Kinetics and mechanisms of emulsion polymerization of vinylidene chloride. I. Effects of operating variables on the rate of polymerization and the number of polymer particles produced

Emulsion polymerization of vinylidene chloride was carried out at 50°C using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator, respectively. Contrary to the results so far reported, the stirring rate did not affect the progress of the polymerization and such an abnormal kinetic behavior as the rate of polymerization suddenly drops in the course of polymerization was not observed. The number of polymer particles produced was proportional to the 0.7 power of the concentration of emulsifier forming micelles and to the 0.3 power of the initial initiator concentration, respectively, and was independent of the initial monomer concentration. The rate of polymerization was in proportion to the 0.3 power of the concentration of emulsifier forming micelles, to the 0.5 power of the initial initiator concentration, to the 0.2 power of the initial monomer concentration, and to the 0.45 power of the number of polymer particles, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1919–1928, 1998     

Investigating consumers’ store-choice behavior via hierarchical variable selection

Advances in Data Analysis and Classification - This paper is concerned with a store-choice model for investigating consumers’ store-choice behavior based on scanner panel data. Our...     

Molecular orientation of paramagnetic metal complex by melt-drawing thermotropic liquid crystalline polymers

New liquid-crystalline polyesters and paramagnetic vanadyl complex were prepared as host polymer and guest complex. Melt-drawn fibers were made from the blend of host polymer and guest complex at the mesophase temperature. ESR spectra of the melt-drawn fibers indicated that the base of pyramidal vanadyl complex is completely oriented parallel to the fiber axis.     

Beyond Reduction Cocatalysts: Critical Role of Metal Cocatalysts in Photocatalytic Oxidation of Methane with Water**

Environmentally sustainable and selective conversion of methane to valuable chemicals under ambient conditions is pivotal for the development of next-generation photocatalytic technology. However, due to the lack of microscopic knowledge about non-thermal methane conversion, controlling and modulating photocatalytic oxidation processes driven by photogenerated holes remain a challenge. Here, we report novel function of metal cocatalysts to accept photogenerated holes and dominate selectivity of methane oxidation, which is clearly beyond the conventional concept in photocatalysis that the metal cocatalysts loaded on the surfaces of semiconductor photocatalysts mostly capture photogenerated electrons and dominate reduction reactions exclusively. The novel photocatalytic role of metal cocatalysts was verified by operando molecular spectroscopy combined with real-time mass spectrometry for metal-loaded Ga₂O₃ model photocatalysts under methane and water vapor at ambient temperature and pressure. Our concept of metal cocatalysts that work as active sites for both photocatalytic oxidation and reduction provides a new understanding of photocatalysis and a solid basis for controlling non-thermal redox reactions by metal-cocatalyst engineering.     

Pnictogen-Bridged Diphenyl Sulfones as Photoinduced Pnictogen Bond Forming Emission Motifs

In this study, pnictogen (Pn)-bridged diphenyl sulfones were synthesized as motifs for photoinduced dynamic rearrangement. The newly synthesized sulfones exhibited dual fluorescence at 298 K. Density functional theory calculations revealed that the longer-wavelength fluorescence was derived from the geometries after structural relaxation through photo-driven pnictogen bond formation between the O atom lone pair of the sulfonyl moiety and the antibonding orbital of the Pn−C bond. This is the first report on emission dynamics driven by pnictogen bond formation upon photoexcitation.     

Reductive dimerization and reduction of imines using lanthanum metal

The treatment of N‐benzylideneaniline ( 1a ) with a half‐equivalent of lanthanum metal and a catalytic amount of iodine gave the reductive dimerization product of 1a , a vic‐diamine, in good yield. Various vic‐diamines were synthesized from aldimines in this manner in moderate to good yields. Our findings suggest that electrons of a zero‐valent lanthanum metal were efficiently utilized in this reductive dimerization. In the reaction of ketimines, however, a similar reductive dimerization did not take place, and the corresponding amines were formed as the sole products. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:131–135, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10007