Investigation of structure–spectroscopy–function relationship of two-dimensional J-aggregates of tetrachlorobenzimidazolocarbocyanine preferentially oriented in poly-vinyl-alcohol thin films

The structure–spectroscopy–function relationship of 1,1′,3,3′-tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine (TTBC) aggregates is studied using a combination of experimental and theoretical techniques. The aggregates are macroscopically aligned in poly-vinyl-alcohol thin films by vertical spin coating. Angular dependence of the UV–Vis spectra is measured at eleven different orientations between the electric field polarization and the macroscopic alignment axis. The aggregates are characterized by a pair of Davydov split bands with opposite polarization behaviors: an H-band (505 nm) and a J-band (594 nm) polarized respectively, close to being parallel and perpendicular to the alignment axis. Spectral response is interpreted via simulations within the Frenkel exciton formalism. TTBC aggregates are shown to assume very similar internal molecular packing (herringbone) and dynamics of excited states (phonon-assisted intraband and interband relaxations) in ionic aqueous solution and in thin films. The general conclusions on the structure–spectroscopy–function relationship are expected to hold for other cyanine aggregates with the same generic spectral features.     

Synthesis of photoactive single‐chain folded polymeric nanoparticles via combination of radical polymerization techniques and Menschutkin click chemistry

This contribution reports that synthesis of polystyrene based photoactive polymeric nanoparticles by radical copolymerization and Menschutkin Chemistry methodology. In the first step, poly(styrene‐co‐chloromethyl styrene) was achieved by thermally initiated radical copolymerizations and subsequently copolymers were reacted to commercially available Type II photoiniator (Michler's ketone) in dilute condition in order to achieve intramolecular crosslinked polymeric nanoparticles. After the characterization studies, polymeric nanoparticles were used for free radical photopolymerization of methacrylic formulations to determine the initiation efficiency. Upon UV irradiation, resulting polymeric nanoparticle lost its globular structure by releasing benzophenone part and transformed into linear copolymer analogue. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1998–2003     

Poly(ethylene glycol)‐thioxanthone prepared by Diels–Alder click chemistry as one‐component polymeric photoinitiator for aqueous free‐radical polymerization

Novel water‐borne macrophotoinitiator containing thioxanthone (TX) end group was successfully synthesized by using Diels–Alder (DA) [4 + 2] click chemistry strategy. For this purpose, thioxanthone‐anthracene (TX‐A) and maleimide end‐functionalized poly(ethylene glycol) (PEG‐MI) were reacted in toluene at reflux temperature for 48 h. The final polymer (PEG‐TX) and the intermediates were characterized in detail by spectral analysis. PEG‐TX possesses absorption characteristics similar to the parent TX. The one‐component photoinitiating nature of the photointiator was demonstrated by photopolymeization of several hydrophilic vinyl monomers, such as acrylic acid, acrylamide, 2‐hydroxyethyl acrylate, and 1‐vinyl‐2‐pyrrolidone. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2109–2114, 2010     

Preparation of hydrogels by photopolymerization of acrylates in the presence of Type I and one-component Type II photoinitiators

Hydrogels were prepared by photoinduced polymerization of poly(ethylene glycol)monoacrylate (PEGMA) and poly(ethylene glycol)diacrylate (n = 200 and 700) (PEGDA) with Type I, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one (I-2959) and one-component Type II initiators: (9-oxo-9H-thioxanthen-2-yloxy)-acetic acid (TXOCH₂COOH) and (9-oxo-9H-thioxanthen-2-yloxy)-sodium acetate (TXOCH₂COO^?Na⁺). The swelling properties of hydrogels were investigated and observed to be excellent. Smooth morphology and no phase separation were observed from SEM micrographs of the hydrogels.     

Adaptive Pull�CPush Based Event Tracking in Wireless Sensor Actor Networks

Wireless sensor networks have attracted significant interest for various scientific, military, and e-health applications. Recently a new class of sensor networks ??sensor/actor networks?? has been introducing new research challenges due to the unique coordination requirements among sensors and actors. In sensor/actor networks, actors are the nodes that have the capability to move in the field, equipped with powerful devices and can respond to the events of interest. With this capability, autonomous operation of the network is possible without a centralized controlling mechanism. This, however, requires the network to apply cooperative mechanism to decide when and how monitoring is done to track the event and how the event will be responded. In this regard, little work has been done in terms of co-existing Push and Pull data flows in the network. In this paper, we propose an Adaptive Pull?CPush (APP) based Event Tracking approach that allows sensor-to-actor communication as well as actors coordination in response to the events occurred. APP proposes two models of sensors organization: region-based organization (RAPP) and neighbor-based organization (NAPP) to alert nodes in the vicinity of reported event. APP exploits the mobility of actor nodes to form dynamic responsibility clusters, thus ensuring an event specific response to emergencies. Routing in APP is based on Routing by Adaptive Targeting (RAT), which is a delay-constrained geographical routing protocol. Simulation results reveal significant performance improvement in terms of response time and energy conservation.     

