Dimethylacetamide solutions

Callais PA (1986) Derivatization and Characterization of Cellulose in Lithium Chloride and NdV-Dimethylacetamide Solutions. Ph.D. Thesis, University of Southern Mississippi, USA... 

Rhodium trichloride oxidises ethylene in dimethylacetamide solution to a... 

Infrared Spectra. Films of the polymer samples were prepared by casting from a DMSO or a dimethylacetamide solution unto a salt plate. These were then examined for their infrared spectral properties in a Beckman AccuLab A spectrophotometer. Basically, as the degree of substitution increased, the OH peak (3300-3A00 cm-- -) diminshed in intensity and the C=0 peak (1710 cm-- -) increased in intensity-. Peaks due to the NH (3120-31A0 cm-l) and phenyl groups (3030-3050 cm-l) also developed as the substitution increased and the relative intensity of the aliphatic CH (backbone chain) (2910-29A0 cm-l) decreased at the same time. Some of these results are summarized in Table I where the ratios of the C = O/OH and phenyl/aliphatic CH peaks are reported for various degrees of substitution. 

In a typical experiment the isocyanate (0.006 moles) was reacted with 1.5 g of the polysaccharide in 150 ml of a 5% LiCl/ N,N-dimethylacetamide solution at 90°C under nitrogen for two hours. The appearance of a strong infrared absorbance at 1705 cm l was an indication of carbamate formation. The derivatized polymer was isolated as a white powder by precipitation of the reaction solution into a nonsolvent such as methanol. Alternatively thin films were cast directly from solution the lithium salt could be removed by rinsing with acetone. Figure 1 illustrates the reaction of cellulose with phenyl isocyanate. 

In a typical example (Figure 2), the 2,2-dichloropropionate ester of chitin was prepared by reacting 1.0 g of chitin dissolved in 100 ml of a 5% LiCl/N,N-dimethylacetamide solution with 0.006 moles of 2,2-dichloropropionyl chloride at 140°C for three hours. The product was isolated by precipitation into methanol. 

Viscosity data are reported in Table I for a number of the polysaccharide derivatives in 5% LiCl/N,N-dimethylacetamide solutions. At low concentrations of polymers, an upward curvature in the DSp/c (reduced viscosity) vs c (concentration) plot was observed. Additionally, nonlinear increases in solvent viscosity were observed for increased lithium ion concentrations in the absence of polymer. Therefore, reduced viscosities at 0.25 dl/g are reported. 

Cobalt(II) chloride was dissolved in poly(amide acid)/ N,N-dimethylacetamide solutions. Solvent cast films were prepared and subsequently dried and cured in static air, forced air or inert gas ovens with controlled humidity. The resulting structures contain a near surface gradient of cobalt oxide and also residual cobalt(II) chloride dispersed throughout the bul)c of the film. Two properties of these films, surface resistivity and bullc thermal stability, are substantially reduced compared with the nonmodified condensation polyimide films. In an attempt to recover the high thermal stability characteristic of polyimide films but retain the decreased surface resistivity solvent extraction of the thermally imidized films has been pursued. 

The third method of dissolution is based on the mild chlorination of chemically modified wood according to Sakata and Morita (13) (Postchlorination method). Chlorination, in fact, resulted in enhanced solubility of chemically modified wood in solvents, including phenol. For example, chlorinated cyanoethylated wood does not only dissolve in cresol even at room temperature, but it also dissolves (under heating) in resorcinol, phenol and a LiCl-dimethylacetamide solution. 

A 10 wt% dimethylacetamide solution of the step 2 product (1 g) was cast on a glass Petri dish, heated to 200°C for 1 hour and then further heated to 300°C for an additional hour and 0.09 g of product isolated. 

In N,N-dimethylacetamide solution the reduction by hydrogen of ruthenium(HI) chloride is claimed to produce ruthenium(I) complexes which hydrogenate ethylene, maleic and fumaric adds. The complexes are thought to be dimeric but their precise structures are unknown. Interestingly, these d1 ruthenium(I) complexes are believed to activate hydrogen by oxidative addition whereas heterolytic cleavage of hydrogen occurs with most ruthenium catalysts (equation 19). 

Acetylrhodium(III) tetraphenylporphyrin was formed on warming N,N-dimethylacetamide solutions of RhH(TPP) [319]. Obviously, an acetyl group had been abstracted from a solvent molecule. 

When chemically modified woods are chlorinated, their solubility in solvents is tremendously enhanced. For example, at room temperature cyanoethylated wood can dissolve in o-cresol by only 9.25%. However, once chlorinated, it can dissolve almost completely in the same solvent at room temperature. The chlorinated-cyanoethylated wood can also dissolve in resorcinol, phenol, and an LiCl-dimethylacetamide solution under heating. 

The phthalocyanine complexes of manganese have been studied for many years ° The most recent work has established the formation of an rf dioxygen complex on oxygenation of [Mn(Pc)] in N,N-dimethylacetamide solution and a similar result has been obtained for a tetra-sulphonated phthalocyanine derivative The porphyrin complex Mn(TPP)02 was assigned an rf structure on the basis of E.P.R. data and this assignment has recently been supported by infra-red data using 02 Schiff base complexes of Mn(II) were reported to form dinuclear rf complexes on oxygenation in... 

