Synthesis of well‐defined polymers end‐functionalized with crosslinkable aziridine groups by living anionic polymerization

Well‐defined end‐functionalized polystyrene, poly(α‐methylstyrene), and polyisoprene with polymerizable aziridine groups were synthesized by the termination reactions of the anionic living polymers of styrene, α‐methylstyrene, and isoprene with 1‐[2‐(4‐chlorobutoxy)ethyl]aziridine in tetrahydrofuran at ?78 °C. The resulting polymers possessed the predicted molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.1) as well as aziridine terminal moieties. The cationic ring‐opening polymerization of the ω‐monofunctionalized polystyrene having an aziridinyl group with Et₃OBF₄ gave the polymacromonomer, whereas the α,ω‐difunctional polystyrene underwent crosslinking reactions to afford an insoluble gel. Crosslinking products were similarly obtained by the reaction of the α,ω‐diaziridinyl polystyrene with poly(acrylic acid)‐co‐poly(butyl acrylate). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4126–4135, 2005     

Production of laser-heated plasma in high- pressure Ar gas and emission characteristics of vacuum ultraviolet radiation from Ar2 excimers

A new pump scheme for the realization of a practical Ar₂ excimer laser operating at 126 nm has been proposed and investigated experimentally. In this scheme, pre-ionized high-pressure Ar gas was excited by an intense transversely-excited atmospheric (TEA) CO₂ laser irradiation. A 100-mm-long line plasma was successfully produced at an argon gas pressure of 2 MPa. The vacuum ultraviolet emission at 126 nm from the Ar₂ excimers was observed and its emission characteristics were investigated under various experimental conditions. Received: 10 December 2001 / Published online: 14 March 2002     

α,α‐Dibromotoluene as a monomer for poly (substituted methylene) synthesis: Magnesium‐mediated polycondensation of α,α‐dibromotoluene and magnesium/copper‐mediated copolycondensation of α,α‐dibromotoluene with 1,6‐dibromohexane

α,α‐Dibromotoluene 1 was found to be polymerized by the reaction with excess Mg to give poly(phenylmethylene)s 2 , whose main chains were partially dehydrogenated to carbon–carbon double bonds (C?C). The C?Cs in 2 can be brominated by treatment with Br₂. The polymerization mechanism was presumed to include the formation of Grignard reagents of various species with benzylic C? Br bonds and the nucleophilic attacks of the Grignard reagents to various compounds with benzylic C? Br bonds. Copolymerization of 1 with dichlorodimethylsilane successfully proceeded. Mg/Cu‐mediated copolycondensation of 1 with 1,6‐dibromohexane proceeded to give polymers that have similar compositions to those of random copolymers of ethylene and styrene. © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5661–5671, 2006     

Study of ion desorption induced by a resonant core-level excitation of condensed H2O using Auger electron photo-ion coincidence (AEPICO) spectroscopy combined with synchrotron radiation

Ion desorption induced by a resonant excitation of O 1s of condensed amorphous H₂O has been studied by total ion and total electron yield spectroscopy, nonderivative Auger electron spectroscopy (AES) and Auger electron photo-ion coincidence (AEPICO) spectroscopy. The spectrum of total ion yield divided by total electron yield exhibits a characteristic threshold peak at hν = 533.4 eV, which is assigned to the 4a₁ ← O 1s resonant transition. The AES at the 4a₁ ← O 1s resonance is interpreted as being composed of the spectator-AES of the surface H₂O, and the normal-AES of the bulk H₂O, where the 4a₁ electron is delocalized before Auger transitions. H⁺ is found to be the only ion species in AEPICO spectra measured at the 4a₁ ← O 1s resonance and at the O 1s ionization (hν = 560 eV). The electron kinetic energy dependence of the AEPICO yield (AEPICO yield spectrum) at the 4a₁ ← O 1s resonance is found to be greatly different from that at the O 1s ionization. The peak positions of the AEPICO yield spectrum at the 4a₁ ← O 1s resonance are found to correspond to those of the spectator-AES of the surface H₂O, which is extracted from the AES at the 4a₁ ← O 1s resonance. Furthermore, the AEPICO yield is greatly enhanced at the 4a₁ ← O 1s resonance as compared with that at the O 1s ionization. On the basis of these results, a spectator-Auger-stimulated ion desorption mechanism and/or ultra-fast ion desorption mechanism are concluded to be responsible for the H⁺ desorption at the 4a₁ ← O 1s resonance. The enhancement of the H⁺ yield is ascribed to the O---H anti-bonding character of the 4a₁ orbital.     

