A comparative study on the structural changes in leucoemeraldine and emeraldine base upon doping by perchlorate

The changes in the structure of leucoemeraldine (LM) and emeraldine (EM) base upon doping by perchlorate anions are studied by X-ray photoelectron spectroscopy (XPS) and infrared (IR) absorption spectroscopy. In the case of LM, interactions of the amine nitrogens with the perchlorate anions result in a nitrogenonium ion structure analogous to that arising from the protonation of imine nitrogens in EM by HCl except the chloride anion in the latter has been replaced by the perchlorate anion. A small amount of partially ionic and covalent chlorine is also incorporated in the LM–perchlorate complexes. The maximum electrical conductivity that is achieved in these complexes is about 4 S/cm. In contrast, the maximum conductivity of the EM–perchlorate complexes is three orders of magnitude lower. The interactions of perchlorate anions with EM base result in the preferential disappearance of the imine units over the amine units.     

Controlled grafting of well-defined epoxide polymers on hydrogen-terminated silicon substrates by surface-initiated ATRP at ambient temperature

Controlled grafting of well-defined epoxide polymer brushes on the hydrogen-terminated Si(100) substrates (Si-H substrates) was carried out via the surface-initiated atom-transfer radical polymerization (ATRP) at room temperature. Thus, glycidyl methacrylate (GMA) polymer brushes were prepared by ATRP from the alpha-bromoester functionalized Si-H surface. Kinetic studies revealed a linear increase in GMA polymer (PGMA) film thickness with reaction time, indicating that chain growth from the surface was a controlled "living" process. The graft polymerization proceeded more rapidly in the dimethylformamide/water (DMF/H(2)O) mixed solvent medium than in DMF, leading to much thicker PGMA growth on the silicon surface in the former medium. The chemical composition of the GMA graft-polymerized silicon (Si-g-PGMA) surfaces were characterized by X-ray photoelectron spectroscopy (XPS). The fact that the epoxide functional groups of the grafted PGMA were preserved quantitatively was revealed in the reaction with ethylenediamine. The "living" character of the PGMA chain end was further ascertained by the subsequent growth of a poly(pentafluorostyrene) (PFS) block from the Si-g-PGMA surface, using the PGMA brushes as the macroinitiators.     

Electrofiltration of Aqueous Suspensions

Electrofiltration of hydrosols in fixed-bed filters was studied experimentally. The experimental variables examined included media type, electric field strength, and suspension pH values. The extent of particle removal was found to improve with the application of the electric field, and lower pH values favor particle collection. The filtrate quality displayed the transient behavior of increasing particle concentration with time. A simple model which assumes that the filter coefficient decreases linearly with the extent of deposition was developed and found capable of predicting the observed behavior. Copyright 2000 Academic Press.     

Organic/inorganic hybrid nanospheres coated with palladium/P4VP shells from surface‐initiated atom transfer radical polymerization

Crosslinked poly(4‐vinylbenzyl chloride) (PVBC) nanospheres of about 160 nm were first synthesized by emulsion copolymerization of 4‐vinylbenzyl chloride (VBC) in the presence of a crosslinking agent, p‐divinylbenzene. Subsequent modification of the nanosphere surfaces via surface‐initiated atom transfer radical polymerization of 4‐vinylpyridine, using the VBC units of PVBC on the nanosphere surface as the macroinitiators, produced a well‐defined and covalently tethered poly(4‐vinylpyridine) (P4VP) shells of 24–27 nm in thickness. Activation of the P4VP shells in a PdCl₂ solution, followed by reactions with CO or H₂S gas, gave rise to the corresponding P4VP composite shells containing densely dispersed palladium metal or palladium sulfide nanoparticles. The chemical composition of the nanosphere surfaces at various stages of surface modification was characterized by X‐ray photoelectron spectroscopy. Field emission scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of the organic/inorganic hybrid nanospheres coated with palladium/P4VP shells. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2119–2131, 2008     

Biomimetic anchors for antifouling and antibacterial polymer brushes on stainless steel

Barnacle cement (BC) was beneficially applied on stainless steel (SS) to serve as the initiator anchor for surface-initiated polymerization. The amine and hydroxyl moieties of barnacle cement reacted with 2-bromoisobutyryl bromide to provide the alkyl halide initiator for the surface-initiated atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA). The hydroxyl groups of HEMA polymer (PHEMA) were then converted to carboxyl groups for coupling of chitosan (CS) to impart the SS surface with both antifouling and antibacterial properties. The surface-functionalized SS reduced bovine serum albumin adsorption, bacterial adhesion, and exhibited antibacterial efficacy against Escherichia coli (E. coli). The effectiveness of barnacle cement as an initiator anchor was compared to that of dopamine, a marine mussel inspired biomimetic anchor previously used in surface-initiated polymerization. The results indicate that the barnacle cement is a stable and effective anchor for functional surface coatings and polymer brushes.     

