Thermoelectrochemical Impedance of an Electrode System Metal/Conducting Polymer/Solution

For a conducting-polymer-based electrode, the temperature coefficient of potential (thermoelectrochemical impedance) is calculated for a wide range of frequencies at which the electrode temperature relative to the solution bulk varies. The obtained frequency spectra depend on the potential distribution between the metal/polymer and polymer/solution interfaces, as well as on the heat transfer conditions in the polymer film and solution.     

COMPARTMENTALIZATION OF ZINQII) TETRAPHENYLPORPHYRIN IN A HYDROPHOBIC MICRODOMAIN OF AN AMPHIPHILIC POLYELECTROLYTE: A PHYSICOCHEMICAL MODEL OF BIOLOGICAL METALLOPORPHYRIN SYSTEMS

Abstract— Small mole fractions of zinc(II) tetraphenylporphyrin (ZnTPP) moieties were covalently incorporated into amphiphilic polysulfonates having bulky hydrophobic groups such as lauryl, cyclododecyl, and (2-naphthyi)methyl (Np) groups in their side chains. The ZnTPP moieties are "compartmentalized" in the hydrophobic domains of these amphiphilic polyelectrolytes in aqueous solution. For comparison, the ZnTPP moieties were covalently incorporated into a polysulfonate without hydrophobic groups. The ZnTPP moieties in this reference polymer are exposed to water in aqueous solution. The compartmentalized ZnTPP systems in aqueous fluid solution emitted phosphorescence and thermally activated delayed fluorescence at room temperature. This is due to an extremely long-lived triplet excited state in the compartmentalized systems at room temperature in aqueous solution, e.g. 19 ms for ZnTPP compartmentalized in Np domains, compared with 3 ms for ZnTPP in the reference polymer. These remarkable compart-mentalization effects may be attributed to a restriction of motional freedom of the ZnTPP moiety isolated in a rigid and hydrophobic microenvironment provided by the amphiphilic polyelectrolytes in aqueous solution.     

A viscosity self-oscillation of polymer solution induced by the Belousov-Zhabotinsky reaction under acid-free condition

We succeeded in measuring a viscosity self-oscillation induced by the Belousov-Zhabotinsky (BZ) reaction for a polymer solution on the constant temperature condition under acid-free condition. The polymer chain is consisted of N-isopropylacrylamide, ruthenium complex as a catalyst of the BZ reaction, and an acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and the solubility control site. The viscosity self-oscillation for the AMPS-containing polymer solution was attributed to the difference between viscosities for the polymer solution in the reduced and oxidized states. The effects of the polymer concentration and the temperature of the polymer solution on the viscosity self-oscillation were investigated. As a result, the viscosity self-oscillating behavior significantly depended on the polymer concentration and the temperature of the polymer solution. The period of the viscosity self-oscillation decreased with increasing temperature in accordance with the Arrenius equation.     

Aqueous phase separation in giant vesicles

We report the synthesis and initial characterization of approximately 10 mum diameter lipid vesicles that contain two distinct aqueous phases. The aqueous two-phase system is a dextran/poly(ethylene glycol) solution that exhibits temperature-dependent phase behavior. Vesicles were prepared above the phase transition temperature of the polymer solution. Upon cooling to room temperature, the polymer solution phase separated both within the vesicles and in the bulk solution. The location of poly(ethylene glycol)-rich and dextran-rich phases was determined by fluorescence microscopy. These structures are exciting in that they enable for the first time the interior volume of liposomes to be structured.     

Effects of Hofmeister Anions on the LCST of PNIPAM as a Function of Molecular Weight

The effect of a series of sodium salts on the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide), PNIPAM, was investigated as a function of molecular weight and polymer concentration with a temperature gradient microfluidic device under a dark-field microscope. In solutions containing sufficient concentrations of kosmotropic anions, the phase transition of PNIPAM was resolved into two separate steps for higher molecular weight samples. The first step of this two step transition was found to be sensitive to the polymer's molecular weight and solution concentration, while the second step was not. Moreover, the binding of chaotropic anions to the polymer was also influenced by molecular weight. Both sets of results could be explained by the formation of intramolecular and intermolecular hydrogen-bonding between polymer chains. By contrast, the hydrophobic hydration of the isopropyl moieties and polymer backbone was found to be unaffected by either the polymer's molecular weight or solution concentration.     

