Search

Solvent-free chemical oxidative polymerizations of pyrrole and its derivatives, namely

Responsive liquid marbles (LMs), which can change their shape, stability, and motion by the application of stimuli, attract a growing interest due to their wide range of applications. Our approach to design photo- and thermoresponsive LMs is based on the use of micrometer-sized fatty acid (FA) particles as phase change material covered with polypyrrole (PPy) overlayers with photothermal property. The core-shell particles were synthesized by aqueous chemical oxidative seeded dispersion polymerization. First, we investigated the effect of the alkyl chain length of FA on the resulting FA/PPy core-shell particles by characterizing their size and its distribution, shape, morphology, chemical composition, and photothermal behavior. Then LMs were fabricated by rolling water droplets on the dried FA/PPy particle powder bed and their light and temperature dual stimuli-responsive nature was studied as a function of the FA alkyl chain length. For all FAs studied, LMs disrupted in a domino manner by light irradiation as the first trigger: the temperature of the FA/PPy particles on the LM surface increased by light irradiation, followed by phase change of FA core of the particles from solid to liquid, resulting in disruption of the LM and release of the encapsulated water. The disruption time was closely correlated to the melting point of FA linked to the alkyl chain length and light irradiation power, and it could be controlled and tuned easily between quasi instantaneous and approximately 10 s. Finally, we showed potential applications of the LMs as a carrier for controlled delivery and release of substances and a sensor.

The long-term morphological and chemical stabilities of polypyrrole grains in aqueous media (1-year duration) are investigated. Polypyrrole grains doped with chloride ions or heptadecafluorooctane sulfonic acid were extensively characterized using a wide range of analytical techniques. The average sizes of the grains were 13–15 μm and consisted of submicrometer-sized atypical primary particles. The grain size increased in the case of polypyrrole doped with chloride ions, whereas no apparent changes were observed in the case of polypyrrole doped with heptadecafluorooctane sulfonic acid after storage at pH 3 and 10. The size and morphology of the primary particles did not change for each grain system. Appreciable changes in chemical structure and surface chemistry were observed. At pH 10, dedoping occurred easily, and chloride ions and heptadecafluorooctane sulfonic acid were released from the grains in a short time (within one week). On the other hand, the dopants were released slowly at pH 3, which is likely caused by nucleophilic attack by water molecules to the polypyrrole. The release rate of the dopant was slower for polypyrrole doped with heptadecafluorooctane sulfonic acid than for polypyrrole doped with chloride ions. This finding is attributed due to the stronger hydrophobic interaction between polypyrrole and heptadecafluorooctane sulfonic acid. Long-term morphological and chemical stabilities of polypyrrole grains doped with chloride ion or heptadecafluorooctane sulfonic acid in aqueous media (1-year duration) are studied. There were appreciable changes in chemical structure and surface chemistry, although the size and morphology of the polypyrrole primary particles did not change for each grain system. The dopants were released with time, and its rate was slower for the polypyrrole doped with heptadecafluorooctane sulfonic acid, compared to that doped with chloride ion. This should be due to the stronger hydrophobic interaction between polypyrrole and heptadecafluorooctane sulfonic acid.

Polystyrene particle-stabilized Pickering-type paraffin droplets were successfully coated by polypyrrole overlayers by aqueous chemical oxidative polymerization of pyrrole, and the thickness of polypyrrole overlayer could be controlled simply by changing pyrrole concentration in the polymerization media. Remote motion control of the droplets was realized on a planar air–water surface by site-selective near-infrared light irradiation, due to light-to-heat photothermal property of the polypyrrole. Furthermore, motion control of the paraffin droplet was also possible using sunlight focused using a magnifying glass. A Marangoni flow induced by site-selective light irradiation of the droplet could work as a driving force to move the droplet on the air–water surface, and the direction and timing of irradiation could control those of the motion on demand. Path length, velocity, and decay time of the droplet motions became longer and larger with an increase of thickness of polypyrrole overlayer, which was confirmed by numerical analyses.

