Anionic polymerization of methacrylates by samarium (III) enolate on networked polystyrene: Effects of its sterically confined environment on polymerization behavior

Anionic polymerization of methacrylates under sterically confined environment in a spherical beads‐shaped networked polystyrene (NwPS) matrix is described. The initiator used herein is a samarium (Sm) (III) enolate, which was formed by treatment of 2‐bromoisobutylate immobilized in the side chain of NwPS with Sm (II) iodide. By using this NwPS‐bound initiator, polymerization of a series of methacrylates (=solid‐supported polymerization) was studied to find its two aspects: (1) In the early stages, the rate constant for each methacrylate was comparable to that for its conventional solution‐phase polymerization using a Sm (III) enolate, suggesting that methacrylate can be efficiently supplied to the propagating end by its free permeation without any interference by the networked structure of the matrix. (2) After the early stages, the rate constant decreased remarkably, implying that permeation of methacrylate was sterically interfered by the formed poly(methacrylate) that filled the confined space in NwPS, as supported by a SEM image of the resulting beads, of which pores were filled with the formed polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1510–1521, 2009     

Biradical character of linear π-conjugated oligomer dications composed of thiophene, pyrrole, and methylthio end-capping units

Combined DFT calculations and UV-vis-NIR, ESR, and SQUID measurements revealed that the ground-state electronic structure of a linear π-conjugated oligomer dication composed of two pyrrole and six or seven thiophene rings and methylthio end-capping units is dominated by a singlet biradical character.     

Test compounds for detecting the silanol effect on the elution of ionized amines in reversed‐phase LC

The effectiveness of several basic compounds for testing silica‐based stationary phases was reviewed by applying them to recent columns for reversed‐phase HPLC. Most octadecylsilylated (C18) stationary phases, prepared as a base‐deactivated material from high‐purity silica gel with endcapping, provided excellent peak shape and column efficiency for the bases including benzylamine and amitriptyline that once caused problems and were subsequently employed for testing silanol activities. However, a cyclic tertiary amine, dextrometorphan, was eluted as an acceptable peak from only a few columns at neutral pH. Such a more sensitive probe is expected to contribute to further improvement of the stationary phase for reversed‐phase HPLC.     

Kaempferol glycosides in the flowers of carnation and their contribution to the creamy white flower color

Three flavonol glycosides were isolated from the flowers of carnation cultivars 'White Wink' and 'Honey Moon'. They were identified from their UV, MS, 1H and 13C NMR spectra as kaempferol 3-O-neohesperidoside, kaempferol 3-O-sophoroside and kaempferol 3-O-glucosyl-(1 --> 2)-[rhamnosyl-(1 --> 6)-glucoside]. Referring to previous reports, flavonols occurring in carnation flowers are characterized as kaempferol 3-O-glucosides with additional sugars binding at the 2 and/or 6-positions of the glucose. The kaempferol glycoside contents of a nearly pure white flower and some creamy white flower lines were compared. Although the major glycoside was different in each line, the total kaempferol contents of the creamy white lines were from 5.9 to 20.9 times higher than the pure white line. Thus, in carnations, kaempferol glycosides surely contribute to the creamy tone of white flowers.     

Theoretical study on quantum dynamics of bose system interacting with photon field

We investigate the quantum dynamics of two‐boson and two‐level systems interacting with a one‐mode photon field. The time evolution of the population for each state is calculated in terms of the Jaynes–Cummings model. We find the collapses and revivals of the order parameter for the Bose–Einstein condensation. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 401–408, 2001     

Samarium enolate on crosslinked polystyrene beads. III. Anionic initiator for well‐defined synthesis of poly(hydroxyethyl methacrylate) on solid support

A solid‐supported samarium enolate successfully initiated the polymerization of 2‐(trimethylsilyloxy)ethyl methacrylate (TMS‐HEMA) through the living anionic process. In addition, the silyl group was readily removed by treatment of the beads with a weak acid to afford the corresponding well‐defined poly(methacrylate) having a hydroxyethyl group in the side chain (PHEMA). The hydroxyl group of the immobilized PHEMA on the beads was successfully acetylated to give poly(2‐acetoxyethyl methacrylate), which could be quantitatively isolated from the beads by trifluoroacetic acid treatment. Moreover, the hydroxyl group of the immobilized PHEMA could be utilized as an initiator for acid promoted ring opening polymerization of lactone to yield the corresponding graft copolymer. In this method, the residual and excess reagents could be removed by filtration, which demonstrated the applicability of the present technique to a novel method for construction of functional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4417–4423, 2004     

Exciton dynamics in nanostar dendritic systems using a quantum master equation approach: core monomer effects and possibility of energy transport control

The directional energy transport, i.e. exciton migration, in nanostar dendritic systems composed of two-state monomer units is studied using a quantum master equation approach. We examine the effects of the variation in the excitation energy of the monomer in the core region (core monomer) on the multistep exciton migration from the periphery to the core based on the relaxation factors among exciton states originating in weak exciton-phonon coupling. It turns out that when the core monomer possesses both an excitation energy slightly lower than that of the first generation and a partial exciton overlap with the first generation, more efficient and rapid exciton migration to the core is expected as compared with other core monomer cases with the energy level closer to or much lower than that of the first generation.     

Upper Limit of Nitrogen Content in Carbon Materials

Nitrogen‐doped carbon materials (NDCs) play an important role in various fields. A great deal of effort has been devoted to obtaining carbon materials with a high nitrogen content; however, much is still unknown about the structure of the nitrogen‐doped materials and the maximum nitrogen content possible for such compounds. Here, we demonstrate an interesting relationship between the N/C molar ratio and the N content of NDCs. The upper limit for the nitrogen content of NDCs that might be achieved was estimated and found to strongly depend on the carbonization temperature (14.32 wt % at 1000 °C and 21.66 wt % at 900 °C), irrespective of the precursor or preparation conditions. Simulations suggest that, especially in the carbon architectures obtained at high temperatures, nitrogen atoms are always located on separate hexagon moieties in a graphitic configuration, thereby yielding a critical N/C molar ratio very close to the value estimated from the experimental results.