Synthesis and electro-optical properties of self-doped ionic conjugated polymers: poly[2-ethynyl-N-(4-sulfobutyl)pyridinium betaine]

A noble self-dopable conjugated polybetaine, poly[2-ethynyl-N-(4-sulfobutyl)pyridinium betaine] (PESPB) was synthesized by the activated polymerization of 2-ethynylpyridine with 1,4-butanesultone without any additional initiator or catalyst. This polymerization proceeded at the condition of high temperature (130 °C). The polymer yield and inherent viscosity were 82% and 0.13 dl/g, respectively. The chemical structure of PESPB was identified by various instrumental methods to have a conjugated ionic polymer bearing the sulfobetaine moieties. This poly(sulfobetaine) was found to be more soluble in salt solution than in salt-free solution. The photoluminescence peak is located at 530 nm corresponding to the photon energy of 2.34 eV. The photoluminescence intensity was increased as the temperature is increased. At 1 kHz and room temperature, the dielectric constant and electrical conductivity of PESPB were 5.7 and 3.5 × 10⁻⁹ S/cm, respectively.     

Synthesis and electro-optical properties of an ionic conjugated polymer: Poly[N-(6-azidohexyl)-2-ethynylpyridinium iodide]

An azide group-containing conjugated ionic polymer was synthesized by the direct polymerization of 2-ethynylpyridine and 6-azidohexyl iodide at 60 °C in methanol without any additional initiator or catalyst. This reaction proceeded well in homogeneous manner to give a moderate yield of the polymer (yield: 71%). The initial light-brown solution of 2-ethynylpyridine and 6-azidohexyl iodide became a viscous dark-red solution as the polymerization proceeded. The FT-IR spectrum of the polymer did not show the acetylenic CC bond stretching (2110 cm⁻¹) and acetylenic C–H bond stretching (3293 cm⁻¹) frequencies of 2-ethynylpyridine. This polymer was completely soluble in water, methanol, DMF, and DMSO, and the polymer was found to be mostly amorphous. The photoluminescence (PL) spectra of poly[N-(6-azidohexyl)-2-ethynylpyridinium iodide] showed that the photoluminescence peak is located at 596 nm, corresponding to a photon energy of 2.08 eV.     

Synthesis of block copolymers derived from N-trityl-(S)-serine and pyrene end-labeled poly(methyl methacrylate) or poly(N-isopropylacrylamide) via ATRP

A new monomer bearing N-trityl-l-serine methyl ester in structure, methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine (MTS), was prepared to be further polymerized by atom transfer radical polymerization (ATRP) with pyrene-endcapped poly(methyl methacrylate) (Py–PMMA–Br) or poly(N-isopropylacrylamide) (Py–PNIPA–Br). The resulting block copolymers, poly(methyl methacrylate–block–methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine) (Py–PMMA–b–PMTS) and poly(N-isopropylacrylamide–block–methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine (Py–PNIPA–b–PMTS) were characterized by ¹H (¹³C) NMR, ultraviolet, FTIR and fluorescence spectroscopy, thermal analysis, differential scanning calorimetry (DSC), atomic force microscopy (AFM), scanning electron microscopy (SEM), and gel permeation chromatography (GPC) measurements. The chemical composition in Py–PMMA–b–PMTS was estimated from the ¹H NMR analysis that indicated a ratio of the repeating units of 46:19 (MMA:MTS). For the Py–PNIPA–b–PMTS the composition rate in the copolymer was 61:25 (NIPA:MTS). Quenching of the pyrene species with N,N-diethylaniline, nitrobenzene, nitrophenol, potassium iodide, p-nitrotoluene and tetracyanoquinodimethane (TCNQ) in DMF solution excited at 348 nm was evidenced, more efficiently being nitrophenol and TCNQ. In this case, the monomer emission at 388–409 nm underwent a significant decrease caused of an electron transfer from the electron-reach photoexcited pyrene molecule to the electron-deficient quenchers.     

Electropolymerization and electrochemical properties of poly(N-(N-carbazolylalkyl)aniline)

We synthesized N-carbazolylalkyl (ethyl, propyl, butyl, hexyl) aniline which has carbazole and aniline functional group together. Poly(N-N-carbazolylalkyl)aniline) has been synthesized by electrochemical polymerization in an acetonitrile solution containing 1 M H₂SO₄ on the platinum electrode. Polymer film showed reversible process in redox reaction and typical oxidation of aniline group. Poly(N-N-carbazolylhexyl)aniline) (PNCHA) showed clearly two oxidation peaks at around 0.65 and 0.75 V during electropolymerization. The color of poly(N-N-carbazolylalkyl)aniline) changed from transparent light-green in reduction state to dark green in oxidation state.     