发蓝光材料聚烷基芴的合成和性能研究

聚芴及其衍生物是一类极具光、电活性的重要有机聚合物材料 .早在 90年代初 ,Fukuda等[1,2 ]首先报道了聚芴的合成 .在过去的几年中 ,由于这类聚合物及其衍生物卓越的光电性能 ,使其在发光二极管、激光器件、导电光刻蚀、光电池、生物传感器件等方面得到了广泛应用 ,从而推动了这一领域的飞速发展 .国外研究者在这方面进行了大量的研究工作 ,合成了一系列具有光电性能的聚芴共聚物 ,并用于研制各种光电器件[3～ 10 ] .从单体合成方法来看 ,大多都有采用文献 [1 ]所述的方法 ,但该方法要求在无水 (正丁基锂 )、无氧 (Ar气 )、低温 ( - 78℃ …     

Self-oscillation of polymer chains induced by the Belousov-Zhabotinsky reaction under acid-free conditions

A novel self-oscillating polymer was prepared by utilizing the Belousov-Zhabotinsky (BZ) reaction. In this study, a sulfonic acid group was newly introduced as a pH-control site into the copolymer of N-isopropylacrylamide, and the ruthenium complex was introduced as a catalyst site. By introducing the pH-control site, we succeed in causing the soluble-insoluble self-oscillation of the polymer solution under acid-free conditions in which only two BZ substrates, malonic acid and sodium bromate, were present as added agents. The self-oscillating behavior was remarkably influenced by the temperature and polymer concentration, which reflects the intermolecular aggregative capacity of the polymer chains in the reduced state to change the lower critical solution temperature. This achievement of self-oscillation of polymer chains under acid-free conditions may lead to their practical use as novel biomimetic materials under biological conditions.     

Preparation and spectroscopic properties of multiluminophore luminescent oxygen and temperature sensor films

A new luminescent oxygen and temperature sensor has been developed that utilizes two luminescent dyes, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin platinum(II) (PtTFPP, the oxygen sensor) and tris(1,10-phenanthroline)ruthenium(II) dichloride (Ruphen, the temperature sensor). The two dyes are dispersed in an oxygen-permeable polymer binder consisting of a copolymer of 4-tert-butylstyrene (tBS) and 2,2,2-trifluoroethyl methacrylate (p-tBS-co-TFEM). To alleviate energy transfer and other quenching interactions between the two luminescent dyes in the p-tBS-co-TFEM binder, the Ruphen temperature sensor is encapsulated in polyacrylonitrile (PAN) polymer nanospheres that are prepared by coprecipitation of PAN and Ruphen from N,N-dimethylformamide solution. The temperature and air-pressure response of the emission from the sensor film is fully characterized by using emission spectroscopy. The emission from the two luminescent dyes is spectrally well-separated. The intensity of the Ruphen emission varies strongly with temperature (approximately 1.4% degrees C(-1)), whereas the intensity of the PtTFPP emission varies with temperature and air pressure. The two-dye luminescent coating is useful as a pressure-sensitive paint (PSP), where the emission from the Ruphen temperature sensor is used to correct for the temperature dependence of the pressure response of the PtTFPP sensor. To demonstrate the PSP application, a coupon coated with the sensor was imaged using a CCD camera, and the CCD images were analyzed by intensity ratio methods. Spectroscopic studies were also carried out on a sensor that contains three dyes in order to demonstrate the feasibility of including an intensity reference dye along with the temperature and pressure dyes into the sensor.     

