Dimethyl formamide viscosity

The intrinsic viscosity of poly(7-benzyl-L-glutamate) (Mq = 219) shows such a strong molecular weight dependence in dimethyl formamide that the polymer was suspected to exist as a helix which approximates a prolate ellipsoid of revolution in its hydrodynamic behaviorf ... 

The physical properties of finish removers vary considerably due to the diverse uses and requirements of the removers. Finish removers can be grouped by the principal ingredient of the formula, method of appHcation, method of removal, chemical base, viscosity, or hazardous classification. Except for method of apphcation, a paint remover formulation usually has one aspect of each group, by which it can be used for one or more appHcations. A Hst of the most common organic solvents used in finish removers has been compiled (3). Many are mentioned throughout this article others include ethyl lactate [97-64-3] propylene carbonate [108-32-7] furfural alcohol [98-01-1/, dimethyl formamide [68-12-2] tetrahydrofuran [109-99-9] methyl amyl ketone [110-43-0] dipropylene glycol methyl ether [34590-94-8] and Exxate 600, a trade name of Exxon Chemicals. 

Intrinsic Viscosity Measurements were made by standard techniques in dimethyl formamide (DMF) at 30 C. Weight average molecular weights were calculated from the following relationship ... 

Reduced viscosity = (t solution-t solvent)/t solvent for 1% solution in dimethyl formamide at 25° C. 

Fig. 3. Intrinsic viscosity-molecular weight relationship of poly-7-benzyl-L-glutamates. The open circles represent the randomly coiled form and other symbols the a-helical form. The line of steeper slope is a plot of Simha s equation. Abbreviations dichloroacetic acid, DCA chloroform saturated with formamide, C-F dimethyl formamide, DMF light scattering, L.S. weight-average molecular weight, A/m. Reproduced from Doty et al. (1956).

Systematic application of hydrodynamic and light-scattering methods has been made in conjunction with optical rotatory studies upon poly-e-Y-car-bobenzoxy-L-lysine (Applequist and Doty, 1961 Daniel and Katchalski, 1960, 1961) and poly-L-lysine (Applequist and Doty, 1961). Poly-e-Y-car-bobenzoxy-L-lysine in dimethyl formamide displays light scattering, viscosity, and flow birefringence behavior that is consistent with a predomi-... 

The polyamic acids were prepared from 3,3 ,4,4-benzophenone dianhydride (sublimed) and 2,3,5,6-tetramethyl-l,4-phenylene diamine in Cold Label N,N-dimethyl formamide (DMF). All chemicals were obtained from Aldrich. A solution of the anhydride was added over 30 minutes to a solution of the amine with stirring under N2 at room temperature at a net concentration of 15% solids. In general, a slight (1%) excess of the anhydride was needed to give maximum viscosity. 

Studies on the dilute solution behavior of sulfonated ionomers have shown these polymers to exhibit unusual viscosity behavior in solvents of low polarity. These results have been interpreted as arising from strong ion pair associations in low polarity diluents. Solvents of higher polarity, such as dimethyl sulfoxide and dimethyl formamide induce classic polyelectrolyte behavior in sulfonate ionomers even at very low sulfonate levels. To a first approximation these two behaviors, ion pair interactions or polyelectrolyte behavior, are a consequence of solvent polarity. Intramolecular association of Lightly Sulfonated Polystyrene (S-PS) results in a reduced viscosity for the ionomer less than that of polystyrene precursor at low polymer levels. Inter-association enhances the reduced viscosity of the ionomer at higher polymer concentrations. Isolation of the intra- and inter-associated species of S-PS has been attempted (via freeze drying). A comparison of selected properties reveals significant differences for these two conformations. 

Few studies have been conducted heretofore on sulfonated ionomers in solvents which can be considered relatively polar, as defined by a high dielectric constant. A recent study (13) on acrylonitrile-methallyl sulfonate copolymers in dimethyl-formamide is a notable exception. S-PS is readily soluble in a wide variety of solvents, some of them exhibiting rather high values of dielectric constant, such as dimethylformamide (DMF) or dimethylsulfoxide (DMSO). The reduced viscosity-concentration behavior of sulfonated polystyrene is markedly different in polar solvents from that in nonpolar-solvent systems. Typically there is a marked upsweep in reduced viscosity at low polymer concentrations and clearly a manifestation of classic polyelectrolyte behavior. ( 7)... 

