Amorphous foaming

A stirred suspension of diethylenetriaminepentaacetic acid dianhydride (10.8 g, 0.030 mole) in 100 ml of isopropanol was treated with 2-methoxyethylamine (5.0 g, 0.067 mole). The entire mixture was heated at 50°C for 4 hours in a water bath. The pale yellow solution was filtered through a medium porosity sintered glass funnel to remove undissolved impurities, and the filtrate was taken to dryness under reduced pressure. The resulting amorphous foam was dried (vacuum desiccator) at ambient temperature for 18 hours. The yield of the N,N"-bis[N-(2-methoxyethyl)-carbamoylmethyl]diethylenetriamine-N,N, N"-triacetic acid 14.4 g (93.5%). 

A mixture consisting of the Step 7 product (0.74 mmol), 4-pyrrolidinopyridine (0.09 mmol), and 927 jxl n-butyl chloroformate dissolved in 6 ml pyridine was stirred 2 days at ambient temperature, then concentrated. The residue was dissolved in CH2C12, washed with a 10% solution of citric acid and with water, dried with Na2S04, and concentrated. The residue was purified by chromatography using CH2Cl2/methyl alcohol, 20 1, and 470 mg of product isolated as a slightly yellow amorphous foam. 

The original synthesis of ABT-839 (2) efficiently provided material for early studies and provided the flexibility to vary the sidechains in order to study SAR. However, e route required at least three chronmtographic separations, which prohibited synthesis of kilogram quantities of material. The penultimate intermediate was purified by column chromatography prior to the final ester hydrolysis and the final product was isolated as an amorphous foam. We were seeking an efficient process that addressed the concerns of purification of intermediates, allowed for isolation of a crystalline final product and could be used to synthesize kilogram quantities of material. 

Pure amorphous polymers, being homogeneous materials, are transparent. Atactic polystyrene is a good example. The crystalline syndiotactic form is not transparent. Alack of transparency does not necessarily indicate crystallinity, however. It can also be caused by inorganic fillers, pigments, gas bubbles (as in a foam), a second polymer phase, etc. 

Polystyrene. Polystyrene [9003-53-6] is a thermoplastic prepared by the polymerization of styrene, primarily the suspension or bulk processes. Polystyrene is a linear polymer that is atactic, amorphous, inert to acids and alkahes, but attacked by aromatic solvents and chlorinated hydrocarbons such as dry cleaning fluids. It is clear but yellows and crazes on outdoor exposure when attacked by uv light. It is britde and does not accept plasticizers, though mbber can be compounded with it to raise the impact strength, ie, high impact polystyrene (HIPS). Its principal use in building products is as a foamed plastic (see Eoamed plastics). The foams are used for interior trim, door and window frames, cabinetry, and, in the low density expanded form, for insulation (see Styrene plastics). 

Treatment of ceUulose with acids results in preferential hydrolysis in the more accessible amorphous regions and produces a product known as microcrystalline ceUulose (MCC). MCC is used to prepare fat-free or reduced-fat food products, to strengthen and stabilize food foams, as a tableting aid, and as a noncalotic bulking agent for dietetic foods. It has GRAS status. 

Ultem PEI resins are amber and amorphous, with heat-distortion temperatures similar to polyethersulfone resins. Ultem resins exhibit high modulus and ate stiff yet ductile. Light transmission is low. In spite of the high use temperature, they are processible by injection mol ding, stmctural foam mol ding, or extmsion techniques at moderate pressures between 340 and 425°C. They are inherently flame retardant and generate Httie smoke dimensional stabiUties are excellent. Large flat parts such as circuit boards or hard disks for computers can be injection-molded to maintain critical dimensions. 

Experiments pertaining to a new system for the application of bromine to flame retardant polypropylene and foamed polystyrene are described. The FR compound, ammonium bromide, is formed in the amorphous regions of the polymer phase by the interaction of bromine sorbed on the polymer and ammonia, sorbed subsequently. Gaseous nitrogen which is also produced, expands and brings about the rearrangement of the chains to produce a porous structure. The ammonium bromide produced is finely divided and imparts FR properties to the polymer. 

Carbon electrodes are commercially available in many forms. These include plates, foams, felts, cloths, fibers, spherical and other particles suitable for beds or powders. Graphite or amorphous carbons exhibit quite different performances. Porosity, surface area and pretreatment are important variables to be considered in designing carbon electrodes. 

Foam formation was possible only in the amorphous high Tg polyimides however, the volume fraction of voids does not correspond to the volume fraction of propylene oxide in the initial copolymer. A decrease in the volume fraction of voids incorporated into the matrix in comparison to the initial volume fraction of the propylene oxide in the copolymer can be understood by consid-... 

The ESI domains in ESI/LDPE blends are 0.1 to 2.8 pm in length (71). As the ESI (S series with 70% styrene) used was amorphous, the use of ESI reduced the overall crystallinity of the blend. However, with 25% ESI, the compressive stress at 25% compression of the foam is unchanged. Eor ESI, the processing window is wider, and the cell structure is slightly finer than for the equivalent LDPE foam. 

The styrene content affects the crystallinity of ESI (131) for >50% styrene the copolymers are amorphous. As the styrene content is increased from 50 to 70% styrene the Tg increases from -15 °C to 20 °C. Low density foams were made (8) from a blend of 50% of various ESI polymers, 33% of EVA and 17% of azodicarbonamide blowing agent. Thermal analysis showed that the blends, with an ESI having approximately 70% styrene, had a Tg in the range 22 to 30 °C. Dynamic mechanical thermal analysis (DMTA) traces (see Section 5.1) show that these blends... 

Figure 12 shows the temperature variation of the in-phase Young s modulus E of an EVA foam (Verdejo, unpublished). E falls as the amorphous phase goes through a glass transition close to -10 °C, then again as the crystalline phase melts at 80 °C. The peaks in tan S at these temperatures are labelled a and p. 

An investigation was carried out on concrete containing up to 30% of PE foam waste in order to optimise the thermal conductivity of the concrete. An amorphous aggregate of ash-slag waste was utilised to decrease the thermal conductivity of the concrete. 5 refs. 

Fig. 4a, b. Scanning electron photomicrographs of amorphous poly(L-lactic acid) foams a 92% porosity and 30 pm median pore diameter b and 91% porosity and 94 pm median pore diameter. Prepared by a solvent-casting and particulate-leaching method [32] using 90 wt% sieved sodium chloride particles of size range between 0-53 pm and 106-150 pm, respectively... 

The solid phase resulting from this reaction typically forms a white precipitate, which on account of its low density often forms impressive masses of white foam where the water, from which it is precipitating, is subjected to turbulent eddies. Generally, this white precipitate is X-ray amorphous, although if it is allowed to settle for periods in excess of six months, crystalline forms of Al(OH)3, most notably gibbsite, are... 

Dimethyl selenide, (CH3)2Se.—An intimate mixture of selenium and amorphous phosphorus (5 2) is heated, and the black mass powdered and heated in a retort with concentrated sodium hydroxide and potassium methyl sulphate. The mixture foams and a yellow liquid distils over. This is separated from the water and fractionated to remove dimethyl diselenide, which is present in small quantity. 

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