Phototaxis, which is the directional motion toward or away from light, is common in nature and inspires development of artificial light-steered active objects. Most of the light-steered objects developed so far exhibit either positive or negative phototaxis, and there are few examples of research on objects that exhibit both positive and negative phototaxis. Herein, small objects showing both positive and negative phototaxis on the water surface upon near-infrared (NIR) light irradiation, with the direction controlled by the position of light irradiation, are reported. The millimeter-sized tetrahedral liquid marble containing gelled water coated by one polymer plate with light-to-heat photothermal characteristic, which adsorbs onto the bottom of the liquid marble, and three polymer plates with highly transparent characteristic, which adsorb onto the upper part of the liquid marble, is utilized as a model small object. Light irradiation on the front side of the object induces negative phototaxis and that on the other side induces positive phototaxis, and the motion can be controlled to 360° arbitrary direction by precise control of the light irradiation position. Thermographic studies confirm that the motions are realized through Marangoni flow generated around the liquid marble, which is induced by position-selective NIR light irradiation. The object can move centimeter distances, and numerical analysis indicates that average velocity and acceleration are approximately 12 mm/s and 71 mm/s2, respectively, which are independent of the direction of motions. The generated force is estimated to be approximately 0.4 μN based on Newton's equation. Furthermore, functional cargo can be loaded into the inner phase of the small objects, which can be delivered and released on demand and endows them with environmental sensing ability.

Liquid marble (LM) can be prepared by the adsorption of hydrophobic powder on the gas–liquid interface of a water droplet. Generally, LM is prepared using hydrophobic powder with a size of >100 nm....

Hairy particles consisting of polyisoprene-b-polystyrene (PI-b-PS) were synthesized by polymerization-induced self-assembly (PISA) based on a living anionic polymerization method. The molecular agg...

There has been increasing interest in colloidal particles adsorbed at the air-water interface, which lead to stabilization of aqueous foams and liquid marbles. The wettability of the particles at the interface is known to play an important role in determining the type of air/water dispersed system. Foams are preferably formed using relatively hydrophilic particles, and liquid marbles tend to be formed using relatively hydrophobic particles. In this study, submicrometer-sized polystyrene particles carrying poly(

A strategy to obtain chiral silica using an achiral stereoregular polymer with polyhedral oligomeric silsesquioxane (POSS) side chains is described herein. The preferred helical conformation of the POSS-containing polymer could be achieved by mixing isotactic polymethacrylate-functionalized POSS (it-PMAPOSS) and a chiral dopant. The array structure of POSS molecules, which are placed along the helical conformation, is memorized even after removing the chiral dopant at high temperatures, leading to a chiral silica compound with exclusive optical activity after calcination.

Background: Early detection of cerebral infarction (CI) by home acupuncturists might be helpful in reducing stroke mortality. We compared vital signs of patients who developed CI and those who did not to ascertain if blood pressure balance is a useful marker for the early detection of CI and for distinguishing cases with potentially effective/ineffective acupuncture treatment. Methods: In this retrospective study, vital signs such as body temperature, pulse, and blood pressure, were simultaneously obtained from the right and left arms of patients who received weekly acupuncture treatment. We focused on the differences between values obtained from the right and left arms (the balance) and compared the values of patients who developed CI [CI (+)] (n = 18) and those of age-/gender-matched patients who did not [CI (−)] (n = 18). Results: Left/right blood pressure was significantly more unbalanced in the CI (+) group than in the CI (−) group, especially immediately before the onset of CI. Moreover, all CIs occurred on the side with a lower blood pressure. Discussion and Conclusions: Blood pressure balance might aid in the early detection of CI and to determine whether treatment with traditional or modern medicine is more appropriate. Acupuncture may thus help maintain patients’ quality of life.

Millimeter-sized polystyrene particles coated with a hydrophobic polypyrrole overlayer were successfully synthesized by aqueous chemical oxidative seeded polymerization. The dried particles could e...

An anaerobic baffled reactor (ABR) is one of the useful wastewater treatment technologies, but the knowledge about its treatment performance for actual wastewater with load fluctuation is limited. The organic removal performance of an ABR for treating supermarket wastewater was evaluated. The ABR, which consisted of eight columns, was examined under four hydraulic retention time (HRT) conditions of 19.4, 12.9, 8.0, and 4.4 h. As a result, the unfiltered chemical oxygen demand (COD) removal efficiency was 80 (±8) % at an HRT of 19.4 h. When the HRT was shortened to 12.9 h, the average unfiltered COD removal efficiency decreased to 58 (±15) %. However, it showed buffering effect against high load inflow in the first column, indicating that it is useful as a pretreatment system under this condition. At an HRT of 4.4 h, the unfiltered COD removal efficiency decreased to 9%, indicating the system failed. The results of the microbial community structure analysis showed that the detection frequency of acidogenic bacteria decreased in proportion to the extension of residence time in the reactor. These results indicate that the ABR is useful for the treatment of supermarket wastewater with load fluctuations as a main treatment system at a HRT of 19.4 h and as a pretreatment system at a HRT of 12.9 h.

