Room-temperature polymeric magnet

The structure of the pyrazine complex was suggested to contain polymeric square planar cations with bridging pyrazines and the magnetic properties (300-80K) were interpreted in terms of an antiferromagnetic exchange interaction. A Curie-Weiss constant of 84 K was calculated. At room temperature, the magnetic moment was found to be 1.61 BM. 

Cyanoacrylate adhesives (Super-Glues) are materials which rapidly polymerize at room temperature. The standard monomer for a cyanoacrylate adhesive is ethyl 2-cyanoacrylate [7085-85-0], which readily undergoes anionic polymerization. Very rapid cure of these materials has made them widely used in the electronics industry for speaker magnet mounting, as weU as for wire tacking and other apphcations requiring rapid assembly. Anionic polymerization of a cyanoacrylate adhesive is normally initiated by water. Therefore, atmospheric humidity or the surface moisture content must be at a certain level for polymerization to take place. These adhesives are not cross-linked as are the surface-activated acryhcs. Rather, the cyanoacrylate material is a thermoplastic, and thus, the adhesives typically have poor temperature resistance. 

B. Polymeric Urea [Benzene, diethenyl-, polymer with ethenylbenzene, [[[[(1 methylethyl)amino]carbonyt]amino]methyl] deriv.] A 10.0-g. portion of benzylamine polymer beads prepared as in Part A and 125 ml. of tetrahydrofuran (Note 6) are combined in a 300-ml., three-necked, round-bottomed flask equipped with a magnetic stirrer, a dropping funnel, and a condenser fitted with a gas-inlet tube A nitrogen atmosphere is established in the system, and the slurry is stirred while 1.35 g. (0.0159 mole) of isopropyl isocyanate [Propane, 2-isocyanato-] is added. This causes an exothermic reaction, which subsides after about 20 minutes. The mixture is then stirred at room temperature for 22 hours and at reflux for an additional 4 hours. The beads are collected by filtration, washed with 150-ml. portions of tetrahydrofuran (Note 6) and methanol, and dried under reduced pressure over calcium chloride to yield 9.09 g, of the isopropyl urea polymer. 

The same group recently reported that the TBB defects can be brought below the nuclear magnetic resonance (NMR) detection limit by employing similar polymerization conditions (i-BuOK in THF at room temperature) in the synthesis of naphthyl-substituted PPVs 51-53 [112]. Although the absorption and PL spectra of all three polymers are similar, the EL can be finely tuned between 486 nm (for 52) and 542 nm (for 53). The external QE (studied for ITO/PEDOT/polymer/Ba/Al device) is also sensitive to the substituents pattern in the naphthyl pendant group 0.08% for 51, 0.02% for 52, and 0.54% for 53. 

Polymerization Method. To a solution of 5.18 mmole of HFB or PFB and 5.18 mmole of the appropriate bisphenol or bisthiophenol in 20 ml of solvent was added 22.4 mmole anhydrous of K2CO3 and 1.43 mmole of 18-crown-6 ether. The magnetically stirred, heterogenous mixture was heated in an oil bath and maintained under N2. Upon cooling to room temperature, the mixture was slowly poured into ca. 150 ml of methanol and was vigorously stirred. The filtered solids were washed three times in a blender with 300-ml portions of distilled water. The solids were air dried and subsequently placed in a vacuum oven (80 ) for 24 hr. Where soluble, the polymers obtained were characterized by IR and PMR analysis. Elemental analyses for all polymers were satisfactory. Polymer solubility was determined in THF, DMF, dioxane, toluene, m-cresol, chloroform, and sulfuric acid. The percent insoluble polymer was determined gravimetrically. Inherent viscosities of soluble polymers were determined in ca. 0.5% wt. solutions in either chloroform or THF. 

Figure 3 Molecular relaxivities of liposomes with different Gd-containing membranotropic chelators. Liposomes (egg lecithin cholesterol chelator = 72 25 3) were prepared by consecutive extrusion of lipid suspension in HEPES buffered saline, pH 7.4, through the set of polycarbonate filters with pore size of 0.6, 0.4, and 0.2 mm. Liposome final size was between 205 and 225 nm. Gd content determination was performed by Galbraith Laboratories, Inc. The relaxation parameters of all preparations were measured at room temperature using a 5-MHz RADX nuclear magnetic resonance proton spin analyzer. The relaxivity of liposomes with polymeric chelators is noticeably greater because of the larger number of Gd atoms bound to a single lipid residue [16].

The first three components were mixed at room temperature and heated at 65°C In a 250 ml round bottom flask equipped with a magnetic stirring bar, reflux condenser and Na blanket. The AIBN was then added to start the reaction. Monitoring of the unreacted free monomers (butyl acrylate and comonomer) was done by GLPC. Additional 10 mg amounts of AIBN were added as needed. The temperature was also Increased to 75 C to finish the polymerization. Host of the reactions took longer than 24 h to reduce the free monomer below 0.7%. A control BA homopolymer and copolymers with butoxymethylacrylamide (BNMA), 2 (R = Et AEP), acrylamidoacetaldehyde dimethyl acetal (AADMA), and N-ethyl-1 (Et-ABDA, 13) were prepared In this way. 

Polymerization of Butadiene in Presence of PVC. Et2AlCl-Cobalt Compound Catalyst. A suspension of 20 grams of PVC and 18.7 mg (0.03 mmole) of cobalt(II) stearate in 300 ml of chlorobenzene in a three-necked flask equipped with a reflux condenser, Teflon-coated magnetic stirring bar, thermometer, and gas inlet and outlet was stirred at room temperature for 1 hour while nitrogen was bubbled through. The... 

Disordered low-dimensional C60 polymers also show interesting magnetic properties. In particular, Makarova et al. [16] reported that rhombohedral C60 polymerized at high temperatures near 6 GPa showed signs of weak ferromagnetism (nonlinear susceptibility and magnetic hysteresis loops, as shown in Fig. 16) at temperatures well exceeding room temperature. This has been verified... 

Under a stream of nitrogen charge a single-necked round-bottomed flask (100 mL) with a magnetic stirrer bar, polymeric Hiinig s basec (4.55 g), and dry dioxane (11 mL). Stir the mixture for 30 min, then add a solution of crude aminal 8 (1.1 g, 2.6 mmol) in dry dioxane (23 mL) followed by thionyl chloride (0.8 mL). Stir the mixture at room temperature under nitrogen for 3 h. Filter off the insoluable polymeric base and evaporate the filtrate in vacuo to obtain the crude halide. 

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