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See detailIn situ nitroxide-mediated polymerization of styrene promoted by the N-tert-butyl-alpha-isopropylnitrone/BPO pair: ESR investigations
Detrembleur, Christophe ULg; Clément, Jean-Louis; Sciannaméa, Valérie et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2013), 51(8), 1786-1795

The styrene polymerization initiated by benzoyl peroxide (BPO) in the presence of N-tert-butyl--isopropylnitrone as nitroxide precursor is well-controlled provided that a prereaction between the nitrone ... [more ▼]

The styrene polymerization initiated by benzoyl peroxide (BPO) in the presence of N-tert-butyl--isopropylnitrone as nitroxide precursor is well-controlled provided that a prereaction between the nitrone and BPO is carried out in suitable conditions prior to polymerization at a higher temperature. Electron spin resonance (ESR) spectroscopy was implemented to probe the nitroxides formed during both steps, that is, the prereaction and polymerization, and to get crucial information regarding the structure of the nitroxides responsible for the polymerization control. ESR studies combined with first principles calculations have evidenced that nitroxides observed during the prereaction in the presence of styrene and during the polymerization steps consist of a mixture of two macronitroxides. One is formed by the addition of a growing polystyrene chain to the nitrone as would be expected. However, the second one results from the addition of a polystyrene chain to tert-butyl nitroso that is in situ formed presumably by decomposition of the first macronitroxide type. [less ▲]

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See detailSelf-Assembled Film Organization in Fast Microcontact Printing Investigated by Sum Frequency Generation Spectroscopy
Lis, Dan; Peremans, André; Sartenaer, Yannick et al

in Journal of Physical Chemistry C: Nanomaterials, Interfaces, and Hard Matter (2009), 113

The ability of microcontact printing to build highly ordered alkanethiol self-assembled monolayers (SAMs) on Pt substrates within a short time is studied by sum frequency generation (SFG) spectroscopy and ... [more ▼]

The ability of microcontact printing to build highly ordered alkanethiol self-assembled monolayers (SAMs) on Pt substrates within a short time is studied by sum frequency generation (SFG) spectroscopy and contact angle measurements. The deposition of ordered hexadecanethiol and dodecanethiol monolayers onto platinum substrates is achieved in less than 1 s. The film order and the alkane chain orientation are deduced from the SFG fingerprint acquired under different sets of laser polarization. Comparisons between the SAMs prepared by printing or by immersion demonstrate that both methods lead to the same high quality organization. Patterning effects within printed films are also investigated with respect to the layer conformation. Finally, wetting properties of printed layers are correlated with the printing duration, corroborating the spectroscopic results. [less ▲]

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See detailJoint theoretical experimental investigation of the electron spin resonance spectra of nitroxyl radicals: application to intermediates in in situ nitroxide mediated polymerization (in situ NMP) of vinyl monomers
Zarycz, Natalia; Botek, Edith; Champagne, Benoit et al

in Journal of Physical Chemistry B (2008), 112(34), 10432-10442

Density functional theory (DFT) calculations have been performed to address the structure of nitroxide intermediates in controlled radical polymerization. In a preliminary step, the reliability of ... [more ▼]

Density functional theory (DFT) calculations have been performed to address the structure of nitroxide intermediates in controlled radical polymerization. In a preliminary step, the reliability of different theoretical methods has been substantiated by comparing calculated hyperfine coupling constants (HFCCs) to experimental data for a set of linear and cyclic alkylnitroxyl radicals. Considering this tested approach, the nature of different nitroxides has been predicted or confirmed for (a) the reaction of C-phenyl-N-tert-butylnitrone and AIBN, (b) N-tert-butyl-α-isopropylnitrone and benzoyl peroxide, (c) tert-butyl methacrylate polymerization in the presence of sodium nitrite as mediator, and (d) for the reaction of a nitroso compound with AIBN. Values of HFCC experimentally determined have been confirmed by DFT calculations. [less ▲]

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