To improve the toughness of epoxy polymers, cross-linked rubber (CLR) particles or core–shell rubber (CSR) particles can be blended into the epoxy matrix. Particle cavitation is thought to be the main toughening mechanism of rubber-modified epoxies. Although CLR-modified epoxies have not been studied in depth previously, it is expected that the toughening mechanism differs from that of CSR-modified epoxies because void formation is less likely to occur. We formed the CLR- and CSR-modified epoxy resins using nanosized acrylonitrile butadiene CLR particles, which showed good compatibility with the epoxy matrix and the CSR particles with a rubbery core surrounded by a glassy shell. The toughening mechanism was examined by comparing the fracture behavior, fracture surfaces, and process zones via tensile and fracture toughness testing, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and transmission optical microscopy (TOM). There was a difference in the characteristics of the R-curves between the CLR- and CSR-modified epoxies. In addition, the SEM and TEM observations indicated that there was a difference in the fracture mechanism.

The deterioration mechanisms of chip resistors with both multilayered Au/Ni/Ag electrodes and glass-covered coatings were studied at temperatures above 250 °C, the possible driving temperature of f...

Liquid marbles are water droplets coated with solid particles that prevent coalescence and allow storage, transport, and handling of liquids in the form of a powder. Here, we report on the formation of liquid marbles that are stabilized entirely by a single monolayer of solid particles and thus minimize the amount of required solid material. As stabilizing particles, we synthesize relatively monodisperse, 80 μm-sized polystyrene (PS) particles coated with heptadecafluorooctanesulfonic acid-doped polypyrrole (PPy-C

Polypyrrole, poly(N-methyl pyrrole) and poly(N-ethyl pyrrole) grains were synthesized by aqueous chemical oxidative polymerization in the presence of sodium dodecyl sulfate as both a dopant and a hydrophobizing agent. The resulting grain products were characterized in terms of their size, morphology, surface and bulk chemical compositions, hydrophilic–hydrophobic balance, (photo)thermal property, and conductivity. Scanning electron microscopy studies indicated that the grains were aggregates of atypical particles with submicrometer size. Elemental microanalysis and thermogravimetric analysis confirmed the production of dodecyl sulfate-doped polypyrrole, poly(N-methyl pyrrole) and poly(N-ethyl pyrrole) materials, and they showed near-infrared light-to-heat photothermal properties, which was confirmed by thermography. The data obtained through X-ray photoelectron spectroscopy indicated the presence of dodecyl sulfate dopants on the surface of the grains. The dried polypyrrole and poly(N-ethyl pyrrole) grains showed hydrophobic character, and therefore, they can adsorb to the air–water interface and act as a light-responsive liquid marble stabilizer. Locomotion of the liquid marble can be driven by near-infrared laser irradiation-induced Marangoni flow on a planar air–water surface. The release of internal liquid can be achieved by controlled disruption of liquid marbles via external stimulus application. Polypyrrole and poly(N-alkyl pyrrole) grains were synthesized by aqueous chemical oxidative polymerization in the presence of sodium dodecyl sulfate as both a dopant and a hydrophobizing agent. The dried polypyrrole and poly(N-ethyl pyrrole) grains showed hydrophobic character and can act as a light-responsive liquid marble stabilizer. Locomotion of the liquid marble can be driven by near-infrared laser irradiation-induced Marangoni flow on a planar air–water surface. Furthermore, the release of internal liquid can be achieved by controlled disruption of liquid marbles via external stimulus application.

Remotely controlling the movement of small objects is a challenging research topic, which can realize the transportation of materials. In this study, remote locomotion control of particle-stabilized bubbles on a planar water surface by near-infrared laser or sunlight irradiation is demonstrated. A light-induced Marangoni flow was utilized to induce the locomotion of the bubbles on water surface, and the timing and direction of the locomotion can be controlled by irradiation timing and direction on demand. The velocity, acceleration, and force of the bubbles were analyzed. It was also confirmed that the bubbles can work as light-driven towing engines to pull other objects. Furthermore, it was demonstrated that the bubbles can work as an adhesive to bond two solid substrates by application of compressive stress under water. Such remote transport of the materials, pulling of the objects by light, and controlling the release of gas on demand should open up a wide field of conceivable applications.

Liquid marbles were prepared using a water droplet and nonprotonated hydrophobic poly(2-N,N-diisopropylaminoethyl methacrylate) (PDiPAEMA) powder. Although the nonprotonated PDiPAEMA was hydrophobic, PDiPAEMA became hydrophilic because of the protonation of the pendant tertiary amino groups under acidic conditions. Therefore, liquid marbles stabilized with PDiPAEMA powder could float on a neutral to basic water surface, but they immediately disintegrated on an acidic water surface. Furthermore, the liquid marbles floating on the water surface disintegrated in response to CO2 gas because the water became acidic as a result of carbonic acid formation.