Spectroscopic characterization of the conversion of poly(p-phenylene-vinylene) precursor by ion irradiation

Different spectroscopic techniques show that poly(p-phenylene vinylene) films can be derived from a sulphonium precursor by irradiation with ion beams at energies of the order of 100 keV. The comparison with the pyrolysis conversion shows less chlorine and sulfur residues in the irradiated thickness, whereas some ketone structures are evidenced. The formation of nanometric scale carbon clusters induced by the irradiation degradation of PPV is however indicated by UV spectrophotometry, leading to bandgap narrowing and increase of the conductivity. The irradiation with doping species allows the conversion and doping of PPV films in a single stage. The induced conductivity is limited by the formation of complexes with chlorine residues through a gettering process.     

Synthesis and interfacial properties of a novel inverse demulsifier of nanosized poly[(methyl methacrylate)-co-(ethyl acrylate)-co-(methacrylic acid)-co-(acrylamide)] latex

An acrylic emulsion-type inverse demulsifier (named as PMEMA latex) was prepared by using methyl methacrylate (MMA), ethyl acrylate (EA), methacrylic acid (MAA), and acrylamide (AM) as monomers. The effects of reaction conditions toward the copolymerization results were investigated by evaluating various evaluation parameters, including conversion, molecular weight, and diameter. In addition, the interfacial properties of PMEMA latex were investigated to study its demulsification mechanism about treating the O/W emulsion.     

New confined p-phenylenevinylene (PPV)-type polymer analogue of poly(phenylene sulfide)

A new confined p-phenylenevinylene (PPV)-type polymer (PPVS) has been synthesized using Wittig condensation. The chemical structure of the polymer was well defined by ¹H NMR, ¹³C NMR, and FTIR spectroscopic analysis. PPVS contains oligomeric PPV units separated by sulfide bridges in the main chain; it is fully soluble in common organic solvents and has a number-average molecular weight of 3500 g mol⁻¹. Thermogravimetric analysis and differential scanning calorimetry indicate that PPVS is amorphous, stable up to 360 °C in air and displays a glass transition temperature of 98 °C. The optical properties of the polymer were investigated by UV-visible absorption and photoluminescence spectroscopies. The polymer film absorbs at 375 nm and emits at 517 nm with a narrow emission spectrum. From the cyclic voltammetry analysis, the electrochemical bandgap was estimated to be 2.78 eV. A single-layer diode device of the configuration indium-tin oxide/PPVS/aluminium has been fabricated and has a relatively low turn-on voltage of 3.4 V. An electroluminescent emission similar to photoluminescence is demonstrated in a multilayer device.     

Synthesis and characterization of nano-sized poly[(butyl acrylate)-co-(methyl methacrylate)-co-(methacrylic acid)] latex via differential microemulsion polymerization

Poly[(butyl acrylate)-co-(methyl methacrylate)-co-(methacrylic acid)] latex particles were synthesized via differential microemulsion polymerization. The effect of initiator type and methacrylic acid incorporation were investigated. The initiator type could significantly affect the particle size and the molecular weight of the resulting polymer and 2,2′-azobisisobutyronitrile produced the smallest particle size. The incorporation of methyl methacrylate (MAA) in the copolymer and terpolymer structures was confirmed by FTIR and NMR spectroscopy, and DSC in that the carbonyl peak of carboxylic acid at 1,700 cm^?1 in the FTIR spectrum was observed when the MAA amount was high enough, the peak areas at 0.9 ppm in the NMR spectrum confirmed the participation of MAA from the increasing proton signals and the glass transition temperature and polarity of the polymer increased when the MAA amount was increased. This supported that the MAA was incorporated into the polymer chains. MAA was found to produce a vitrification effect during the polymerization.     

Swelling of hydrophobically modified poly(acrylamide) and poly(acrylamide)-co-(acrylic acid) gels in surfactant solutions

A series of hydrophobically modified polyacrylamide and polyacrylamide-co-poly(acrylic acid) gels with systematically varying hydrophobicity were prepared by free-radical polymerization of acrylamide, n-alkylacrylamides (n = 10, 12, and 14), and acrylic acid. The swelling of these gels was examined in water and in both anionic and cationic surfactant solutions. It was found that the gels which incorporated acrylic acid showed extremely high swelling in water. Maximum swelling was observed in gels which incorporated 10 mol% acrylic acid. The swelling of these gels was much less in solutions of both anionic and cationic surfactants than in water. The gels which did not incorporate acrylic acid demonstrated little swelling in water, but showed increased swelling in both anionic and cationic surfactant solutions with increased hydrophobicity of the gel. Received: 1 February 1999 Accepted in revised form: 5 March 1999     

The synthesis of poly(3,4-dihydroxystyrene) and poly[(sodium 4-styrenesulfonate)-co-(3,4-dihydroxystyrene)]