Synthesis,characterization, and biological evaluation of new copper complexes of naphthyl pyrazole ligands

Two naphthalene pyrazole ligands were synthesized using KOH/DMSO and Cu catalyst and characterized with FT-IR, ESI-MS, ¹H, and ¹³C NMR spectroscopies. The crystal structures of 1-(2-methylnaphthalen-1-yl)-1H-pyrazole (MeNap-Pz) ligand have been determined with X-ray crystal structure analysis. Reaction of the ligands with Cu(NO₃)₂x3.5H₂O gave two new complexes and characterized with magnetic susceptibility, molar conductance, FT-IR, LCMS-MS, ICP-OES, NMR, thermogravimetric analysis, and ESR spectra. The spectral data of the ligands are coordinated to the metal ion through the nitrogen atoms of the pyrazole ring. Consequently, it has been determined that [Cu(MeNap-Pz)₂(NO₃)]NO₃.2H₂O complex showed square planar geometry and [Cu(NapMe-Pz)₂(NO₃)₂].H₂O complex showed octahedral geometry. All compounds were screened for in vitro antibacterial activity and copper complexes have been shown to be effective on bacteria.     

Absorption spectrum of monomeric pseudoisocyanine: A new perspective and its implications for formation and spectral response of J-aggregates in solution and in thin films

We argued against the current spectral assignment for absorption spectrum of monomeric PIC which is widely accepted since the pioneering works of Scheibe and Jelley [G. Scheibe, Angew. Chem. 49 (1936) 563; E.E. Jelly, Nature 138 (1936) 1009]. A new spectrum is presented along with its conceptual basis. The hypothesized spectrum attributes the previous 0–0 (≈525 nm) and 0–1 (≈490 nm) assignments, respectively, to intermediates acting as the precursor of J-aggregates and to the 0–0 transition of monomeric PIC and brings the spectrum in accord with the seemingly universal spectral fingerprint of cyanines. The hypothesis is used to analyze and interpret the temperature dependence of the UV–vis absorption of PIC aggregates in saline aqueous solution by incorporating the J-band simulations within frenkel exciton formalism. Its implications for aggregate formation kinetics are given on the basis of current spectroscopic evidence. The hypothesis readily answers several long-standing questions: Why compared to many other cyanines at least an order of magnitude higher dye concentration is needed to form J-aggregates of PIC? Why are there no precursors, since aggregation is expected to be a consecutive process? A large number of observations on steady-state and time-resolved spectral properties, and aggregation kinetics in solution/thin films are likely to find reasonable explanations within this hypothesis.     

A novel method for the production of conductive ring spun yarn

To take the advantages of spun yarns such as porosity, softness, bending as well as usability as yarn/fabric forms, this study worked on an alternative conductive yarn production method. Different from widely used application methods, a conductive nanosuspension was applied to viscose, cotton and polyester open fibre bundles with different feeding amounts during the ring spinning with a specially developed apparatus. Reduced graphene oxide (rGO) synthesized with a single step process instead of two-step processes was used to impart conductivity. Following to yarn production, winding, knitting and washing processes were realized to evaluate the changes in yarn conductivity and the usability of the yarns in the post-spinning processes. In addition to tensile properties of the yarns and air permeability of the fabrics, electrical resistance and environmental impact of the method was compared with immersion and drying process. The results indicated that alternative method allows the production of conductive (lower resistance than 100 kΩ) but also strong, flexible, washable and breathable electronic textile products with an environmentally friendly process. There has been no effort, as yet, to get conductivity in this manner. Therefore, the developed method can be considered to be a new application in the functional yarn production field. The produced conductive yarns can be converted into fabric form by weaving, knitting and embroidery. Therefore, they can also be seen as an ideal as the platforms for future wearable electronics.

     

Reentrant phase transition and network parameters of hydrophobically modified poly[2-(diethylamino)ethylmethacrylate-co-N-vinyl-2-pyrrolidone/octadecyl acrylate] hydrogels

Hydrophobically modified poly[2-(diethylamino)ethylmethacrylate-co-N-vinyl-2-pyrrolidone/octadecyl acrylate] [P(DEAEMA-NVP/OA)] hydrogels with different OA content were prepared by free-radical crosslinking copolymerization of corresponding monomers in tert-butanol. The swelling equilibrium of the hydrogels was investigated as a function of temperature and hydrophobic comonomer content in pure water. An interesting feature of the swelling behavior of the P(DEAEMA-NVP/OA) hydrogels was the reentrant phase transition where the hydrogels collapse once and reswell as temperature increased. The average molecular mass between crosslinks and polymer-solvent interaction parameter (χ) of the hydrogels were calculated from equilibrium swelling values. The enthalpy (ΔH) and entropy (ΔS) changes appearing in the χ parameter for the hydrogels were determined by using the Flory-Rehner theory. It was observed that the experimental swelling data of the hydrophobic hydrogels at different temperature agreed with the Flory-Rehner theory, that provided that the sensitive dependence of χ parameter on both temperature and polymer concentration is taken into account.     

A study of the surface analysis of some water‐soluble polymers by inverse gas chromatography

The surface characterization of 2‐(dimethylamino)ethylmethacrylate (DMA) and 2‐(N‐morpholino)ethylmethacrylate (MEMA) homopolymers and DMA–MEMA diblock copolymer was studied using inverse‐gas chromatography (IGC). The analyzed surface properties of (co)polymers were the dispersive component of the surface energy ( ) and the acid–base characters of (co)polymer surfaces. The specific free energy (ΔG^sp), enthalpy (ΔH^sp), and entropy (ΔS^sp) of adsorption of polar probes on (co)polymers were calculated. The values of ΔH^sp were correlated with both the donor and the modified acceptor numbers (AN) of the probes to quantify the acidic K_A and the basic K_D parameters of (co)polymer surfaces. The values obtained for the K_A and K_D parameters indicated basic characters for the surface of (co)polymers. The dispersive component values of the surface energy and the acid–base surface parameters of the DMA–MEMA diblock copolymer surface were found to be between those homopolymers as expected. Copyright © 2008 John Wiley & Sons, Ltd.