A Luminescent Dicyanodistyrylbenzene-based Liquid Crystal Polymer Network for Photochemically Patterned Photonic Composite Film

A novel photonic composite film based on a luminescent dicyanodistyrylbenzene-based liquid crystal polymer network (LCN)was fabricated by using a silica colloidal crystal as a template.The upper part of inverse opal structure and the luminescence characteristics of dicyanodistyrylbenzene-based moiety endowed the resulting bilayer photonic film with structural color arising from coherent Bragg reflection and fluorescence properties,respectively.A fluorescence enhancement phenomenon was observed in the photonic film due to the overlap between the reflection band and emission band of the fluorescent LCN.More importantly,the photo-induced irreversible Z/E photoisomerization of dicyanodistyrylbenzene-based moiety in the photonic film led to both a reflection spectral shift and an observable fluorescence variation.On the basis of this effective phototuning process,microscopic patterning ofphotonic film was developed under both fluorescence mode and reflection mode.The work demonstrated here provides a new route to construct photo-responsive photonic film.     

Development of a thickness shear mode acoustic sensor based on an electrosynthesized molecularly imprinted polymer using an underivatized amino acid as the template

The preparation and characterization of electrosynthesized poly(o-phenylenediamine) (iPoPD) as a molecular imprinting material were studied by an in situ quartz crystal impedance method. The changes of delta f0, delta R1, delta L1 and delta C0 suggest that the polymer film was compact and rigid. The thickness shear mode (TSM) acoustic sensor modified with this material exhibits molecular recognition ability to the template molecule of DL-phenylalanine. In the range 2-20 mM, a linear relationship between the frequency shift delta f0 and logC was found from the calibration graph. Scatchard analysis of the relevant calibration graph offers information on the equilibrium of the binding interaction and the recognition sites. Using this electropolymerization technology, the preparation of the sensor was very simple and the reproducibility of preparation was very good. In particular, it offers possibilities for sensor miniaturization.     

Halogen bonding as a new driving force for layer-by-layer assembly

A new approach for fabricating a layer-by-layer polymer film was explored, which was based on the halogen bonding between poly(4-(4-iodo-2,3,5,6-tetrafluorophenoxy)-butyl acrylate) and poly(4-vinylpyridine). Layer-by-layer assembly of two polymers was confirmed by UV-vis spectroscopy and quartz crystal microbalance measurements. The interaction between the two polymers was identified as halogen bonding by X-ray photoelectron spectroscopy. The surface of the multilayer film is flat, and the thickness of one bilayer is about 1.3 nm. We also compared the stability of a halogen-bonded multilayer film in methanol with that of a hydrogen-bonded multilayer film.     

Resonant multisensor system for high-throughput determinations of solvent/polymer interactions

Solvent-resistant polymers are important in numerous research, engineering, and consumer applications. To address the limitations of existing methods of evaluation of polymer solubility and solvent resistance, we developed and built a 6 x 4 array of resonant acoustic-wave sensors operating in the thickness shear mode (TSM). The application of this system makes possible analysis of nanogram quantities of polymers in small amounts of solvent and permits the simultaneous analysis of multiple samples, such as those produced in combinatorial polymerization reactions. These parallel determinations of polymer/solvent interactions eliminate errors associated with serial determinations. During the periodic exposure of the TSM crystals to polymer/solvent combinations, the mass increase of the crystal is determined, which is proportional to the amount of polymer dissolved and deposited onto the sensor from a polymer solution. We demonstrate our sensor system for reliable quantification of solubility of several types of polymers in various solvents. The high mass sensitivity of our resonant TSM sensors (10 ng), use of only a minute volume of a solvent (< 2 mL), and parallel operation (matching a layout of available 24 well plates) make this system a good fit with available polymer combinatorial synthesis equipment.     

Piezoelectric crystal for sensing bacteria by immobilizing antibodies on divinylsulphone activated poly-m-aminophenol film

A polymer sorbent formed at the surface of gold-plated piezoelectric crystal by anodic oxidation of m-aminophenol was investigated by voltammetric, FTIR techniques for antibody coupling after activation by divinylsulphone. A novel film with increased capacity for immobilizing antibodies was obtained using phloroglucinol to modify poly-m-aminophenol via divinylsulphone. Compared with the dip-coating methods using polyethylenimine and (gamma-aminopropyl)trimethoxysilane, this new technique gave more reproducible results for the immobilization of antibody from sample to sample due to the improved homogeneity and reproducibility of the coating. With present modification method, a piezoelectric immunosensor was developed for the detection of Salmonella enteritidis. A detection limit of 1x10(5) cells ml(-1) and an assay time of 25 min were achieved.     