Dilute Solution Viscosity Polymer dilute solution viscosity was measured at a concentration of 0.400g/dl of N,N-dimethyl-formamide[DMF, contained 0.05% n-propyliodide stabilizer16] at 25°C 0.1°C using an Ostwald-type viscometer. 

Materials. The copolyether-urethane-ureas were prepared from polypropylene glycol, methylene bis(4-phenylisocyanate), and ethylenediamine using a modified solution polymerization technique (7). The polypropylene glycols used had molecular weights of 700, 1000, and 2000 the resulting copolymers were coded PEUU 700, PEUU 1000, and PEUU 2000. Inherent viscosities in N,iV-dimethyl-formamide at 30°C and 0.5% concentrations were 0.47, 0.65, and 0.50, respectively. 

Figure 9-26. A plot according to Equation (9-151) of the molar mass dependence of the intrinsic viscosity of poly(7-l>enzyl-L-glutamate) in dichloroacetic acid (DCA) and dimethyl formamide (DMF) at 25°C. Coils occur in DCA and helices occur in DMF (according to P. Rohrer and H.-G. Elias).

Pingping et al. examined the viscosity behaviour in PCL/PVC blends (50 50 w/w) in dilute solutions (<0.02 g cm" ) in several solvents - 1,2-dichloroethane (DCE), N,N-dimethyl formamide (DMF) and tetrahydrofuran (THF) [97]. In each case the intrinsic viscosity (the limiting values of r p c at zero concentration) of the PCL used was about 0.2 dl g and values of r]gp/c varied Httle with concentration. Intrinsic viscosities of PVC in DCE, THF and DMF were 1.7,1.0 and 0.76 dl g respectively in THF and DMF values of rj p/c increased with PVC concentration but in DCE decreased with increasing polymer concentration. In the three solvents the blends had intermediate viscosity behaviour variations of 77sp/c with concentration were slight and in DCE the dependence was non-linear. The authors defined ideal solution behaviour for a binary mixture of polymers A and B as one for which the relation... 

The traditional technique for sulphonylation with sulphonyl chlorides uses at least one mole of Friedel-Crafts halide per mole of sulphonyl chloride and it was realised that this would lead to difficulties in isolating polymers free from inorganic contaminants. However, the preparation of monomeric sulphones using catalytic quantities of FeCl had been reported in a war-time German patent [12] and we applied this procedure to reactions (1). Polymers of high molecular weight (reduced viscosity, RV, up to 1.2 for 1% solutions of polymer in dimethyl formamide at 25 C) were obtained... 

Wet spinning also involves pumping a solution to the spinneret. Now, however, the polymer is precipitated in an immiscible liquid. Polyacrylonitrile in dimethyl formamide, for example, can be precipitated by passing a jet of the solution through a bath of water, which is miscible with the solvent but causes the polymer to coagulate. Cellulose triacetate can be wet-spun from a methylene chloride-alcohol mixture into a toluene bath, where it precipitates. In other fibers, the precipitation can involve a chemical reaction. Viscose rayon is made by regenerating cellulose from a solution of cellulose xanthate. 

Thermoplastic starches find use mainly in water soluble compostable foams, expanded trays, shape molded parts, and expanded layers as a replacement for polystyrene. TPS products with different viscosity, water solubility, and water absorption have been prepared by altering the moisture/plasticizer content, amylose/amylopectin ratio of raw material, and the temperature and pressure in the extruder (Mohanty et al, 2000). Several studies have focused on the plasticization of TPS using glycerol (Forssell et al, 1997), sorbitol (Gaudin et al, 1999), urea, formamide (Ma et al, 2004), dimethyl sulfoxide (Nakamura and Tobolsky, 1967), and low molecular weight sugars (Kalichevsky et al, 1993). Plasticizers can increase the flexibility and processibility of TPS. 

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