Effect of solute hydrophobicity on phase behaviour in solutions of thermoseparating polymers

 Two-phase systems consisting of a polymer rich phase and polymer depleted phase, where the polymer is either ethyl(hydroxy ethyl)cellulose (EHEC) or Ucon (a random copolymer of ethylene oxide and propylene oxide), have been studied. Both of these polymers can be separated from an aqueous solution by either temperature increase or addition of cosolutes. The polymers are thermoseparating and phase separate in water solutions at the cloud point temperature. Two types of EHEC have been studied: one with a cloud point at 60 °C and the other at 37 °C. The Ucon polymer used in this study has a cloud point at 50 °C. Ternary phase diagrams of polymer/water/cosolute systems have been investigated. When a strongly hydrophilic or hydrophobic cosolute is added to an EHEC- or Ucon–water solution, a phase separation occurs already at, or below, room temperature. As cosolutes, hydrophobic molecules like phenol, butyric and propionic acid, and hydrophilic molecules like glycine, ammonium acetate, sodium carboxylates (acetate to valerate), were studied. The polymer rich phase formed when mixing polymer, water and cosolute was strongly enriched or depleted with hydrophobic or hydrophilic cosolutes, respectively. The two phase region increased for propionic acid, butyric acid and phenol as a result of increased cosolute hydrophobicity. The opposite occurred in the series sodium acetate, sodium butyrate and sodium valerate. The effect of temperature on the phase behaviour has also been investigated. Model calculations based on Flory–Huggins theory of polymer solutions are presented, in form of a phase diagram, which semiquantitatively reproduce some experimental results. Received: 5 July 1996 Accepted: 4 November 1996     

Analytical quality solid-state composite reference electrode manufactured by injection moulding

An injection moulding method was used for fabricating solid-state reference electrodes (Ag/AgCl type) based on a polymer/inorganic salt composite. In this method, a silver/silver chloride wire was placed inside a mould into which the mixture of polymer and inorganic salt was injected. The obtained solid-state composite reference electrodes were extensively tested to study the influence of different parameters such as solution composition, the concentrations and mobility of ions and pH on the potential stability of the electrodes. These experiments revealed that the composite reference electrodes are insensitive to the matrix effect, have excellent potential readings stability and considerably reduced leakage of inorganic salt. The composite reference electrodes were compared favourably to high-quality commercial reference electrodes. It was concluded that the composite reference electrodes obtained by injection moulding are of analytical quality allowing for continuous, prolonged and intensive usage.     

Application of Ultrasonic Attenuation Measurements in the Studies on Macromolecular Conformational Behaviors——Phase Behavior of the Aqueous Solution of Poly(vinyl methyl ether) Sensitive to Temperature and the Modification of the Behavior by Using Pol

Introduction Studies on the conformational and aggregation be-haviors of macromolecules in aqueous solution and at solid/liquid interfaces have been highlighted in colloid and interface science since the early 1990s.1-3 It was mentioned in the first part of this series of studies that development of new methods, which are characterized by being in time and non-destructive and can be used for monitoring the conformational and aggregation be-havior of macromolecules, is of critical importance fo…     

Application of Ultrasonic Attenuation Measurements in the Studies on Macromolecular Conformational Behaviors

——Phase Behavior of the Aqueous Solution of Poly(vinyl methyl ether) Sensitive to Temperature and the Modification of the Behavior by Using Poly(acrylic acid) The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation measurements and fluorescence probe techniques. It has been observed that PVME solution is transparent at room temperature and becomes turbid upon heating. The solution turns clear again as soon as the temperature is decreased to room temperature. The heating and cooling process can be repeated for many times. The phase behavior of the solution sensitive to temperature is attributed to the conformational changes of the polymer. PVME may adopt an open coil conformation at room temperature. With this conformation, the polymer is well miscible with the solvent, water, and thereby the system is a real solution. The polymer may adopt a compact coil conformation when the temperature is higher than a specific value, which is called the LCST (the lower critical solution temperature) of PVME. In this case, the polymer tangles to each other and forms various aggregates, which can scatter incident light and ultrasonic waves greatly, resulting in the phase separation. Introduction of PAA decreases the temperature sensitivity of the phase behavior of the polymer. The nature of the inhibition is attributed to the complexation of PAA with PVME and the strong hydrophilicity of PAA. Results from fluorescence probe studies are in accordance with those from ultrasonic attenuation measurements, indicating again that the ultrasonic attenuation method can be successfully used for the qualitative studies of polymer conformations and complexation between polymers.     