Roughness correlation and interdiffusion in thin films of polymer chains

The surface morphology of thin bilayer polymer films on top of glass substrates was investigated. The bilayer consists of a blend film of protonated and deuterated polystyrene and an underlying deuterated polystyrene film. Choosing the thickness of the top film larger than 8 times and smaller than 2 times the radius of gyration of the chains enables the determination of film thickness and confinement effects. With diffuse neutron scattering at grazing incidence in the region of total external reflection, a depth sensitivity and a contrast even at the internal polymer–polymer interface was achieved. The underlying film is conformal to the substrate, and depending on the thickness of the top film two different types of roughness correlations are observed. Thin confined films nestle to the underlying polymer films, while the stiffness of thicker bulky films provides an independent morphology. In both cases, annealing above the glass-transition temperature yields an interdiffusion at the internal polymer–polymer interface, and the polymer–air surface remains essentially unchanged with respect to roughness correlations. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2862–2874, 1999     

Signal Enhancement using A Swellable Polymer TSM Acoustic Wave Sensor Coating

ABSTRACT

The generation of large changes in the crystal frequency is a highly sought-after goal in designing a successful thickness-shear mode (TSM) acoustic wave sensor application. We examined the potential for modulating the mass loading and viscoelastic properties of a swellable polymeric coating to achieve this goal. Using a 10 MHz AT-cut crystal with an immobilized coating of a styrene-divinylbenzene copolymer, a high molecular weight target analyte with complementary ionic and molecular binding properties was selected. Injection of the antibiotic cefoperazone in a sodium acetate buffer generated exceptionally large changes in frequency, in the range 500 - 5000 Hz. The rate of change in frequency is proportional to the analytical concentration. A multi-step regeneration protocol allows the coating to be reused multiple times. These results suggest that TSM sensor sensitivities can be significantly enhanced for selected analytes by the judicious selection of an appropriate swellable polymer coating.     

正丁胺等离子体膜TSM声波传感器的性能研究

等离子体聚合物在结构上与普通的聚合物显著不同,它能形成含有活性基团的高度交联的网络结构,从而具有良好的均匀性及对基质的附着性^[1,2].有关采用等离子体聚合膜的TSM传感器的报道不多^[3,4].     

Charge trapping reactions in bilayer electrodes

The cyclic voltammetric peaks for charging trapping and untrapping reactions between the inner and outer redox polymer films of five bilayer electrodes are compared to a theory for control of the rate of charge trapping by electron diffusion rates in the inner polymer film. The five bilayer electrodes use various different redox polymer films (electropolymerized poly-pyridine complexes of Fe, Ru, and Os, and polyvinylferrocene) arranged in different orders. The currents on the rising edge of the bilayer trapping and untrapping peaks follow the electron diffusion theory up to ca. 80% of the peak current; currents thereafter are controlled by another process(es). The analysis yields values for the electron diffusion constants in the inner bilayer polymer films, which agree with one another for different bilayers having the same inner film polymer films and which also agree with independent determinations by other methods. Two of the bilayers are made from the same two polymers, arranged in different inner-outer order. These bilayers also illustrate the occurrence of a “leak reaction”, in which charge trapped in the outer film is discharged via a thermodynamically unfavorable electron transfer reaction with the inner polymer film.     

Complexation of polycations to anionic liposomes: composition and structure of the interfacial complexes

Poly(N-ethyl-4-vinylpyridinium bromide) (a polycation with a degree of polymerization of 1100) was adsorbed onto liposomes composed of egg lecithin with a 0.05-0.20 molar fraction (nu) of anionic headgroups provided by cardiolipin (a doubly anionic lipid). According to electrophoretic mobility data, this led to total charge neutralization of the liposomes, whereupon the liposomes adopted a positive charge as additional polymer continued to adsorb. Although the liposomes aggregated at the charge-neutralization point, they disassembled into individual liposomes after becoming positively charged. The degree of polymer adsorption was shown to reach a limit. Thus, by measuring the free polymer content in a liposome suspension, it was possible to determine the polymer concentration at which the liposome surface became saturated with polymer. Beyond this point, an electrostatic/steric barrier at the surface suppressed further adsorption. Dynamic light scattering studies of liposomes with and without adsorbed polymer allowed calculation of the polymer film thickness which ranged from 22 to 35 nm as the molar fraction of cardiolipin (nu) increased from 0.05 to 0.20. The greater the content on the anionic lipid in the bilayer, the thicker the polymer film. The maximum number of polymer molecules adsorbed onto the liposomes was estimated: 1-2 molecules for nu = 0.05; 3 molecules for nu = 0.1; 4- molecules for nu = 0.15; and 6 molecules for nu = 0.2. The polymer appears to lie on the liposome surface, rather than embedding into the bilayer, because addition of NaCl easily dislodges the polymer from the liposome into the bulk water.     

