Imide concentration

According to varying conditions (temperature, reaction time, imide concentration, stabilizer etc.) the base catalysed polymerization may lead to products of a very wide range of molecular weights andtypesof distribution. It is possible to prepare without difficulty polymers ranging from a degree... 

The final molecular weight of the polyamide may be reduced, if desired, not only by increased initial imide concentrations (30, 50). or by... 

Toxicity. The estimated minimum lethal dose is 5 g. Toxic effects are usually associated with plasma Wdesmethylmethsux-imide concentrations of more than 40 pg/ml. 

Figure 4. Plot of imide concentration versus temperature for Toray Photoneece, BTDA/ODA polyamic acid, and an ethyl ester of PMDA/ODA.

An alternative method to obtain a negative inside Donnan potential across the vesicular membrane involves preparation of the vesicles as in the first case (i.e., in glucose solution) and the addition of polyethylene imide (PEI+) instead of sodium polyacrylate after incubation with alamethicin. The polyethylene imide concentrations, as well as the polypeptide to lipid ratio, were approximately equivalent to the polyacrylate. 

The evolution of viscosity with regards to blend composition is shown in Figure 4.3. Viscosity was shown to correspond well with the three types of typical phase stmeture, namely phase dispersion, bicontinuous and phase-inversion morphology in thermoplastic-modified thermoset systems. Before phase separation, the homogeneous mixture behaved as a semidilute polymer solution, and the viscosity increased in line with the poly(ether imide) concentration. However, on phase decomposition, tj was shown to increase or decrease abmptly, depending on the morphology variation. 

Saccharin (imide of o-sulphobenzoic acid). Upon oxidising o toluene-sulphonamide with potassium permanganate in alkaline solution, the sodium salt of o-sulphonamidobenzoic acid is formed, which upon acidifying with concentrated hydrochloric acid or warming passes spontaneously into the cyclic imide of o-sulphobenzoic acid or saccharin ... 

When acetone is condensed with ethyl cyanoacetate in the presence of a solution of anhydrous ammonia in absolute alcohol at —5°, the ammonium salt of the dicyano-imlde (I) is precipitated. Upon dissolving this salt in water and adding excess of concentrated hydrochloric acid, the crystalline dicyano-imide (II) is obtained. Hydrolysis of the last-named with strong sulphuric acid affords p p dimethylglutaric acid (III). 

Polymers in Solution. Polyacrylamide is soluble in water at all concentrations, temperatures, and pH values. An extrapolated theta temperature in water is approximately —40° C (17). Insoluble gel fractions are sometimes obtained owing to cross-link formation between chains or to the formation of imide groups along the polymer chains (18). In very dilute solution, polyacrylamide exists as unassociated coils which can have an eUipsoidal or beanlike stmcture (19). Large aggregates of polymer chains have been observed in hydrolyzed polyacrylamides (20) and in copolymers containing a small amount of hydrophobic groups (21). 

After about 12 hours, the ammonium salt of the imide which has precipitated is removed by filtration (Note 3), washed on a Buchner funnel with about 200 ml. of ether and air-dried. It is dissolved in the minimum amount (about 800 ml.) of boding water, and the solution is made acid to Congo red paper with concentrated hydrochloric acid. The free imide precipitates immediately and forms a wlrite slurry which is cooled in an ice bath. The imide is collected on a Buchner funnel and dried at 100° in an oven, or in a vacuum desiccator. The yield is 266-287 g. (65-70%), m.p. 187-191° (Note 4). 

Polydithiazoles Polyoxadiazoles Polyamidines Pyrolyzed polyacrylonitrile Polyvinyl isocyanate ladder polymer Polyamide-imide Polysulfone Decompose at 525°C (977°F) soluble in concentrated sulfuric acid. Decompose at 450-500°C (842-932°F) can be made into fiber or film. Stable to oxidation up to 500°C (932°F) can make flexible elastomer. Stable above 900°C (1625°F) fiber resists abrasion with low tenacity. Soluble polymer that decomposes at 385°C (725°F) prepolymer melts above 405° C (76l.°F). Service temperatures up to 288° C (550°F) amenable to fabrication. Thermoplastic use temperature —102°C (—152°F) to greater than 150° C (302°F) acid and base resistant. 

Since that time much work has been done in the area of siloxane-imide systems, especially in industrial laboratories. Therefore most of the available information is enclosed in the patent literature 168 175) and, unfortunately, description of the actual polymerization chemistry is very vague. A great majority of these applications utilized disiloxanes in high concentrations in order to obtain soluble polymers with improved toughness. 

Figures 8 and 9 show the first order kinetic plots for the isomerization and crosslinking reactions, respectively. In the data analysis the area of the isoimide peak was measured between consistent limits chosen to exclude any contribution from the 1775 cm imide band. These data were generated by measuring the area of the appropriate peak in a baseline corrected spectrum and ratioing this area to that of a reference peak (which was invarient during the experiment) in the same spectrum. This concentration indicative number was then ratioed to the concentration ratio observed on the initial scan. Plots of the log of the ratio of the concentration of the functionality at time "t" to the concentration of the functionality at t = 0 were then constructed. In order to insure that the trends in the data were not artifacts of this procedure or of the baseline correction routine, we also plotted the data in terms of peak intensity in absorbance units and observed the same trends but with more scatter in the data.

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