From “Living” Carbocationic to “Living” Radical Polymerization

Abstract

“Living” carbocationic polymerization is compared to the “living” radical process. Similarities and differences are discussed. “Living” radical polymerization of vinyl acetate and methyl methacrylate to provide polymers with controlled molecular weights and narrow molecular weight distribution (M_w/M_n < 1.2) are presented.     

From Living to “Immortal” Polymerization

Aluminum porphyrin is an excellent initiator for the living polymerizations of a wide variety of monomers such as epoxide, β-lactone, δ-lactone, ε-lactone, and lactide, and also for the alternating copolymerization of epoxide and cyclic acid anhydride or carbon dioxide, to give polymers and copolymers with narrow molecular weight distribution. Aluminum porphyrin was recently found to initiate also the living polymerization of methacrylic ester. In the polymerizations of epoxides and lactones initiated with aluminum porphyrin in the presence of an appropriate protic compound, polymers with narrow molecular weight can be obtained with the number of the polymer molecules more than those of the initiator. This fact demonstrates the “immortal” nature of the polymerization due to unusual reactivities of aluminum prophyrin.     

Introduction to“Chemical Journal of Chinese Universities”

<正>"Chemical Journal of Chinese Universities"(Chinese Edition) is a comprehensive academic journal in the field of chemistry sponsored by Jilin University and Nankai University mandated by the Educational Ministry of China and published by the Higher Education Press in China.Its original journal name was"Natural Science Journal of Chinese Universities"(Chemistry and Chemical Engineering Edition) started in 1964,and was     

Introduction to “Chemical Journal of Chinese Universities”

“Chemical Journal of Chinese Universities”（Chinese Edition） is a comprehensive academic journal in the field of chemistry sponsored by Jilin University and Nankai University mandated by the Educational Ministry of China and published by the Higher Education Press in China. Its original journal name was “Natural Science Journal of Chinese Universities”（Chemistry and Chemical Engineering Edition） started in 1964, and was changed into the present journal name in 1980. Since 1985, the journal has been published monthly. Now the journal format is 16 mo（A4） and the total pages CN22-1131/06 and the international journal number for each issue is 208. The domestic journal number is ISSN 0251-0790.     

Introduction to “Chemical Journal of Chinese Universities”

<正>"Chemical Journal of Chinese Universities"(Chinese Edition) is a comprehensive academic journal in the field of chemistry sponsored by Jilin University and Nankai University mandated by the Educational Ministry     

Introduction to “Chemical Journal of Chinese Universities”

<正>"Chemical Journal of Chinese Universities"(Chinese Edition) is a comprehensive academic journal in the field of chemistry sponsored by Jilin University and Nankai University mandated by the     

Introduction to “Chemical Journal of Chinese Universities”

"Chemical Journal of Chinese Universities"(Chinese Edition)is a comprehensive academic journal in thefield of chemistry sponsored by Jilin University and Nankai University mandated by the Educational Ministry of     

Introduction to “Chemical Journal of Chinese Universities”

＂Chemical Journal of Chinese Universities＂（Chinese Edition） is a comprehensive academic journal in the field of chemistry sponsored by Jilin University and Nankai University mandated by the Educational Ministry of China and published by the Higher Education Press in China. Its original journal name was ＂Natural Science Journal of Chinese Universities＂（Chemistry and Chemical Engineering Edition） started in 1964, and was changed into the present journal name in 1980. Since 1985, the journal has been published monthly.     

Introduction to “Chemical Journal of Chinese Universities”

<正>"Chemical Journal of Chinese Universities"(Chinese Edition)is a comprehensive academic journal in thefield of chemistry sponsored by Jilin University and Nankai University     

Introduction to “Chemical Journal of Chinese Universities”

<正>"Chemical Journal of Chinese Universities"(Chinese Edition) is a comprehensive academic journal in the field of chemistry sponsored by Jilin University and Nankai University mandated by the Educational Ministry     

Introduction to “Chemical Journal of Chinese Universities”

<正>"Chemical Journal of Chinese Universities"(Chinese Edition) is a comprehensive academic journal in the field of chemistry sponsored by Jilin University and Nankai University mandated by the Educational Ministry of China and published by the Higher     

Response to “About acceptance and rejection zones”

Desimoni and Brunetti raise some questions about the use of Eurachem/CITAC guide, because the Eurachem/CITAC guide does not discuss an ISO recommendation before performing a test, it should be decided whether it is to be a test for conformity or a test for non-conformity. In response, it is pointed out that although this recommendation is not discussed explicitly, it is of necessity covered by the decision rule that describes how the measurement uncertainty will be taken into consideration with regard to accepting or rejecting a product according to its specification and the result of a measurement. In addition, they propose the introduction of an ‘inconclusive’ zone. We do not think that this is necessary, since the Eurachem/CITAC guide takes the view that action on rejection should be covered by the ‘decision rule’ and this can make equivalent provision for confirmation or interpretation.     

