lidar data.     

Facile surface modification of silicone rubber with zwitterionic polymers for improving blood compatibility

A facile approach to modify silicone rubber (SR) membrane for improving the blood compatibility was investigated. The hydrophobic SR surface was firstly activated by air plasma, after which an initiator was immobilized on the activated surface for atom transfer radical polymerization (ATRP). Three zwitterionic polymers were then grafted from SR membrane via surface-initiated atom transfer radical polymerization (SI-ATRP). The surface composition, wettability, and morphology of the membranes before and after modification were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (WCA) measurement, and atomic force microscopy (AFM). Results showed that zwitterionic polymers were successfully grafted from SR surfaces, which remarkably improved the wettability of the SR surface. The blood compatibility of the membranes was evaluated by protein adsorption and platelet adhesion tests in vitro. As observed, all the zwitterionic polymer modified surfaces have improved resistance to nonspecific protein adsorption and have excellent resistance to platelet adhesion, showing significantly improved blood compatibility. This work should inspire many creative uses of SR based materials for biomedical applications such as vessel, catheter, and microfluidics.     

Modeling potentiometric sensitivity of conducting polymers

The influence of different polymerization conditions and electrochemical processes provoked by soaking on the potentiometric sensitivity of conducting polymer films is discussed. Poly(pyrrole) doped with hexacyanoferrate(II) is selected as a model polymer. It is shown that, depending on the conditions applied during film deposition and soaking, either anionic or cationic potentiometric responses can be observed and related to the composition of the film. The potentiometric sensitivity of the conducting polymer films is analyzed and interpreted by means of generalized theoretical schema.     

Efficiency enhancement in organic solar cells with ferroelectric polymers

The recombination of electrons and holes in semiconducting polymer-fullerene blends has been identified as a main cause of energy loss in organic photovoltaic devices. Generally, an external bias voltage is required to efficiently separate the electrons and holes and thus prevent their recombination. Here we show that a large, permanent, internal electric field can be ensured by incorporating a ferroelectric polymer layer into the device, which eliminates the need for an external bias. The electric field, of the order of 50 V μm(-1), potentially induced by the ferroelectric layer is tens of times larger than that achievable by the use of electrodes with different work functions. We show that ferroelectric polymer layers enhanced the efficiency of several types of organic photovoltaic device from 1-2% without layers to 4-5% with layers. These enhanced efficiencies are 10-20% higher than those achieved by other methods, such as morphology and electrode work-function optimization. The devices show the unique characteristics of ferroelectric photovoltaic devices with switchable diode polarity and tunable efficiency.     

聚醚、氨基改性有机硅乳液的研制

采用乳液聚合合成聚醚、氨基改性有机硅乳液,讨论了乳化剂、催化剂、改性剂用量及反应温度、反应时间对乳液聚合的影响;采用水相和逆相乳化法制得有机硅微乳液,并讨论了乳液的性能。     

Bioimprinting of polymers and sol-gel phases. Selective detection of yeasts with imprinted polymers

Coated quartz crystal microbalances were modified with a surface-imprinting process using whole yeast cells. These molded polymer and sol-gel surfaces show honeycomb-like structures as shown by atomic force microscopy. Reinclusion of cells allows a selective on-line monitoring of these microorganism concentrations in water over 5 orders of magnitude. The sensitivity to cells holds up in growth media up to 21 g/L. Even cell fragments can be detected in flowing conditions. The highly robust polymers on the sensor devices are suitable for biotechnological applications.     

膜技术在有机蒸气回收中的工业应用

介绍了有机蒸气分离膜的分离原理，并分别介绍了有机蒸气分离膜在石油化工、聚氯乙烯行业中的应用．     

蒸汽渗透法有机溶剂气相脱水

蒸汽渗透法是一种膜法气相脱水技术，与渗透汽化不同，在该过程中，进料的蒸汽与膜直接接触，在高于料液沸点的温度下进行操作，可以采用提高压力和温度等手段提高分离膜的透过通量，并可以与分馏过程集成使用，简化化工操作单元，要求所使用的膜具有更好的高温耐溶性性能。文章综述近几年２５篇有关文献，介绍蒸汽渗透过程的特点、与渗透汽化的对比、使用的膜以及其应用前景。     

有机硅耐磨涂料改性的研究进展

综述了有机硅耐磨涂料的改性方法,介绍了其在各领域中的运用,阐明了有机硅耐磨涂料改性研究与应用新进展.     

Wavelength modulation detection of water vapor with a vertical cavity surface-emitting laser

A vertical cavity surface-emitting laser was studied for gas-sensing applications. Properties of the 962-nm laser that were measured include side-mode suppression, wavelength tuning with temperature and current, power versus injection current, and the amplitude noise spectrum. With wavelength modulation spectroscopy, a rms noise level of 2 x 10(-4) absorbance units was achieved. The large current tuning range (25 cm(-1)) and smaller amplitude modulation (11%/cm(-1)) of the vertical cavity laser compare favorably with Fabry-Perot and distributed feedback diode lasers for spectroscopic gas sensing, especially at atmospheric pressure.