Polymer cushions functionalized with lipid molecules

This Letter reports a novel approach to the fabrication of a biomimicking surface by modification of an end-functionalizable smooth polymer cushion constructed via chemoselective ligation with a phospholipid-like molecule containing oxyamine groups. The mobility of a phospholipid bilayer formed by vesicle fusion on the phospholipid-like molecule terminated polymer film was characterized by fluorescence recovery after bleaching. Platelet adhesion, as one measure of biocompatibility of the film was also studied and compared to other surfaces such as polyethylene or poly(dimethylsiloxane). The results show that the end-functionalized smooth polymer cushion has potential as a biocompatible platform to reconstitute membrane proteins.     

压电免疫质量传感器中生物大分子的固定化方法

评述了近十几年来压电免疫质量传感器研究中的关键技术－生物分子固定化方法的研究应用,并对固定化方法的发展予以展望。     

A study of a new TSM bio-mimetic sensor using a molecularly imprinted polymer coating and its application for the determination of nicotine in human serum and urine

A new bio-mimetic quartz crystal thickness-shear-mode (TSM) sensor, using an imprinted polymer coating as the sensitive material, has been fabricated and applied to the determination of nicotine (NIC) in human serum and urine. The molecularly imprinted polymer (MIP) was synthesized using NIC as the template molecule and methacrylic acid (MAA) as the functional monomer. The sensor showed high selectivity and a sensitive response to NIC in aqueous system. The linear response range of the sensor was between 5.0 x 10(-8) and 1.0 x 10(-4) M with a detection limit of 2.5 x 10(-8) M. The viscoelasticity of the coating in the air and in liquid has been studied by the impedance spectrum. The MIP sensor was stable and exhibited effective reproducibility. Satisfactory results were achieved in the detection of the real samples.     

Self-assembly and solid-state photo polymerization of acrylamide crystal film

Solid-state polymerization has many advantages such as solvent-free, environmental friendly, less cost, and high purity of product. In this study, a crystal film of polyacrylamide was synthesized by solid-state polymerization. Firstly, gelatin was used for inducing acrylamide to form monomer crystal film through self-assembly in an aqueous solution. Then, the monomer crystal film underwent a photo-initiating polymerization to give the corresponding polymer crystal film. The structure of the crystal film was confirmed by Fourier-transformed infrared spectrometry, X-ray diffraction, microscopic melting point detector, and differential scanning calorimeter. The morphology was observed with scanning electron microscopy. The molecular weight was measured by gel permeation chromatography. It was found that a well-organized polyacrylamide crystal film was formed by controlling the synthetic conditions. The lattice size of the crystal changed very little before and after polymerization. The crystal film displayed a fibrous shape and was well-organized.     

Free surface-induced bilayer smectic A phase in polar liquid crystals

Here the influence of the free surface on both a thick (semi-infinite) layer and a thin freely suspended film of a polar liquid crystal is investigated. It is shown that within the temperature range of the monolayer smectic A phase (S_A1) the interaction between polar molecules and the free surface of the liquid crystal gives rise to a bilayer smectic A, a structure with long range antiferroelectric order (S_A2) in the surface region of the semi-infinite layer. The dependence of the bilayer smectic order parameter on the strength of the interaction between the constituent molecules and the free surface as well as temperature and the distance to the free surface are determined. Sufficiently far from the S_A1-S_A2 transition the latter dependence has an exponential character and the depth of the S_A2 phase penetration into bulk liquid crystal is equal to the longitudinal correlation length for the bilayer smectic A structure fluctuations in the S_A1 phase. However, near the S_A1-S_A2 transition the bilayer smectic order parameter decays non-exponentially and more rapidly with increasing distance to the free surface. In addition, it is found that the bilayer S_A2 phase can form several smectic layers at the free surface of a semi-infinite polar liquid crystal layer with the S_A1 phase. Finally, it is shown that in a freely suspended film the free surface-induced S_A2 phase can completely occupy the volume of the sample. Hence in a freely suspended polar liquid crystal film the S_A1-S_A2 transition occurs with decreasing film thickness.     

Polymer-based bilayer interfaces for electrochemical rectification

In this paper, the electrochemical current rectification phenomenon exhibited at an electrochemical interface constituted by a glassy carbon electrode covered with a bilayer of polymer films is discussed. The authors have shown that Methylene Blue (MB) redox species can be confined to a very thin insulating polymer film formed from orthophenylene diamine. The poly(opd) film exhibited excellent blocking properties to redox molecules in solution. On the other hand, the insulating poly(opd) film trapped with MB could mediate electron transfer between the redox molecules in solution and the electrode. Further, a second polymeric layer (Nafion film) trapped with ferrocene redox species was formed as the outer layer over the inner poly (opd) film containing MB. This bilayer-modified electrode, due to the significant difference in the redox potentials of the MB and ferrocene species immobilized in the inner and outer layers, respectively, exhibits unidirectional current flow and the results of the voltammetric investigations on the modified electrodes are described in this communication.     

