The semicontinuous polymerization of methyl methacrylate (MMA) in heterogeneous medium under monomer‐starved conditions is reported here. The effect of monomer addition rate on kinetics, particle size, particle number, and PMMA average molar masses are reported. This process permits the synthesis of high‐solid content latexes containing nano‐sized particles (<40 nm) with narrow particle size distributions [(Dw/Dn) < 1.1]. Moreover, the molar masses (Mn ≈ 0.3–1.2 × 106 g/mol) are much lower than those expected by chain transfer to monomer, which is the typical termination mechanism in 0–1 emulsion and microemulsion reactions. Both particle size and average molar masses decrease as the rate of monomer addition is diminished. Possible explanations for this process are provided. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1463–1473, 2007

Two series of 2,5‐di(butoxy)phenyleneethynylenes, one halogenated (nPEC4‐X; n=2, 3, or 4) and the other boron‐dipyrromethene (BODIPY) terminated (nPEC4‐By; n=3, 4, or 5; By=BODIPY), were synthesized monodirectionally by the step‐by‐step approach and the molecular structure was corroborated by NMR spectroscopy (1H, 13C‐DEPTQ‐135, COSY, HSQC, HMBC, 11B, 19F) and MALDI‐TOF mass spectrometry. The multiplicity and J‐coupling constants of 1H, 11B, and 19F/11B NMR signals revealed, in the nPEC4‐By series, that the phenyl in the meso position of BODIPY becomes electronically part of the conjugation of the phenyleneethynylene chain, whereas BODIPY is electronically isolated. The photophysical, electrochemical, and theoretical studies confirm this finding because the properties of nPEC4‐By are comparable to those of the nPEC4‐X oligomers and BODIPY, indicating negligible electron communication between BODIPY and the nPEC4 moieties. Nevertheless, energy transfer (ET) from nPEC4 to BODIPY was rationalized by spectroscopy and theoretical calculations. Its yield decreases with the nPEC4 conjugation length, according to the increase in distance between the two chromophores, resulting in dual emission for the longest oligomer in which ET is quenched.

SummaryA novel and facile method was developed to produce hybrid graphene oxide (GO)–polyelectrolyte (PE) capsules using erythrocyte cells as templates. The capsules are easily produced through the layer-by-layer technique using alternating polyelectrolyte layers and GO sheets. The amount of GO and therefore its coverage in the resulting capsules can be tuned by adjusting the concentration of the GO dispersion during the assembly. The capsules retain the approximate shape and size of the erythrocyte template after the latter is totally removed by oxidation with NaOCl in water. The PE/GO capsules maintain their integrity and can be placed or located on other surfaces such as in a device. When the capsules are dried in air, they collapse to form a film that is approximately twice the thickness of the capsule membrane. AFM images in the present study suggest a film thickness of approx. 30 nm for the capsules in the collapsed state implying a thickness of approx. 15 nm for the layers in the collapsed capsule membrane. The polyelectrolytes used in the present study were polyallylamine hydrochloride (PAH) and polystyrenesulfonate sodium salt (PSS). Capsules where characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and Raman microscopy, the constituent layers by zeta potential and GO by TEM, XRD, and Raman and FTIR spectroscopies.

Summary: One of the most optically transparent magnetic materials known at room temperature consists of nanocrystalline γ‐Fe2O3 dispersed in a DVB cross‐linked sulfonated polystyrene (PS) matrix. When attrited dry or in water without surfactant and subsequently processed in water or water miscible liquids, the nanocomposite leads to a highly stable, low optical density ferrofluid with unique properties and uses in a variety of applications. We have heretofore identified the stabilizing agent in the ferrofluid as low molecular weight (∼6000) sulfonated PS, which results from attrition of the cross linked polystyrene nanocomposite. We report on the synthesis of low molecular weight (LMW) PS by atom transfer radical polymerization (ATRP) followed by sulfonation with acetyl sulfate and on the one‐step synthesis of a stable ferrofluid of nanocrystalline Fe3O4 using the newly synthesized LMW sulfonated PS. Physicochemical analyses and characterizations include GPC, GC‐MS, GPC, NMR, FTIR, XRD, TEM and magnetic data.

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