Probing the dielectric environment surrounding poly(N-isopropylacrylamide) in aqueous solution with covalently attached spirobenzopyran

The dielectric environment surrounding poly(N-isopropylacrylamide) in aqueous solution was investigated by probing with spirobenzopyran covalently attached as a side chain to the polymer main chain. Inherent characteristics of the spirobenzopyran chromophore were analyzed, and the chromophore was confirmed to be suitable to probe the local polar condition around the polymer. Measurements for an aqueous polymer solution at various temperatures elucidated that the dielectric environment surrounding the polymer changed continuously even in the temperature range far below the lower critical solution temperature. This result suggested that the local and weak orientation of water molecules around the polymer diminished continuously in a preliminary stage of shifting to thermally induced phase separation. The dielectric environment surrounding thermoresponsive polymer in aqueous solution was investigated by probing with spirobenzopyran covalently attached as a side chain to the polymer main chain.     

Interactions between nanocolloidal particles in polymer solutions: effect of attractive interactions

We present a density-functional theory study of nanoparticle interactions in a concentrated polymer solution. The polymers are modeled as freely jointed tangent chains; all nonbonded interactions between polymer segments and nanoparticles are described by Lennard-Jones potentials. We test several recently proposed methods of treating attractive interactions within the density-functional theory framework by comparing theoretical results with recent simulation data. We find that the simple van der Waals approach provides the most accurate results for the polymer-mediated potential of mean force between two dilute nanoparticles. We employ this approach to study nanoparticle interactions as a function of nanoparticle-segment interaction strength and polymer solution density and temperature.     

Liquid-liquid equilibria and theta temperatures in homopolymer-solvent solutions from a perturbed hard-sphere-chain equation of state

The perturbed hard-sphere-chain (PHSC) equation of state is used to calculate liquid-liquid equilibria of binary nonpolar solvent/homopolymer systems exhibiting both an upper critical solution temperature (UCST) and a lower critical solution temperature (LCST). Systems studied include polyisobutylene, polyethylene, and polystyrene solutions. Equation-of-state parameters of homopolymers are obtained by regressing the pressure-volume-temperature data of polymer melts. In polymer solutions, however, theory overestimates the equation-of-state effect which causes the LCST at elevated temperature. To correct the overestimated equation-of-state effect, an empirical adjustable parameter is introduced into the perturbation term of the PHSC equation of state. An entropy parameter is also introduced into the Helmholtz energy of the mixture to correlate quantitatively the dependence of critical temperatures on polymer molecular weight. For systems exhibiting a LCST, two adjustable parameters are required to obtain quantitative agreement of theoretical critical temperatures with experiment as a function of polymer molecular weight. For systems exhibiting both an UCST and a LCST, three adjustable parameters may be necessary. The need for so many empirical binary parameters is probably due to the oversimplified perturbation term which is based on the mean-field assumption. © 1996 John Wiley & Sons, Inc.     

Temperature-dependent competition between adsorption and aggregation of a cellulose ether--simultaneous use of optical and acoustical techniques for investigating surface properties

Adsorption of the temperature-responsive polymer hydroxypropylmethylcellulose (HPMC) from an aqueous solution onto hydrophobized silica was followed well above the bulk instability temperature (T(2)) in temperature cycle experiments. Two complementary techniques, QCM-D and ellipsometry, were utilized simultaneously to probe the same substrate immersed in polymer solution. The interfacial processes were correlated with changes in polymer aggregation and viscosity of polymer solutions, as monitored by light scattering and rheological measurements. The simultaneous use of ellipsometry and QCM-D, and the possibility to follow layer properties up to 80 °C, well above the T(2) temperature, are both novel developments. A moderate increase in adsorbed amount with temperature was found below T(2), whereas a significant increase in the adsorbed mass and changes in layer properties were observed around the T(2) temperature where the bulk viscosity increases significantly. Thus, there is a clear correlation between transition temperatures in the adsorbed layer and in bulk solution, and we discuss this in relation to a newly proposed model that considers competition between aggregation and adsorption/deposition. A much larger temperature response above the T(2) temperature was found for adsorbed layers of HPMC than for layers of methyl cellulose. Possible reasons for this are discussed.     