Mini-Maximizers for Reaction-Diffusion Systems with Skew-Gradient Structure

A reaction-diffusion system with skew-gradient structure is a sort of activator-inhibitor system that consists of two gradient systems coupled in a skew-symmetric way. Any steady state of such a system corresponds to a critical point of some functional. The aim of this paper is to study the relation between a stability property as a steady state of the reaction-diffusion system and a mini-maximizing property as a critical point of the functional. It is shown that a steady state of the skew-gradient system is stable regardless of time constants if and only if it is a mini-maximizer of the functional. It is also shown that the mini-maximizing property is closely related with the diffusion-induced instability. Moreover, by using the property that any mini-maximizer on a convex domain is spatially homogeneous, quite a general instability criterion is obtained for some activator-inhibitor systems. These results are applied to the diffusive FitzHugh-Nagumo system and the Gierer-Meinhardt system.     

Simple linear approximations to the likelihood equation for combining evidence in multiple 2×2 tables: A critique of conventional procedures

Summary The conventional procedures for a common odds ratio in multiple 2×2 tables are explored and critiqued. Three types of linear approximation to the likelihood equations under some models of common measures of association are used to derive the popular conventional estimators and test statistics. Some of them are derived using the model of the common standardized difference which is an unacceptable measure. The derivation provides us with some characteristics of the procedures. The advantages of procedures based on the conditional and unconditional likelihoods are discussed. The Institute of Statistical Mathematics     

Dynamic nuclear magnetic resonance and empirical force field studies of cannabidiol

Internal rotation of cannabidiol (1), its mono-(2) and dimethyl (3) derivatives has been studied by ¹H and ¹³C dynamic NMR spectroscopy. The free energy of activation for the rotation of C₃-C₂, bond that we have observed for cannabidiol of 14.7 kcal/mol at 22° in CDCl₃ is in contrast with values previously reported in the literature. Molecular mechanics simulation of the rotation of C₃-C₂, bond of a model structure (4) well reproduced the presently determined barrier height. Analysis of the calculated rotational transition state structure revealed severe nonbonded C₂H/O and C ₈/O interactions as the source of barrier. Calculations of other model structures indicate general occurrence of restricted rotation about the pivot bond of phenylcyclohexanes appropriately substituted at β-carbon of cyclohexane ring and at ortho position of phenyl ring. The fully substituted 2,6-dimethyl-1-(o,o'-dimethylphenyl) cyclohexane (10) is predicted to show atropisomerism.     

Radical copolymerization of alkyl 2‐norbornene‐2‐carboxylate with alkyl acrylates: Facile incorporation of norbornane framework into poly(alkyl acrylate)s

Radical copolymerization of alkyl 2‐norbornene‐2‐carboxylates (alkyl = Me 1a , nBu 1b ) with alkyl acrylates (alkyl = ethyl, methyl, and n‐butyl) was investigated. Copolymerization of 1a,b with the alkyl acrylates initiated by 1,1′‐azobis (cyclohexane‐1‐carbonitrile) at 85 °C proceeded to give random copolymers, although the homopolymerization of 1a,b did not proceed efficiently under the same conditions. Typically, bulk copolymerization of 1a with ethyl acrylate in a feed ratio of 1:3 ([ 1a ]:[EA]) afforded a copolymer with M_n = 33,300 containing 19.4 mol % of 1a unit in the composition. An increase of T_g derived from the incorporation of the rigid norbornane framework was observed, although the extent of the temperature rise was rather moderate. The ternary radical copolymerization of 1a,b /alkyl acrylate/N‐phenylmaleimide proceeded to give copolymers with the three repeating units in the main chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4597–4605, 2007     

A novel cyclization reaction of oxidodiazoalkanes: formation of pyrazoles and pyridazines

The thermal decomposition of dialkali metal salts of β- and γ-hydroxyketone tosyl-hydrazones in refluxing DME produced pyrazoles and pyridazines, respectively.