Bistable electrical switching and memory effects in a thin film of copolymer containing electron donor-acceptor moieties and europium complexes

A nonconjugated methacrylate copolymer (PCzOxEu) containing carbazole moieties (electron donors), 1,3,4-oxadiazole moieties (electron acceptors), and europium complexes in the pendant groups was synthesized via free radical copolymerization of methacrylate monomers containing the respective functional groups. The molecular structure and composition of PCzOxEu was characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR, UV-vis absorption and fluorescence spectroscopies, gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CyV). The resulting copolymer exhibited a relatively high glass transition temperature (Tg approximately 125 degrees C) and good solubility in common organic solvents. It could be cast into transparent films from solutions. For a thin film of PCzOxEu sandwiched between an indium-tin oxide (ITO) electrode and an Al electrode (ITO/PCzOxEu/Al), the structure behaved as a nonvolatile flash (rewritable) memory with accessible electronic states that could be written, read, and erased. The polymer memory exhibited an ON/OFF current ratio up to 10(5), switching response time of approximately 1.5 micros, more than 10(6) read cycles, retention time of more than 8 h, and write/erase voltages of about 4.4 V/-2.8 V under ambient conditions. The roles of oxadiazole moieties in improving the response time and retention time of the memory device were elucidated from the molecular simulation results.     

Preparation of well-defined polymer-silicon wafer hybrids via surface-initiated RAFT-mediated process

A simple method was developed for the immobilization of reversible addition-fragmentation chain-transfer (RAFT) initiators on the silicon surface. Well-defined polymer-silicon hybrids, including the tethered brushes of glycidyl methacrylate (GMA) polymer, poly(ethylene glycol) monomethacrylate (PEGMA) polymer and block copolymer on a silicon wafer, were prepared via surface-initiated RAFT living radical polymerization. The “living” chain ends were used as the macroinitiator for the subsequent synthesis of diblock copolymers.     

Electroless deposition of copper on polyimide films modified by surface graft copolymerization with nitrogen-containing vinyl monomers

Surface modification of Ar-plasma-pretreated polyimide (PI) films (Kapton® HN films) via UV-induced graft copolymerization with 1-vinylimidazole (VIDz), 4-vinylpyridine (4VP), and 2-vinylpyridine (2VP) under atmospheric conditions was carried out to improve their adhesion with the electrolessly deposited Cu. The surface compositions of the graft-copolymerized PI films were characterized by X-ray photoelectron spectroscopy. The adhesion strength of the electrolessly deposited Cu on the surface-graft-copolymerized PI film was affected by the type of monomers used for graft copolymerization and the graft concentration. T-peel adhesion strengths of about 15, 10, and 6?N/cm were obtained for the Cu/graft-modified PI assemblies involving, respectively, the VIDz, 4VP, and 2VP graft-copolymerized PI films. These adhesion strengths are much higher than those obtained for assemblies involving electrolessly deposited Cu on pristine or on Ar-plasma-treated PI films. The adhesion strengths involving the VIDz and 4VP surface-graft-copolymerized PI films are also higher than those involving PI films modified by chemical etching. The cohesive failure inside the PI substrate of the Cu/graft-modified PI assemblies during delamination suggested that not only were the grafted polymer chains covalently tethered on the PI film, they were also incorporated into the metal matrix during the electroless plating process.     

Brush-type amphiphilic diblock copolymers from "living"/controlled radical polymerizations and their aggregation behavior

Two brush-type amphiphilic diblock copolymers, poly(poly(ethylene glycol)methyl ether methacrylate-block-polystyrene) (P(PEGMA)-b-PS) and poly(glycidyl methacrylate)-block-poly(poly(ethylene glycol)methyl ether methacrylate) (P(GMA)-b-P(PEGMA)) were synthesized, respectively, via consecutive atom-transfer radical polymerizations (ATRPs) and reversible addition-fragmentation chain-transfer (RAFT) polymerizations. The diblock copolymers were characterized by gel permeation chromatography (GPC), (1)H nuclear magnetic resonance (NMR) spectroscopy, and FT-IR spectroscopy. The aggregation behavior of the two amphiphilic diblock copolymers in water was also studied. Scanning electron and transmission electron microscopic images revealed that spherical micelles (40-80 nm in diameter) from self-assembly of the P(PEGMA)-b-PS copolymers and wormlike micelles (60-120 nm in length and 20-30 nm in diameter) from self-assembly of the P(GMA)-b-P(PEGMA) copolymers were prevalent. The spherical P(PEGMA)-b-PS micelles could self-assemble gradually into giant aggregates of several micrometers in diameter.     

Enhanced effect of RM-β-cyclodextrin on biodegradation of toluene in wastewater by activated sludge

Recently, air and ground water pollution and contamination of soil by toluene have been drawing increasing attention and became an urgently important problem in environmental pollution. Hence, the development of highly sophisticated removal techniques of toluene is required for the global environmental preservation. Since toluene is a highly volatile material, it is difficult to treat it by usual activated sludge water treatment. In this study, in order to prevent volatilization of toluene, randomly methylated β-cyclodextrin (RM-β-CD) was used to complex with toluene and by reason of that, facilitates the biodegradation of toluene by activated sludge. The enhanced effect of RM-β-CD for the biodegradation of toluene by activated sludge was studied in batch systems. The addition of RM-β-CD dominantly promoted proliferation of activated sludge. This implied that the addition of RM-β-CD prevented toluene from evaporating during treatment, and as a result, toluene was effectively decomposed by the activated sludge.