含亚甲基和双二氮杂萘酮结构的聚芳酮的合成与性能

聚芳醚酮是一类重要的具有优异综合性能的工程塑料 ,它具有高的热稳定性、尺寸稳定性、耐溶剂性、好的加工性能和电性能 ,因而它经常作为复合材料的基质、粘合剂等被广泛的应用于航空、航天和电子等领域 .近几十年来 ,人们付出了很大的努力去开发聚芳醚酮新品种[1,2 ] .本研究组以 4 (4′ 羟基苯氧基 ) 2 ,3 二氮杂萘 1 (2Ｈ) 酮为缩聚单体制备了一系列的性能优良的聚芳醚酮[3～ 6] ,在主链中引入高密度的氮杂萘酮结构是获得高热稳定性和良好溶解性的重要途径 .由单体中含有更多的氮杂萘酮结构获得可溶解且耐温等级更高的聚芳酮是人们期…     

Lattice cluster theory of associating polymers. IV. Phase behavior of telechelic polymer solutions

The newly developed lattice cluster theory (in Paper I) for the thermodynamics of solutions of telechelic polymers is used to examine the phase behavior of these complex fluids when effective polymer-solvent interactions are unfavorable. The telechelics are modeled as linear, fully flexible, polymer chains with mono-functional stickers at the two chain ends, and these chains are assumed to self-assemble upon cooling. Phase separation is generated through the interplay of self-assembly and polymer/solvent interactions that leads to an upper critical solution temperature phase separation. The variations of the boundaries for phase stability and the critical temperature and composition are analyzed in detail as functions of the number M of united atom groups in a telechelic chain and the microscopic nearest neighbor interaction energy ε(s) driving the self-assembly. The coupling between self-assembly and unfavorable polymer/solvent interactions produces a wide variety of nontrivial patterns of phase behavior, including an enhancement of miscibility accompanying the increase of the molar mass of the telechelics under certain circumstances. Special attention is devoted to understanding this unusual trend in miscibility.     

Aggregation behavior of polypropylene oxide with electric charges at both ends in aqueous solution

The aggregation behavior of polypropylene oxide (PPO) with positive charges at both ends was investigated in aqueous solution by means of the measurements of solution turbidity, dynamic light-scattering, differential scanning calorimetry, and dye solubilization. The positive charges were produced by protonation of terminal NH(2) groups attached to the polymer composed of 33 PO units. It was found that the aggregation behavior is quite sensitive to temperature. At low temperature, the polymer dissolves in water as a unimer. When temperature is increased, the unimer solution undergoes a phase separation to give a turbid solution. Further increase in temperature produces a transparent micellar solution. The aggregation of the polymer molecules must be induced by the dehydration of PPO chain caused by temperature increase. According to the analysis of heat absorptions associated with the melting of the solid mixture and the phase separation of the unimer solution, it is suggested that approximately 10% dehydration of PPO chain causes the phase separation. The temperature-composition phase diagram of aqueous mixture of this polymer was constructed on the basis of turbidity and DSC experiments, which reveals the aggregation behavior of this polymer in aqueous medium as a function of concentration and temperature.     

Interpenetration of polystyrene chains in bulk polymer

Polystyrenes lightly substituted with either tertiary amine groups or nitrophenol groups have been allowed to interact in concentrated t-butylbenzene solution and in bulk polymer. Above the glass transition temperature a temperature dependent equilibrium is achieved in the bulk polymer between the two substituents and the amine salt of the phenol. The degree of association found is considerably greater in the bulk polymer than in solution. The results show that much interpenetration of the polymer occurs, and the results are discussed in terms of models of the bulk amorphous state of the polymer.