Reply to comment on “liquid metal transport properties”

Abstract

The method^1,2 used to determine energy parameters with which to correlate liquid metal transport properties yields relative and not absolute values for these parameters. The choice of a reference substance and its value of E/k is arbitrary. Professor Collings' point is well taken that one might as well use an up-to-date value of E/k for the energy parameter of the reference substance. Nevertheless, one should not expect close agreement values of energy parameters determined from liquid metal viscosity and diffusivity data and values determined from neutron scattering experiments. Preston et a1.² found some disagreement between E/k values obtained from liquid transport data and values obtained from gas viscosity data for the rare gases. The asumption of the validity of the law of corresponding states for liquid metals is certainly more questionable than its applicability to the rare gases.     

Vanadium pentoxide gels: From “chimie douce” to “matière molle”

This article presents a review of the colloidal and liquid-crystalline properties of vanadium pentoxide suspensions from a physicist's perspective. The processes occurring during the synthesis of these suspensions are first discussed. Then, the liquid-crystalline properties of V₂O₅ sols and gels are described. These nematic phases are easily aligned by weak magnetic fields or by alternative electric fields. The delicate interplay between repulsive hardcore and electrostatic interactions and van der Waals attractions defines the (concentration, ionic strength) phase diagram that includes an isotropic phase, a uniaxial nematic phase, a biaxial nematic gel state and a flocculated state. Deuterium NMR spectroscopy of D₂O molecules gives information on the rotational dynamics of the nematic phase. Finally, various applications of these colloidal suspensions in the fields of hybrid organic/inorganic materials, mesoporous solids, and of the structures of biomolecules, are reviewed.     

Supercritical Drying Applied to Natural “Gels”: Allophanic Soils

Allophanic soils behave as gels during a classical drying with an important irreversible shrinkage which can modify the soil physical properties. These soils are interesting in terms of mitigation of the greenhouse effect (C sequestration) and the knowledge of the true soils features are of importance. Like for silica gels, we use the CO₂ supercritical drying procedure (SCD) to control the drying step. The objective is to preserve the structural and textural properties of the soils, which can be affected by the classical drying. We show also that despite the necessary solvent exchange and high pressure of the supercritical drying, the chemical composition and the allophanic features are not strongly affected.The textural properties such as specific surface area are higher for the supercritical dried samples compared to the classical dried samples, indicating the preserving effect of the SCD and showing the interest of the application of this drying method to this natural and complex “gels”. With these data, we show possible effects of the specific surface area on the C and N content of the allophanic soils.     

“Golden” Cascade Cyclization to Benzo[c]-Phenanthridines

Herein, we describe a gold-catalyzed cascade cyclization of Boc-protected benzylamines bearing two tethered alkyne moieties in a domino reaction initiated by a 6-endo-dig cyclization. The reaction was screened intensively, and the scope was explored, resulting in nine new Boc-protected dihydrobenzo[c]phenanthridines with yields of up to 98 %; even a π-extension and two bidirectional approaches were successful. Furthermore, thermal cleavage of the Boc group and subsequent oxidation gave substituted benzo[c]phenanthridines in up to quantitative yields. Two bidirectional approaches under the optimized conditions were successful, and the resulting π-extended molecules were tested as organic semiconductors in organic thin-film transistors.     

The Design of Second-order Nonlinear Optical Dendrimers: From “Branch Only” to “Root Containing”

Dendrimers are considered as a promising family of organic second-order nonlinear optical (NLO) polymers because of their well-defined structures,easily modified peripheral functional groups,interior branches and central cores.In order to obtain NLO materials with high performance,dendrimer structures have been optimized in the past years,such as the "branch only" and the "root containing" type dendrimers.This feature article highlights the achievements in exploring the rational design of dendrimers,partially marked by their macroscopic NLO performance.