Poly(ethylene glycol)/poly(2-acrylamido-2-methyl-1-propane sulfonic acid) gel electrolytes: a detailed investigation of their conductivity and characterization

Poly(ethylene glycol)/poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PEG/PAMPS) with a transparent appearance were prepared in the presence of ammonium persulfate (APS) as an initiator at 70 °C for 24 h. PEG/PAMPS-based polymer gel electrolytes in a motionless and uniform state were obtained by adding the required amount of liquid electrolytes to a dry PEG/PAMPS polymer. Liquid electrolytes include organic solvents with high boiling points (-1-methyl-2-pyrrolidone (NMP) and γ-butyrolactone (GBL)) and a redox couple (alkali metal iodide salt/iodine). The optimized conditions for PEG/PAMPS-based gel electrolytes based on the salt type, the concentration of alkali metal iodide salt/iodine, and solvent volume ratio were determined to be NaI, 0.4 M NaI/0.04 M I₂, and NMP:GBL (7:3, v/v), respectively. The highest ionic conductivity and the liquid electrolyte absorbency were 2.58 mS cm^?1 and 3.6 g g^?1 at 25 °C, respectively. The ion transport mechanism in both the polymer gel electrolytes and liquid electrolytes is investigated extensively, and their best fits with respect to the temperature dependence of the ionic conductivity are determined with the Arrhenius equation.     

Preparation and application of magnetic poly(styrene-glycidyl methacrylate) microspheres

A novel method for the preparation of polymer-based, magnetic microspheres is proposed. Pre-made, poly(styrene-glycidyl methacrylate) (PS-GMA) particles of micron size were swollen by a mixture of N-methyl-2-pyrrolidone and water, and then incubated with superparamagnetic nanoparticles. The nanoparticles were allowed to diffuse into polymer microspheres during the incubation, became entrapped and made the polymer microspheres superparamagnetic. These magnetic PS-GMA microspheres were chemically modified and then coupled with single-stranded oligonucleotides as probes for DNA hybridization. The immobilized probes showed repeatable capture of target oligonucleotides.     

Preparation and characterization of poly(3,4-ethylenedioxythiophene) (PEDOT) using partially sulfonated poly(styrene-butadiene-styrene) triblock copolymer as a polyelectrolyte

An aqueous dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT) was prepared using a partially sulfonated poly(styrene-b-butadiene-b-styrene) (s-SBS) as a polyanion. For the preparation of s-SBS, poly(styrene-b-butadiene-b-styrene) was sulfonated to four different levels ranging from 44.1 to 64.8 mol%. These sulfonated polymers were characterized with IR spectroscopy and ¹H NMR analysis to confirm sulfonation reaction. The preparation of the PEDOT complex was carried out through the chemical polymerization method in which the EDOT monomer starts to polymerize in the presence of s-SBS, resulting in an aqueous dispersion of PEDOT/s-SBS complex. The DC conductivities of PEDOT/s-SBS complexes were found to increase from 0.0003 to 0.05 s/cm as the sulfonation level of the corresponding s-SBS increases, which is consistent with the data recorded by UV–vis spectrophotometer. From the XPS experiments, it was concluded that the concentration of PEDOT-rich phase in the PEDOT/s-SBS increases as the sulfonation level of s-SBS increase, thus facilitating the charge transport along the doped PEDOT chains.     

Sorption of water vapor into polyelectrolyte complex of poly(styrenesulfonic acid)/poly(4-vinyl-N-ethylpyridinium bromide)

Successive differential and integral sorptions of water vapor into the polyelectrolyte complex of poly (sty renesulfonic acid) / poly(4-vinyl-N-ethylpyridinum bromide) have been measured; films of stoichiometric (1/1 molar ratio) and nonstoichiometric (2/1 molar ratio) complex were employed in the experiments. Sorption isotherms have been also determined by using the values obtained from integral sorption experiments. The sorption data have suggested the following. (i) The rearrangement of polymer chains plays a relatively unimportant role in sorption of water. (ii) The relaxation motion of network chains is suppressed. (iii) The change of morphological structure caused by vapor sorption is obscure. (iv) The ionic character of the 1/1 complex is higher than that of 2/1 complex. (v) A small amount of water can be dispersed on specific polymer sites, but the sorption of a large amount of water is accompanied by an expansion of network structure. Points (i)-(v) have been consistently interpreted on the basis of the network structure and ionic character of this complex.     

