Synthesis of mikto‐topology star polymer containing one cyclic arm

Well‐defined mikto‐topology star polystyrene composed of one cyclic arm and four linear arms was synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu‐catalyzed azide‐alkyne cycloaddition (CuAAC) click reaction. First, the bromine‐alkyne α,ω‐linear polystyrenes containing four hydroxyl groups protected with acetone‐based ketal groups were synthesized by ATRP of styrene using a designed initiator. Then, the bromine end‐group was converted to the azide and the linear polystyrene was cyclized intra‐molecularly by the CuAAC reaction. The four hydroxyl groups were released by deprotection and then esterified with 2‐bromoisobutyryl bromide to produce a cyclic polymer bearing four ATRP initiating units. By subsequent ATRP of styrene to grow linear polymers with the cyclic polystyrene as a macroinitiator, the mikto‐topology star polymers were prepared. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of tetrasubstituted thiophenes from pyridinium 1,4-zwitterionic thiolates and modified activated alkynes

Pyridinium 1,4-zwitterionic thiolates were applied to a formal [3 + 2] annulation reaction with modified activated alkynes, affording various tetrasubstituted thiophenes with aryl, alkenyl, alkyl or silyl group at the special position. The structural modification of alkyne substrates enabled the synthesis of diverse thiophenes to be achieved using the pyridinium 1,4-zwitterionic thiolates as the sulfur-containing building blocks. This approach is metal-free and catalyst-free.     

SYNTHESIS AND PROPERTIES OF ANILING ANILING AND 0-AMINOBENZENESULFONIC ACID COPOLYMER*

Poly(aniline- co-o-aminobenzenesulfonic acid) (PAOABSA) as a water soluble conducting polymerwas synthesized by chemical polymerization. The productivity and the room-temperature conductivity of thecopolymer were measured as a function of the reaction conditions, such as reaction temperature, the ratio ofoxidant to monomer and the degree of sulfonation defined as the ratio of sulfur to nitrogen atoms(S/N). Themain results obtained are summarized as follows : (1) lower reaction temperature (at about 0℃) is favorablefor the enhancement of the room-temperature conductivity of the copolymer; (2) higher content of oxidant isunfavorable for increasing the room-temperature conductivity of the copolymer; (3) both productivity androom-temperature conductivity of the copolymer decrease with increase of the degree of sulfonation whichwas always lower than 0.5 even an excess of o-aminobenzenesulfonic acid was added, probably because thereactivity ratio of aniline (γ=2.99± 0.05) is much higher than that of o-aminobenzenesulfonic acid (γ_2 = 0.06±0.02) estimated by using Fineman-Ross method and least square method.     

The effects of large oscillating fields on spin precession in magnetic resonance

Magnetic resonance of a spin system which is acted upon by a large near-resonance oscillating magnetic field transverse to a static field has been studied experimentally and theoretically for many years. The technique of DEMUR (Double Electron Muon Resonance) has many advantages for such studies. This paper will describe the results of an experiment to study the precession of the muonium triplet near magnetic resonance using DEMUR.     

Quadrupole interaction in In0.95 Ag0.045 Ga0.005 alloy

The temperature dependence of the quadrupole interaction of¹¹¹Cd in the In_0.95 Ag_0.045 Ga_0.005 alloy is determined by the time differential perturbed angular correlation method from 77 to 422 K. The electric field gradients produced by the lattice are derived. The temperature dependence of the electric field gradient is found to follow theT ^3/2 law observed in In between 77 K and room temperature and to deviate from it at higher temperatures. The widths of the electric field gradient distribution are 0.1147(259), 0.0924(340), 0.4954(601) and 1.344(175) at 77, 298, 373 and 422 K, respectively. This illustrates that the alloy is well ordered at 77 and 298 K and that it becomes less ordered at 373 and 422 K.