Poly(2-methoxy-4-vinylphenol), polyMVP, and poly[(sodium 4-styrenesulfonate)-co-(2-methoxy-4-vinylphenol)], poly(SSS/MVP), were synthesized by radical polymerization using Vazo-64 or tributylborane as initiator. Poly(3,4-dihydroxystyrene) and poly[(sodium 4-styrenesulfonate)-co-(3,4-dihydroxystyrene)] were obtained by demethylation of polyMVP and poly(SSS/MVP) using HBr and trimethylsilyl iodide, respectively. (Co)polymer structures were confirmed by ¹H and ¹³C NMR spectra. About 30 wt.-% gel formed in the polyMVP polymerizations, whereas only a small amount (0.5 mol-%) of gel formed in the copolymerizations.     

Evaluation of Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole as photostabilizer for poly(methyl methacrylate)

The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φ_cs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10^?5 and 8.75 × 10^?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested.     

Regiodefined substituted poly(2,5-thienylene)s

The polymerization of 3,3″-dialkylterthiophenes overcomes the lack of regiospecificity associated (to some extent) with all the polymerization methods in use, thus allowing the preparation of perfectly regioregular polymers endowed with enhanced electrical and optical properties. Moreover, the larger spacing of the alkyl chains achieved with the insertion of an unsubstituted thiophene unit confers to such regioregular polymers an extraordinary doping stability. Two regiochemically defined alkoxy-substituted terthiophenes were also polymerized and the effects of the effects of the presence and position of the alkoxy group on the polymerization reaction and on the polymer properties are discussed. © 1993 John Wiley & Sons, Inc.     

Fabrication of poly(p-phenylene vinylene) (PPV) nanoheterocomposite films via layer-by-layer adsorption

The fabrication of polyelectrolyte multilayer film architectures composed of a polycation precursor (Pre-PPV) of the electroluminescent poly(p-phenylene vinylene) (PPV) and two different counter-polyanions, cellulosesulfate and poly(vinylsulfate), are reported. All multilayers were characterized by UV/VIS-spectroscopy and X-ray reflectometry. Due to the differences in spatial arrangement of charged groups, rigidity, and conformation of the polyanions, the corresponding multilayer films differ in properties such as average thickness increments and surface roughness. The adsorbed amounts per layer can be adjusted by addition of inorganic salts. Thermal conversion of Pre-PPV to PPV is achieved already slightly above 100 °C, yielding identical absorption spectra for after either 3 h at 160 °C or 20 h at 120 °C. The heat treatment causes the film thickness to be reduced by 24–40% due to elimination of dimethylsulfide and HCl and also the loss of water, but the films stay optically transparent.     

Structure and properties of poly(2,5-dimethylterephthalamides)

Six methyl-substituted wholly aromatic polyamides were synthesized from the reaction of 2,5-dimethylterephthaloyl chloride with p-phenylenediamine, its 2,5-dimethyl and 2-methyl derivatives, m-phenylenediamine, or its 2-methyl and 4-methyl derivatives by solution polycondensation at low temperature. The x-ray diffraction diagrams of the polyamides obtained exhibit crystal patterns. Density values range from 1.26 to 1.37 g/cm³. NMR spectra determined in concentrated H₂SO₄ solution are reported. Poly(2,5-dimethylterephthalamides) have lower thermal stability than the corresponding polyterephthalamides. The increase in solubility of polyamide by the introduction of the 2,5-dimethylterephthaloyl linkage is accompanied by a decrease in thermal stability. The effect of methyl substituents on thermal properties and solubility is discussed in terms of the packing of polymeric molecules and the extent of hydrogen bonding of the amide groups.     

NMR study of doped poly(2,5-dimethylaniline)

Structure changes and charge transfer in the doping process of poly(2,5-dimethylaniline) (PDMA) were studied by NMR technique. It was shown that not only the polymer chain but also the hydrogen atoms and methyl groups on the aromatic rings were involved in the charge transfer process. A “four ring BQ derivatives” model was proposed to explain the NMR results.     

Conjugation of bioactive groups to poly(lactic acid) and poly[(lactic acid)-co-(glycolic acid)] films

A novel PLA-based polymer containing reactive pendent ketone or hydroxyl groups was synthesized by the copolymerization of L-lactide with epsilon-caprolactone-based monomers. The polymer was activated with NPC, resulting in an amine-reactive polymer which was then cast into thin polymeric films, either alone or as part of a blend with PLGA, before immersion into a solution of the cell adhesion peptide GRGDS in PBS buffer allowed for conjugation of GRGDS to the film surfaces. Subsequent 3T3 fibroblast cell adhesion studies demonstrated an increase in cellular adhesion and spreading over films cast from unmodified PLGA. Hence the new polymer can be used to obtain covalent linkage of amine-containing molecules to polymer surfaces.     