Control of the temperature responsiveness of poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) copolymer using ultrasonic irradiation

Poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (poly(NIPAM-co-HEMA)) is a temperature-responsive copolymer that is expected to be applicable as an advanced functional polymeric material in various fields. In this study, a novel method was developed to control the responsive temperature of poly(NIPAM-co-HEMA) using an ultrasonic polymerization technique. Initially, the behavior of the reaction was investigated using NIPAM and HEMA monomers under ultrasonic irradiation. A high ultrasonic power was found to produce a high reaction rate and low number average molecular weight of the copolymer. The polydispersity of the synthesized copolymer was approximately 1.5 for all ultrasonic powers examined. In the early stage of the reaction, the molar fraction of NIPAM in the copolymer was lower than the initial molar fraction of the monomers. It was concluded that ultrasonic irradiation affected the initiation reaction and polymer degradation, but did not affect the propagation reaction. Furthermore, the effect of the ultrasonic irradiation conditions on the temperature responsiveness of the copolymer was investigated. The lower critical solution temperature (LCST) of the copolymer was found to increase with increasing ultrasonic irradiation time. In addition, in the early stages of the reaction, the measured values of the LCST were higher than the estimated values using copolymer composition. This can be attributed to some parts of the copolymer chain possessing a higher NIPAM fraction than the overall fraction due to different reactivities of the monomers and terminated radicals. This hypothesis was indirectly verified by the synthesis of a block copolymer from the PNIPAM homopolymer and HEMA monomer.     

Electrodeposition of polyaniline, poly(2-iodoaniline), and poly(aniline-co-2-iodoaniline) on steel surfaces and corrosion protection of steel

Polyaniline (PANi), poly(2-iodoaniline) (PIANi), and poly(aniline-co-2-iodoaniline) (co-PIANi) were synthesized using cyclic voltammetry in acetonitrile solution containing tetrabuthylammonium perchlorate (TBAP) and perchloric acid (HClO₄) on 304-stainless steel electrodes. Adherent and black polymer films were obtained on the electrodes. The structure and properties of these polymer films were characterized by FTIR and UV-vis spectroscopy and electrochemical method. The corrosion performance of PANi, PIANi, and co-PIANi coated electrodes were investigated in 0.5 M hydrochloric acid (HCl) solutions by potentiodynamic polarization technique, open circuit potential-time curves and electrochemical impedance spectroscopy, EIS. It was found that the PANi film could provide much better protection than PIANi, and co-PIANi and PANi films have barrier property as well as acting as passivator. On the other hand PIANi and co-PIANi films are acting as barrier coatings which were related with the prevention of cathodic reaction taking place at metal\electrolyte interface. EIS measurement shows that every coating gives protection efficiency of greater than 75% after 48 h of immersion time in corrosive test solution.     

Peculiarities of Photoprocesses in Poly(9,9-di-<Emphasis Type="Italic">n</Emphasis>-octylfluorenyl-2,7-diyl) Films Doped with Potassium Iodide

The spectral-luminescence properties of poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) films doped with potassium iodide are investigated. It is found that the addition of potassium iodide at concentrations of 0.1–1% leads to a drop in the degree of ordering of the PFO films and decreases the fluorescence intensity and lifetime of the polymer. The kinetics of photoluminescence of PFO–KI films is studied in nano-, micro-, and millisecond time bands. Analysis of the experimental data on long-term luminescence using the percolation model showed that the addition of potassium iodide to the polymer increases the degree of disordering of the film. Investigations of the effect of an external magnetic field on the PFO luminescence over a wide time range indicate a complex character of the time dependence of the magnetic effect. The changes in both the magnitude and sign of the magnetic effect g(B) are observed over the entire measured time range.     

Graft polymerization of poly(epichlorohydrin-g-poly((oxyethylene) methacrylate)) using ATRP and its polymer electrolyte with KI

This contribution demonstrates a synthesis of comb polymer consisting of a poly(epichlorohydrin) (PECH) backbone and poly(oxyethylene methacrylate) side chains. Atom transfer radical polymerization (ATRP) was used to directly initiate the chlorine atoms of PECH macroinitiator. The structure of comb polymer was characterized by nuclear magnetic resonance (¹H nuclear magnetic resonance) and Fourier transform infrared (FT-IR) spectroscopy, presenting the successful “grafting from” method using ATRP. The comb polymer was used as a polymer matrix for dissolving potassium iodide (KI) to prepare solid polymer electrolyte. FT-IR spectroscopy indicates that the potassium salts are dissolved in the polymeric matrix due to coordination interaction with the ether oxygens of graft copolymer. Differential scanning calorimetry showed that glass transition temperature (T _g) of polymer electrolytes continuously increased with increasing salt concentration up to 15 wt.%, mostly due to coordinative interactions between the potassium ions and the ether oxygens of polymer matrix. Ionic conductivity at room temperature increased with increasing salt concentrations up to 5 wt.% (maximum ionic conductivity ~3.7 × 10⁻⁵ S/cm), after which it gradually decreased.     

