Evaporation from solution

Solvent Evaporation from Solutions of Thermoplastic Polymers. A solution of a copolymer of vinyl chloride (chloroethene) [75-01-4] C2H2CI, vinyl acetate (acetic acid ethenyl ester) [108-05-4] and a hydroxy-functional vinyl monomer having a number average molecular... 

It has been reported that the evaporation of a chloroform solution of peroxybenzoic acid (perbenzoic add) according to the directions published in this series1 has resulted in a heavy explosion. Hence suitable precautions should be observed in carrying out solvent evaporations from solutions of peroxybenzoic acid. Such precautions and other useful information have been given elsewhere in this series.2... 

Various techniques have been used to prepare single crystals of polydiacetylene. Bulk crystals obtained by conventional crystallization procedures (e.g., slow cooling or evaporation from solution) tend to be riddled with defects such as grain boundaries or stacking faults, and are not suitable for optical applications. The LB technique, on the other hand, has been... 

The most generally used solution-based method to synthesize cocrystals is slow evaporation from solutions with equimolar or stoichiometric concentrations of cocrystal components.f Solvo-thermal methods are also reported in the literature, although less frequently. ° In this method, heat is used to dissolve stoichiometric amounts of both components, the solution is cooled, and the cocrystals are then allowed to nucleate and grow. These processes, however, suffer from the risk of crystallizing the single component phases, thereby reducing the possibility of isolating the multiple component crystalline phase. As a result... 

Fig. 4.5. MAC mode AFM topographical images in air of (A1 and A2) clean HOPG electrode surface (B1 and B2) thin-film dsDNA-biosensor surface, prepared onto HOPG by 3 min free adsorption from a solution of 60 /xg ml dsDNA in pH 4.5 0.1 M acetate buffer electrolyte (Cl and C2) thick-film dsDNA-biosensor surface, prepared onto HOPG by evaporation from solution of 37.5 /xgml dsDNA in pH 4.5 0.1 M acetate buffer electrolyte (Al, B1 and Cl) two-dimensional view 1 pm x 1 pm seem size and (A2, B2 emd C2) three-dimensional view 500 nm X 500 nm scan size. (Reproduced from Ref. [91] with permission from Elsevier.)...

A new method for forming 2, 3 -cyclic phosphates of ribonucleosides using very mild conditions has been described. It may also be used to introduce a terminal cyclic phosphate in protected oligonucleotides. When 2, 3 -cyclic AMP is evaporated from solution at alktiline pH in the presence of aliphatic diamines, and maintained dry at elevated temperatures, polymerization occurs. Oligomers up to the hexanucleotide are formed, preferentially with 3 ->5 internucleotidic links. This may have been an important process in prebiotic synthesis. 

Catalysts were deposited on the char particles by evaporation from solution. Catalyst concentrations were 5 wt % metal. Catalyst distribution on the char was examined by electron microprobe and scanning electron microscopy. 

Disposable IR cards with a thin polymer film window are available for the qualitative analysis of liquids. (These cards were originally manufactured by 3M , but are now available from International Crystal Laboratories, Garfield, NJ, and other suppliers.) Two polymer substrates are available polytetrafluoroethylene for the 4000-1300 wavenumber region and polyethylene for the lower wavenumber region. The absorption spectra for these two materials are displayed in Fig. 4.19(b) and (c). A thin film can be deposited onto the polymer window by evaporation from solution or by smearing the liquid onto the polymer. A major advantage of these cards is that the polymer films do not dissolve in water therefore... 

Preparation.—ITie oxide is prepared by heating the nitrate, sulphate, oxalate, hydroxide, basic carbonate or other salt of beryllium containing a volatile acid radical, and even the chloride, bromide and iodide yield practically all of their metal as oxide when evaporated from solution and heated. By evapwat-ing to dryness a mixed solution of beryllium chloride and ammonium chloride and heating in air, an oxide so light and feathery IS produced that it is difficult to retain it in the containing vessel. 

This type of crystallisation was first suggested by Storks in 1938. He made films of gutta percha 27 nm thick by evaporation from solution. Electron diffraction showed that the films were composed of large crystallites with the chain axes normal to the plane of the film. The only possibility was that the chains folded back and forth upon themselves, so that adjacent segments were parallel and in crystal register. 

Chart LL Useful internal standards for analysis of solution-phase combinatorial libraries. 2,5-dimethylfuran (DMFu, 1) and hexamethyldisiloxane (HMDS, 2) are volatile standards that can easily be evaporated from solution-phase samples after analysis. 1,4-bis (trimethylsilyl)benzene (BTMSB, 3) is stable in DMSO for up to one month and is transparent in HPLC-UV and MS analyses. 

In order to verify the possibility of the contribution of these reactions to the change in the mechanical properties, some quantities of 4,4 -diamino diphenyl methane (MDA) were incorporated into the polymeric material, so to obtain an equivalent quantity of -NH2 groups equal to 0.02 g / 100 g of a linear PU (equal to the excess initial concentration of -NCO groups corresponding to I = 110). Thin films of PUs with MDA about 0.5 mm thick were obtained by evaporation from solution at 60°C as described elsewhere [17]. 

Larger-Scale Methods, On a large scale, these evaporation methods can also be applied to standard-sized glassware. Solvents can be evaporated from solutions... 

FIGURE 7.27 Rate of evaporation from solution. When a solution forms, the presence of the solute particles reduces the rate of evaporation of the solvent, thm decreasing the equilibrium vapor pressure. 

This effect may be interpreted by assuming different equilibrium proportions of the syn and anti conformations in the solid and solution states of the polymer. We have so far been unable to detect this change by C NMR within the limited precision of intensity measurements ( 10%). Surprisingly the isotactic polymer, as prepared by evaporation from solution, is amorphous and only crystallises to a slight extent on annealing at 100 °C. The observed activation energy is consistent with the barrier to rotation about the peptide link known from other work [8]. 

Polar polymers also tend to be monopolar when dried from aqueous solutions, or when obtained in a flat solid layer through evaporation from solution in an organic solvent. Examples are dextran, various proteins (van Oss 1994 van Oss et al, 1995b) as well as polymethyl methacrylate (van Oss 1994). Dextran is a polymer of glucose, which therefore contains many OH-groups. Nonetheless only electron-donating activity is found on dry layers of... 

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