Flg. lOa-c. Chain unfolding and cis to Irons isomoization of polyamide (d) in iV,iV-dimethylacetamide solution (0.31 g/ dl) [2. The oscUlogianis illustrate changes of light scattering intensity (a,c) at 514 nm and optical absorption at 514 nm (b) during and after 20 ns flash of 530 nm light. Traces a and b polyamide (6) trace c model compound... 

The Mass spectral curing studies were done by heating each sample of polymer in the DIP consecutively at 100°C, 200°C, and 350°C for 1 hour each. The extent of cure at 200°C was estimated by taking the ratio of the area for the peak at 200°C in the TIC (or the ion chromatogram of water or isobutene) to the combined area of the peaks at 200°C and 350°C. The samples for the IR curing study were spun from dimethylacetamide solutions of the polyamic acid or its esters onto NaCl... 

Fibers have been wet spun from dimethylacetamide solution, and a deep gold woven cloth has been made from this fiber by Celanese. The cloth is said to be more comfortable than cotton (due to high moisture retention) and has greater flame resistance than Nomex (oxygen index of 29% for PBI compared to 17% for Nomex). The U.S. Air Force has tested flight suits of PBI and found them superior to other materials. 

Poly (S-leucinato-AT, 0) cobalt (III) -u- [3,3 -dithiobis (2,4-pentanedion-ato-0,0 )]).—Initially, 1.7460 g disulfur dichloride (12.93 mmol) in 6 mL dry dichloroethane was added dropwise to 5.0088 g Co(leu)(acac)2 (12.93 mmol) in 20 mL dimethylacetamide (DMAC) with 0.7095 g sodium carbonate (6.69 mmol) as a slurry in the dimethylacetamide solution under argon and with vigorous stirring. The mixture was stirred for 24 - 36 h and then precipitated with diethyl ether. Alternatively, the solvent was removed in vacuo at 45 C. The product was collected on a fritted funnel, washed with water, and dried in vacuo at lOO C yield, 5.5 g 95%. The polymer was fractionated (three times) by a DMAC/acetone or dimethyl sulfoxide/acetone solvent/nonsolvent precipitation to remove low molecular-weight material. 

The dimer [RhCl(C8Hi4)2]2 in dimethylacetamide solution also catalyses oxidation, of carbon monoxide, of the cyclo-octene ligand, and of the dimethylacetamide. An oxygen complex of rhodium(ii) appears, from preliminary e.s.r. results, to be a likely intermediate.Rhodium trichloride itself can also catalyse oxidation of carbon monoxide. ... 

Polymer Synthesis and Film Processing. T-AZODIOL and TDI or PDI in equivalent molar ratios were reacted in dimethylacetamide solution at 85°C for 20 - 30 min under nitrogen atmosphere to prepare T-polymer or T-polymer 2, respectively. Similarly, L-polymer and L-polymer 2 were prepared from AZODIOL with TDI and PDI, respectively. Molecular structures of these polymers are shown in Figure 2. A spin-casting technique was employed to prepare thin films for SHG measurements. 

After drying for 15 h in vacuo, polyurethanes were compression moulded at temperatures between 100 and 200 C and at a nominal load of either 8 or 12 tons. Biomer" was solvent cast in 3 layers directly from the 30% dimethylacetamide solution supplied and the sheets were dried at 40 C in a flow of dry nitrogen for 7 days. The flat sheets had dimensions of 60 mm x 100 mm and were 1 mm thick. They were cut into several pieces or punched into dumbbells 3 cm in length. The straight (testing) area of the dumbbell was 13 nun x 4 mm. All samples showed no birefringence under cross polarizers, indicating that there was no detectable residual stress. 

The polymerization reaction takes place in a homogeneous dimethylacetamide solution, with catalytic amounts of PdCl2(PPh3)2 and an HBr scavenger. The carbonylation polycondensation proceeds rapidly at 115 C and is almost complete in 1.5 hours. This reaction was also used to prepare many aromatic-aliphatic polyamides from corresponding aliphatic diamines with aromatic dibromides. 

McCormick C.L., Callais P.A., Derivatization of ceUulose in lithium chloride and N,N-dimethylacetamide solutions. Polymer, 28,1987, 2317-2323. 

Zhang Z.B., McCormick C.L., Structopendant unsaturated cellulose esters via acylation in homogeneous Uthium chloride/ A/A/-dimethylacetamide solutions, J. Appl. Polym. Sci., 66, 1997,293-305. 

Preparation of Antibacterial O-Carboxymethylated Chitosan/Cellulose Blend Film from LiCL/yV,N-DiMETHYLACETAMiDE Solution (Li et al. 2002)... 

Fibers were spun from poly(amic acid)/dimethylacetamide solutions and the resultant poly(amic acid) fibers were then thermally converted to polyimide fibers under sufficient tension. The polyimide fiber was finally heat treated at 525-575°C. 

---