Sudan IV dye based poly(alkyloxymethacrylate) films for optical data storage

The polymer poly{1-[2′-methyl-4′-(2″-methylphenylazo) phenylazo]-2-(m-methacryloyloxyoctyloxy}naphthalene, where m = 6, 8, 10, is synthesized by free radical addition polymerization method for holographic optical data storage. Characterization of the polymers is done by formation of the holographic grating. A study of the dependence of diffraction efficiency of the grating formed on various parameters is presented. Surface relief gratings on these polymer films are created upon exposure to argon ion laser beams at 514.5 nm without any subsequent processing steps. The surface structure of the relief gratings has been investigated by atomic force microscopy. The depth of surface relief in a typical case is found to be around 40 nm.     

Morphologies and optical properties of poly(2,5-diethoxyphenylene) nanofibril arrays

An anodic aluminum oxide (AAO) membrane can be used as a template for the synthesis of nanostructures. In this paper, we have fabricated poly(2,5-diethoxyphenylene) (EtO-PPP) nanofibril arrays by oxidative coupling polymerization of 1,4-diethoxybenzene (DEB) within the pores of an AAO template. The detailed molecular structure of the polymer nanofibrils was characterized by using the infrared spectrum and the ¹H-NMR spectrum. We have used transmission electron microscopy, scanning electron microscopy, and atomic force microscopy to confirm the morphologies and images of the template and the fabricated nanometer scale of poly(2,5-diethoxyphenylene)nanofibril arrays. The experimental results demonstrate that the pores of the AAO membrane are regular and uniform, and parallel to each other. Furthermore, the EtO-PPP chains in the narrowest template-synthesized fibrils were oriented parallel to the pore axes of the AAO membrane, and perpendicular to the surface of the aluminum substrate. The polymer chain orientation is partially responsible for the enhanced conductivity. The ultraviolet absorption maximum shows that the polymer contains a better extended π-conjugation system along the poly(p-phenylene) backbone, which results in a longer-wavelength shift of the absorption band. The photoluminescence (PL) spectrum of nanofibril arrays exhibits a 5-nm blue shift of the emission in comparison with the unordered molecules. Received: 3 January 2002 / Accepted: 7 January 2002 / Published online: 17 December 2002 RID="*" ID="*"Corresponding author. Fax: +86-931/891-1100, E-mail: lihl@lzu.edu.cn     

Antibacterial activities of surface modified electrospun poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fibrous membranes

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane, with its excellent chemical and mechanical properties, has good potential for broad applications. However, due to its hydrophobic nature, microbial colonization is commonly encountered. In this work, electrospun PVDF-HFP fibrous membranes were surface modified by poly(4-vinyl-N-alkylpyridinium bromide) to achieve antibacterial activities. The membranes were first subjected to plasma pretreatment followed by UV-induced surface graft copolymerization of 4-vinylpyridine (4VP) and quaternization of the grafted pyridine groups with hexylbromide. The chemical composition of the surface modified PVDF-HFP electrospun membranes was studied by X-ray photoelectron spectroscopy (XPS). The morphology and mechanical properties of pristine and surface modified PVDF-HFP fibrous membranes were characterized by scanning electron microscopy (SEM) and tensile test, respectively. The antibacterial activities of the modified electrospun PVDF-HFP fibrous membranes were assessed against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). The results showed that the PVDF-HFP fibrous membranes modified with quaternized pyridinium groups are highly effective against both bacteria with killing efficiency as high as 99.9999%.     

