Synthesis and properties of porous polyvinylamine microspheres from acrylonitrile

A novel route to synthesize crosslinked porous polyvinylamine (PVAm) microspheres from acrylonitrile (AN) was developed. In the first step, crosslinked porous polyacrylonitrile (PAN) spheres were prepared by copolymerization of AN and divinylbenzene (DVB). Then they were hydrolyzed to form polyacrylamide (PAM) spheres. And lastly, the porous PVAm spheres were successfully obtained via Hofmann degradation of PAM spheres. Scanning electron microscope (SEM) indicated that these PVAm microspheres have rough surfaces and porous interior structure. The pore size, the amino content, and the content of equilibrium water were also investigated. The pore size of these PVAm microspheres increased with the hydrolytic process. The contents of equilibrium water was changed from 49.6 to 96.5% depending on the different crosslinking degrees, and the amino contents were varied between 9.60 and 15.30 mmol/g depending on the different molar ratio of n(NaClO)/n(NaOH). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1674–1682, 2008     

Synthesis of ABCD 4‐Miktoarm star‐shaped quarterpolymers by combination of the “click” chemistry with multiple polymerization mechanism

Well‐defined ABCD 4‐Miktoarm star‐shaped quarterpolymers of [poly(styrene)‐poly(tert‐butyl acrylate)‐poly(ethylene oxide)‐poly(isoprene)] [star(PS‐PtBA‐PEO‐PI)] were successfully synthesized by the combination of the “click” chemistry and multiple polymerization mechanism. First, the poly(styryl)lithium (PS^?Li⁺) and the poly(isoprene)lithium (PI^?Li⁺) were capped by ethoxyethyl glycidyl ether (EEGE) to form the PS and PI with both an active ω‐hydroxyl group and an ω′‐ethoxyethyl‐protected hydroxyl group, respectively. After these two hydroxyl groups were selectively modified to propargyl and 2‐bromoisobutyryl group for PS, the resulted PS was used as macroinitiator for ATRP of tBA monomer and the diblock copolymer PS‐b‐PtBA with a propargyl group at the junction point was achieved. Then, using the functionalized PI as macroinitiator for ROP of EO monomer and bromoethane as blocking agent, the diblock copolymer PI‐b‐PEO with a protected hydroxyl group at the conjunction point was synthesized. After the hydrolysis, the recovered hydroxyl group of PI‐b‐PEO was modified to bromoacetyl and then azide group successively. Finally, the “click” chemistry between them was proceeded smoothly. The obtained star‐shaped quarterpolymers and intermediates were characterized by ¹H NMR, FT‐IR, and SEC in detail. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2154–2166, 2008     

Study of the effect of ligands on the fluorescence properties of terbium ternary complexes

Four ternary complexes of Tb(III) were synthesized by introducing the first ligand (L₁) (N-phenylanthranilic acid (N-HPA), α-furoic acid (FURA)) and the second ligand (L₂) (1,10-phenanthroline (Phen), 2,2′-dipyridyl (Bipy)), respectively. These complexes were characterized by elemental analysis, infrared spectra, XRD, UV spectra and fluorescence spectra. The effect of L₁ and L₂ on the fluorescence properties of terbium complexes was discussed. It showed that all the complexes exhibited ligand-sensitized green emission. The fluorescent intensity increased in the sequence of Tb(FURA)₃Bipy < Tb(N-PA)₃Phen < Tb(FURA)₃Phen < Tb(N-PA)₃Bipy. It indicated that L₁ affected fluorescence properties of the complexes differently when the corresponding L₂ altered. Meanwhile, the influence of L₂ on the luminescence properties of the complexes also depends on L₁. The results showed that L₁ and L₂ affected each other and worked together as a whole. The matching of L₁, L₂ and Tb³⁺ ion is very important to the luminescence properties of Tb(III) ternary complexes.     

吸流管道动力学模型的研究现状与展望

围绕吸流管道的稳定性与振动问题,对近年来的主要研究工作加以综述并提出预测,其中包括运动方程的归纳与讨论、管道自由端口处的流固耦合理论、定常流速下吸流管道的稳定性机理以及今后值得进一步研究的某些问题.     

新超复结构和Clifford分析

本文在Ｈ．Ｍａｌｏｎｅｋ［１］新的超复结构的意义下，研究Ｃｌｉｆｆｏｒｄ分析中Ａ值函数超复可微性及其一种新的锁链规则和微分法则．     

体上矩阵可中心化的判别定理

设Ｄ为任意一个体，本文得到判别体Ｄ上矩阵可中心化的几个定理。     

BIFURCATION SOLUTION BRANCHESAND THEIR NUMERICAL APPROXIMATIONS OF A SEMI-LINEAR ELLIPTIC PROBLEM WITH TWO PARAMETERS

1.IntroductionConsidertheequationdependingontheparametersA,pER,wheref'R-Rands:R-RaresmoothoddfunctionandLetS'u(x)-u(T--x),r={S,I}.Then(l.l)isr-equivalent.Theequality(l.Za)isjustanormalizationoffatx=0.WeintroduceaSobolevspaceX:=Ha(0,7),anddefineamappingT'gEL'(0,T)u'=TaEXimplicitly'Aweakformof(1.1)inXxRZisDuetof(0)~0,theproblem(1.3)(resp.(1))hasatrivialsolutioncurveIfwerestrictp=0,then(l.3)reducestoaproblemwithsingleparameteranditsbifurcationsonthetrivialsolutioncurveCOarewellknown,…     

Nilpotent sign patterns of a given index

A sign pattern is said to be nilpotent of index k if all real matrices in its qualitative class are nilpotent and their maximum nilpotent index equals k. In this paper, we characterize sign patterns that are nilpotent of a given index k. The maximum number of nonzero entries in such sign patterns of a given order is determined as well as the sign patterns with this maximum number of nonzero entries.     

Government-provided annuities under insolvency risk

This paper seeks to determine whether governments should intervene in the private annuity market by directly providing public insurance in the form of annuities when both the government and the insurance companies could default. It is found that, although the government could default, intervening by means of an annuity can improve social welfare if the insurance companies could default and the expected return on the public annuity is greater than the rate of return on a risk-free bond. We also find that, under actuarially fair pricing, the government should provide more in terms of a public annuity than the optimal amount of the annuity that the individual purchases in the private market if the government is less likely to default on the public annuity than an insurance company would in the case of a private annuity.