Synthesis and electrical conductivity of poly(arylene vinylene). I. Poly(2,5-dimethoxyphenylene vinylene) and poly(2,5-dimethylphenylene vinylene)

The highly conjugated aromatic polymers, poly(2,5-dimethoxyphenylene vinylene) and poly(2,5-dimethylphenylene vinylene), were obtained from their water soluble, sulfonium salt precursor polymers. Films of these polymers were reacted with either AsF₅ or I₂ vapor. Poly(2,5-dimethoxyphenylene vinylene) showed increases in electrical conductivity of up to 14 to 15 orders of magnitude for these two dopants, while an 8 to 9 order of magnitude increase was observed for poly(2,5-dimethylphenylene vinylene) with the same dopants. The synthesis of the precursor polymers, the properties and elimination reactions of films of the precursors, the doping reactions, and the conductivities of the resulting phenylene vinylene films are discussed.     

Synthesis and characterization of poly[(methylsilylene ethynylenephenyleneethynylene)-co-(dimethylsilylene ethynylenephenyleneethynylene)]s

<正>A series of poly[(methylsilylene ethynylenephenyleneethynylene)-co-(dimethylsilylene ethynylenephenyleneethynylene)]s were synthesized by the incorporation of various ratios of methylsilylene to dimethylsilylene units into the polymer chain backbone.The resultant copolymers were soluble in a variety of common organic solvents at room temperature.The copolymers were characterized by FT-IR,~1H-NMR,GPC,rheological analysis,differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA).The results showed that the copolymers exhibited good processability and cured at low temperatures like 200℃.The curing reactions involved in hydrosilylation of Si—H and alkyne groups and the polymerization of alkynes.Y_(d5)(5%weight loss) of the cured copolymers ranged from 629℃to 686℃,and the decomposition residues of cured copolymers at 1000℃ranged from 88.1%to 90.9%under nitrogen.Thermal stability of the copolymers increased with the introduction of methylsilylene units into polymer chains.The cured copolymers were sintered at 1450℃,and the results of X-ray diffraction analysis showed that β-SiC was formed in the sintered products.     

Synthesis and properties of poly(2,5-ethylene benzimidazole)

Methyl β-(3,4-diaminophenyl)propionate, its hydrochloride, and β-(3,4-diaminophenyl)propionic acid were prepared and their structures were established. The effect of temperature, time, and pressure on the polymerization of these compounds and the molecular weight and structure of the resulting polymers were examined. Thin films of different polymer samples were prepared by compression molding, and their infrared spectra were used to study their structures. Samples of poly(2,5-ethylene benzimidazole) formed under typical polymerization conditions were shown by differential scanning calorimetry and x-ray techniques to be amorphous, and the glass transition temperature ranged between 201 and 240°C. The polymers were shown by thermogravimetric analysis to have good thermal stability, and 29–34% of the original weights remained after heating to 1000°C in nitrogen.     

Synthesis and characterization of poly(1,4-phenylenevinylene-alt-2,5-thienylenevinylene) derivatives for organic light-emitting diodes

A new series of alternating copolymers composed of 1,4-phenylenevinylene and 2,5-thienylenylvinylene repeating units with various side chain substituents were synthesized via the Heck coupling reaction for use in light-emitting diodes (LEDs). The resulting copolymers were characterized using ¹H- and ¹³C-NMR, DSC, and TGA. These polymers were found to be soluble in common organic solvents and are easily spin-coated onto glass substrates, producing high optical quality thin films without defects. The electro-optical properties of ITO/PEDOT/Polymer/Al devices were investigated using UV-VIS, PL and EL spectroscopy. The turn-on voltages of these devices were found to be in the range 4-16 V, with a maximum brightness of about 2900 cd/m² at 12 V.     

Grafting reactions of vinyl acetate onto poly[(vinyl alcohol)-co-(vinyl acetate)]

The grafting preference of vinyl acetate onto the methine carbon of poly(vinyl alcohol) (PVOH) versus the acetate group of poly(vinyl acetate) (PVAc) was determined as part of an attempt to prepare novel branched PVOH from partially hydrolyzed PVAc. The results showed long chain grafting on the acetate groups of the PVAc units rather than the methine carbons of the PVOH or PVAc units. Decreasing the monomer or initiator concentration decreased the molecular weight of the graft copolymer formed. Of the initiators studied, ammonium persulfate gave the largest increase in copolymer molecular weight. Both hydrolysis and reacetylation combined with gel permeation chromatography (GPC) and ¹³C-NMR of the fully hydrolyzed material were used to estimate the number and location of grafts. © 1996 John Wiley & Sons, Inc.