Polymer electrolytes based on copolymer of poly(ethylene glycol) dimethacrylate and imidazolium ionic liquid

Polymer electrolytes based on the copolymer of N-vinylimidazolium tetrafluoroborate (VyImBF₄) and poly(ethylene glycol) dimethacrylate (PEGDMA) have been prepared. Ethylene carbonate (EC) and LiClO₄ are added to form gel polymer electrolytes. The chemical structure of the samples and the interactions between the various constituents are studied by FT-IR. TGA results show that these polymer electrolytes have acceptable thermal stability, are stable up to 155 °C. Measurements of conductivity are carried out as a function of temperature, VyImBF₄ content in poly(VyImBF₄-co-PEGDMA), and the concentration of EC and LiClO₄. The conductivity increases with PEGDMA and EC content. The highest conductivity is obtained with a value of 2.90 × 10^? 6 S cm^? 1 at room temperature for VP1/EC(25 wt.%)–LiClO₄ system, corresponding to the LiClO₄ concentration of 0.70 mol kg^? 1 polymer.     

Spin relaxation studies on conducting poly(tetrathiafulvalene)

Magnetic parameters and the relaxation behavior of paramagnetic centers in an iodine-doped poly(tetrathiafulvalene) semiconductor with a d.c. conductivity of 10^?5 S·cm^?1 have been studied using mainly the 2 mm waveband EPR technique in the temperature range of 110–270 K. The EPR line shape analysis confirms the existence of immobile radicals pinne on short polymer chains and mobile polarons with different relaxation parameters in slightly doped poly(tetrathiafulvalene). The temperature dependences of electron spin-lattice and spin-spin relaxation times of paramagnetic centers of both types have been determined independently using the saturation method at the operation frequency ν _e = 140 GHz. An anisotropic slow libration of immobile polarons with an activation energy of 0.02 eV have been registered for the first time using the saturation transfer EPR method. The temperature dependences of intrachain diffusion and interchain hopping rates in poly(tetrathiafulvalene) are determined from theT ₁ andT ₂ EPR data. The interchain spin dynamics is shown to correlate with libration of polarons trapped on polymer chains and is in good agreement with a hopping charge transport mechanism.     

Spectral studies of thin films based on poly(N-vinylcarzole) and red dopant

Organic light-emitting diodes were fabricated with a structure of indium-tin-oxide (ITO)/poly(N-vinylcarzole)(PVK):4-(dicyanom-ethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)/8-tris-hydroxyquinoline aluminum (Alq₃)/lithium fluoride (LiF)/Al. The energy transfer from PVK to Alq₃ then to DCJTB and the charge trapping processes were investigated by employing the photoluminescence (PL) and electroluminescence (EL) spectra. With increasing thickness of the Alq₃ layer, the PL and EL emission from PVK were decreased gradually, which indicated that the effective energy transfer occurred from PVK to Alq₃ and then from Alq₃ to DCJTB. At the same time, we found that the exciton recombination zone could be adjusted by controlling the Alq₃ layer thickness and the applied voltages. The effects of different DCJTB concentrations on the optical and electrical characteristics of the devices were investigated, and an obvious red-shift was observed with the DCJTB dopant concentrations increasing in the PL and EL spectra.     

The optical properties of the blends of CdSe nanocrystals and poly(N-vinylcarbazole)

The CdSe nanocrystals with different sizes were synthesized in aqueous solution through water-sol method using l-cysteine hydrochloride as the stabilizer. The pH-dependent optical properties of the CdSe nanocrystals were investigated. Furthermore, the CdSe nanocrystals were dispersed into chloroform by using a cationic surfactant, and mixed with poly(N-vinylcarbazole) (PVK) in different mass ratios. The investigation of the photoluminescence (PL) and absorption spectra of the CdSe:PVK blends suggested that energy transfer from the PVK excited states to the CdSe nanocrystals, and it is more efficient for the smaller size nanocrystals. In the meantime, it was found that the relative emission intensity of the CdSe nanocrystals to PVK in the blends depended on the mass ratios, and the emission from the CdSe nanocrystals was the strongest as the mass ratio of CdSe to PVK was 2:1.     

The influence of the preparation conditions on the energy disorder in poly(methylphenyl)silane films

The photoluminescence (T=5 K) and absorption (T=295 K) spectra and thermostimulated luminescence (T=5–300 K) curves of poly(methylphenyl)silane (PMPS) films are investigated as functions of the film thickness, annealing temperature, and oxygen content in air. It is revealed that the optical spectra and thermostimulated luminescence curves of PMPS films prepared in air at room temperature undergo changes after annealing at T=370–450 K. The assumption is made that the observed changes are associated with the formation of long polymer chain segments with a closer packing. This leads to an increase in the density of low-energy states of excitons and charge carriers. It is demonstrated that atmospheric oxygen substantially affects the formation processes and the energy disorder in the films prepared. The PMPS films are found to degrade after heating to T≥500 K.