Imide concentration temperature

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). 

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... 

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

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. 

The thermal polymerization of reactive polyimide oligomers is a critical part of a number of currently important polymers. Both the system in which we are interested, PMR-15, and others like it (LARC-13, HR-600), are useful high temperature resins. They also share the feature that, while the basic structure and chemistry of their imide portions is well defined, the mode of reaction and ultimately the structures that result from their thermally activated end-groups is not clear. Since an understanding of this thermal cure would be an important step towards the improvement of both the cure process and the properties of such systems, we have approached our study of PMR-15 with a focus only on this higher temperature thermal curing process. To this end, we have used small molecule model compounds with pre-formed imide moieties and have concentrated on the chemistry of the norbornenyl end-cap (1). 

Phthalocyanine Polymers. Phthalocyanin-imide polymers show an initial decomposition temperature > 500 °C both in air and inert atmosphere (Co, Ni, Cu, Zn) as expected. An increase in the concentration of metal phthalocyanine in the copolymer increases the thermal stability [70]. Poly(Cu 2,3,9,10,16,17,23,24-octacyanophthalocyanine) represents an unique polymer showing enhanced thermal stability (1.2% wt loss at 585 °C and 1.5% wt loss at 625 °C, 21.6% at 800 °C) in He atmosphere Rapid oxidation takes place on heating above 560 °C (9% wt loss at 585 °Q [99] in air. The enhanced stability of this material is different from that of monomeric metal phthalocyanine compounds which sublime and loose most of their weight around 600 °C [99]. 

The latter property is somewhat of a mixed blessing, however. Poly(imides) are only soluble, for the most part, in extreme solvents such as concentrated sulfuric acid, fuming nitric acid and m-cresol. This lack of solubility in common solvents and their high melt temperatures render poly(imides) virtually intractable. For this reason, processing of the poly(imides) directly is often avoided by utilizing the polyfamic acid) precursor (Scheme 54). The more processable poly(amic acid) can be cast from solution, for example, and the poly(imide) may be generated in the desired configuration by thermolysis at 300 °C. 

Copolyester of p-hydroxybenzoic acid with ethylene terephthalate (PHB-PET, 60/40) was supplied by Tennessee Eastman Kodak Co., whereas polyether imide (PEI) was provided by General Electric. Co. (Ultem 1000). These polymers were dissolved together in a mixed solvent of phenol and tetrachloroethane in the ratio of 60/40 by weight at 80°C for about a week. The polymer concentration of the solution was 2 wt7.. Various PHB-PET/PEI films were cast on glass slides at ambient temperature, then dried in a vacuum oven at 60°C for two weeks. Thicker films were prepared in Petri dishes for differential scanning calorimetric (DSC) studies. 

Sodium bis-trimethylsilylamide (1 M in THF, 6.4 mL, 6.4 mmol) was added drop-wise to the imide (1.4 g, 5.7 mmol) in THF (15 mL) at -78 °C. The mixture was stirred at -78 °C for 2 h, allyl bromide (2.5 mL, 29 mmol) was then added via a syringe, and the mixture was stirred for another 3 h at -40 °C. The reaction was quenched with aqueous ammonium chloride (10 mL) at -78 °C and then warmed slowly to room temperature. The mixture was extracted with EtOAc (2 x 20 mL), and the combined organic layers were washed with 5% sodium bicarbonate, brine, dried, and concentrated. The crude product was purified via chromatography eluting with petroleum etheriether (7 1) to give 1.4 g (88%) of the olefin. 

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