A temperature and pH double sensitive cholesteric polymer film from a photopolymerizable chiral hydrogen-bonded assembly

In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a cholesteric liquid crystal (Ch-LC) monomers mixture containing a photopolymerizable chiral H-bonded assembly (PCHA). The cholesteric polymer film based on PCHA can be thermally switched to reflect red color from the initial green/yellow color as temperature is increased, which is due to a change in helical pitch induced by the weakening of H-bonded interaction in the polymer film. Additionally, the selective reflection band (SRB) of the cholesteric polymer film in solution with pH > 7 showed an obvious red shift with increasing pH values. While the SRB of the cholesteric polymer film in solutions with pH = 7 and pH < 7 hardly changed. This pH sensitivity in solutions with pH > 7 could be explained by the breakage of H-bonds in the cholesteric polymer film and the structure changes induced by―OH and―K + ions in the alkaline solution. In contrast, it couldn’t happen in the neutral and acidic solutions. The cholesteric polymer film in this study can be used as optical/photonic papers, optical sensors and LCs displays, etc.     

Conductivity enhancement of PEDOT:PSS film via sulfonic acid modification: application as transparent electrode for ITO-free polymer solar cells

3-Hydroxy-1-propanesulfonic acid(HPSA)was applied as a modification layer on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)film via spin-coating,resulting in a massive boost of the conductivity of PEDOT:PSS film,and thus the as-formed PEDOT:PSS/HPSA bilayer film was successfully used as a transparent electrode for ITO-free polymer solar cells(PSCs).Under the optimized concentration of HPSA(0.2 mol L~(-1)),the PEDOT:PSS/HPSA bilayer film has a conductivity of 1020 S cm~(-1),which is improved by about 1400 times of the pristine PEDOT:PSS film(0.7 S cm~(-1)).The sheet resistance of the PEDOT:PSS/HPSA bilayer film was 98Ωsq~(-1),and its transparency in the visible range was over 80%.Both parameters are comparable to those of ITO,enabling its suitability as the transparent electrode.According to atomic force microscopy(AFM),UV-Vis and Raman spectroscopic measurements,the conductivity enhancement was resulted from the removal of PSS moiety by methanol solvent and HPSA-induced segregation of insulating PSS chains along with the conformation transition of the conductive PEDOT chains within PEDOT:PSS.Upon applying PEDOT:PSS/HPSA bilayer film as the transparent electrode substituting ITO,the ITO-free polymer solar cells(PSCs)based on poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]:[6,6]-phenyl C71-butyric acid methyl ester(PC_(71)BM)(PCDTBT:PC_(71)BM)active layer exhibited a power conversion efficiency(PCE)of 5.52%,which is comparable to that of the traditional ITO-based devices.     

Determination of surface area and porosity of small, nanometer-thick films by quartz crystal microbalance measurement of gas adsorption

The Brunauer-Emmett-Teller (BET) surface area of 15 nm-thick films made of TiO2/polyelectrolyte bilayer was determined by quartz crystal microbalance (QCM) measurement of N2 and Ar adsorption isotherms at 77 K. The measurements were carried out using a home-built vacuum chamber that includes built-in 9 MHz QCM and cryostat units. As little as 1 ng of the adsorbed gas could be detected, and the BET surface area of a flat Au film (ca. 0.5 cm2) on an oscillator was determined within an experimental error of +/-5%. The titania/polymer composite film gives N2 and Ar adsorption isotherms consisting of a less-pronounced type-I curve and a break at around p/p0 = 0.7. This behavior is ascribed to the presence of irregular micropores and 6 nm phi-mesopores in the composite film. An analysis of the isotherms shows that the porosity of the composite film is about 12%, which is much smaller than that of bulk titania gel powder. The greater density appears to be related to the reported superior properties (robustness and resistance to electrical breakdown) of the organic/inorganic multilayer film. We conclude that the QCM-based, high-precision measurement of gas adsorption is a powerful tool for investigation of the detailed morphology of nanometer-thick films.     

Facile fabrication of mechanochromic-responsive colloidal crystal films

This paper presents a simple approach to fabricate a reversible mechanochromic-responsive crystal film based on the room-temperature film-formation of monodisperse polymer latex by the aid of nanosilica particles. In this approach, when the "soft" colloidal polymer spheres were blended with colloidal silica particles and then cast on a substrate, followed by drying at room temperature for self-assembly, an elastic crystal film was directly obtained. This crystal film has not only reversible and repeatable mechanochromic-responsive property, but also tunable color and peak position covering almost entire visible spectral region, depending upon the sizes of polymer spheres and strains. This optical response is attributed to the variation of lattice spacing during deformation.