A new method is described for the synthesis of soluble poly(1-methoxy-4-(2-ethylhexyloxy)-p-phenylenevinylene) (MEH−PPV) using N,N-dimethylformamide (DMF) as the solvent. Based on a modification of the traditional Gilch method, the polymerization of α,α‘-dibromo-2-methoxy-5-(2-ethylhexyloxy)xylene was conducted in DMF under a variety of experimental conditions. The resultant MEH−PPVs were characterized and compared to those prepared using analogous syntheses in tetrahydrofuran (THF). Characterization techniques included 1H NMR spectroscopy, UV−vis spectroscopy, and gel permeation chromatography (GPC). Although the molecular weights of the polymers prepared in DMF were routinely lower than those prepared in THF, the polydispersities were as low as (and in most cases lower than) those obtained using THF. Significantly, the use of DMF in polymerizations conducted at 100 °C led to no gelation of the polymer, which circumvented the need for any controlled addition of monomer during the reaction. Moreover, control over the polymer molecular weights in DMF could be achieved using chosen aliquots of the molecular weight modifier 4-(tert-butyl)benzyl bromide and/or by controlling the concentration of the reactants.

Successive surface reactions on hydrophilic silica substrates were designed and performed to immobilize ethanolamine-modified magnetic ferrite-based nanoparticle (NP) for surface characterization. The various surfaces were monitored using sum-frequency generation (SFG) spectroscopy. The surface of the hydrophilic quartz substrate was first converted to a vinyl-terminated surface by utilizing a silanization reaction, and then, the surface functional groups were converted to carboxylic-terminated groups via a thiol–ene reaction. The appearance and disappearance of the vinyl (CH2) peak at ∼2990 cm–1 in the SFG spectra were examined to confirm the success of the silanization and thiol–ene reactions, respectively. Acyl chloride (−COCl) formation from carboxy (−COOH) functional group was then performed for further attachment of magnetic amine-functionalized magnesium ferrite nanoparticles (NPs) via amide bond formation. The scattered NPs attached on the modified silica substrate was then used to study the changes in the spectral profile of the ethanolamine modifier of the NPs for in situ lead­(II) (Pb2+) adsorption at the solid–liquid interface using SFG spectroscopy. However, due to the limited number of NPs attached and sensitivity of SFG spectroscopy toward expected change in the modifier spectroscopically, no significant change was observed in the SFG spectrum of the modified silica with magnetic NPs during exposure to Pb2+ solution. Nevertheless, SFG spectroscopy as a surface technique successfully monitored the modifications from a clean fused substrate to −COCl formation that was used to immobilize the decorated magnetic nanoparticles. The method developed in this study can provide a reference for many surface or interfacial studies important for selective attachment of adsorbed organic or inorganic materials or particles.

In this communication we demonstrate the dependence of the solute order parameter on the solute molecular weight for polymer solutes dissolved in liquid crystalline solvents. Using ensemble absorption polarization spectroscopy together with single molecule fluorescence polarization measurements, we have determined the order parameter of the conjugated polymer MEH-PPV (poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene]) in the liquid crystal 5CB (4-cyano-4-n-pentylbiphenyl) as a function of polymer chain length. Ensemble absorption polarization measurements agree well with results obtained by single molecule fluorescence polarization spectroscopy, indicating a large-scale ordering of the MEH-PPV solute in 5CB. These results demonstrate that the increasing number of defects for larger polymer weights inherently limits the alignment of the polymer solute.

The preparation of dialkyl‐substituted poly(2,5‐didecyl‐1,4‐phenylene vinylene) (PDDPV) by the Horner‐Emmons polycondensation is described. Its performance in an organic light‐emitting diode (OLED) device architecture is compared with devices prepared from the analogous dialkoxy‐substituted poly(2,5‐didecyloxy‐1,4‐phenylene vinylene) (PDOPV) and the corresponding alkyl‐alkoxy‐substituted alternating copolymer. Additionally, the structure, stability, electrochemical, and optical properties of the PPVs were characterized by gel permeation chromatography, thermogravimetric analysis, NMR spectroscopy, cyclic voltammetry, UV‐Visible spectroscopy, and fluorescence spectroscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41162.