Polar aprotic solvents poly 2-

Synthesis and Properties. Several methods have been suggested to synthesize polyimides. The predominant one involves a two-step condensation reaction between aromatic diamines and aromatic dianhydrides in polar aprotic solvents (2,3). In the first step, a soluble, linear poly(amic acid) results, which in the second step undergoes cyclodehydration, leading to an insoluble and infusible PL Overall yields are generally only 70—80%. 

Terminally unsaturated fluonnated alkenoic acids can be obtained from poly-fluorocycloalkenes by reaction with potassium hydroxide m rert-butyl alcohol [24] (equation 26) The use of a tertiary alcohol is critical because primary and secondar y alcohols lead to ethers of the cycloalkenes The use of a polar aprotic solvent such as diglyme generates enols of diketones [26] (equation 27) The compound where... 

Poly(ether ketone)s 3, 4, 5, 6, and 7 were soluble in polar aprotic solvents such as DMAc and NMP and in chlorinated solvents such as chloroform. The improved solubility of these fluorinated poly(ether ketone)s can be explained by the presence of both the flexible hexafluoroisopropylidene groups and the bulky 1,4-naphthalene moieties, which inhibit polymer crystallization and facilitate the penetration of solvent molecules between the polymer chains. 

Reaction of 1 with 4-fluorobenzoyl chloride yielded the difluoro-containing monomer 2, which is readily polymerized with a bisphenol using potassium carbonate in /V, /V-dimethy 1 acetamide to yield poly(ether ketone)s. The five poly-(ether ketone)s prepared were soluble in polar aprotic solvents and were cast into flexible, creasable films showing good thermal stability. We have demonstrated that 1 -phenoxy-substituted naphthalene moieties undergo a Friedel-Crafts acyla-... 

The per(poly)fluoroalkylation of olefins by per(poly)fluoroalkyl chlorides, initiated by ammonium peroxydisulfate and sodium formate, is also reported. The reaction proceeds smoothly in polar aprotic solvents. The presence of functional groups like sodium car-boxylate or sulfonate in the polyfluoroalkyl chloride appears to facilitate the reaction. This reaction represents the first example of the reactivity of per(poly)fluoroalkyl chlorides. 

The classical synthetic pathway to prepare polyimides consists of a two-step scheme in which the first step involves polymerization of a soluble and thus processable poly(amic acid) intermediate, followed by a second dehydration step of this prepolymer to yield the final polyimide. This preparative pathway is representative of most of the early aromatic polyimide work and remains the most practical and widely utilized method of polyimide preparation to date. As illustrated in Scheme 4, this approach is based on the reaction of a suitable diamine with a dianhydride in a polar, aprotic solvent such as dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), dimethylformamide (DMF), or AT-methylpyrrolidone (NMP), generally at ambient temperature, to yield a poly(amic acid). The poly(amic acid) is then cyclized either thermally or chemically in a subsequent step to produce the desired polyimide. This second step will be discussed in more detail in the imidization characteristics section. More specifically, step 1 in the classical two-step synthesis of polyimides... 

In a two-phase system similar to that used by Price, Stamatoff (29) obtained from 2,6-dichloro-4-bromophenol a branched polymer having approximately the statistical ratio of ortho and para ether linkages. When the reaction was carried out using the anhydrous salt of the phenol in the presence of highly polar aprotic solvents, such as dimethyl sulfoxide, the product was the linear poly(2,6-dichlorophenylene oxide) (Reaction 23). 

PEG-PS supports were developed to allow better solvation of the growing peptide chain in polar aprotic solvents commonly used for peptide synthesis. The PEG resins were also shown to have excellent mechanical stability, which allows their use in continuous-flow systems [19]. Other PEG-con-taining supports include poly(trimethylolpropane ethoxy late [14/3 EO/ OH)triacrylate-co-allylamine] (CLEAR) [28] and poly(A,A-dimethylac-rylamide-co-bisacrylamido polyethylene glycol-co-monoacrylamidopoly-ethylene glycol) (PEGA) [29,30], and have demonstrated promising properties. 

Some current preparations of poly(arylene ether)s are carried out by nucleophilic displacements of activated aromatic dihalides or dinitro groups by alkali metal bisphenates. The reactions take place in polar aprotic solvents. The glass transition temperatures, tensile strengths, and tensile moduli of these materials tend to increase when heterocyclic units are incorporated into the backbones. Poly(arylene ether)s containing imide, phenylquinoxaline, imidazoles, pyrazoles, l,3,4-oxadiazoles, benzoxazoles, and benzimidazoles groups were prepared. 

Lee et al. [169] reported the preparation of new soluble and intrinsically photosensitive poly(amide-co-imide)s containing p-phenylenediacryloyl moiety. The copolymers were formed from p-phenylenediacryloyl chloride, aromatic dianhydrides, and two equivalents of aromatic diamines. The products were subsequently imidized by reactions with the poly(amide-co-amic acid), acetic anhydride, and pyridine. The polymers were stable up to 350°C, showed good solubility in polar aprotic solvents, and became insoluble after the irradiation due to the photodimerization of phenylenediacryloyl moiety. The photo-reactivity increases with the irradiation temperature [169]. 

Phosphorus-containing polymers have shown excellent thermal stability and good adhesion characteristics. In addition, phosphorus-containing polymers have been found to show excellent flame retardance [66,67]. All of the synthesized poly(arylene ether phosphine oxide)s (PAEPOs) (2-45 to 2-48) (Table 2.7) [68] exhibited excellent solubility at room temperature, including polar aprotic solvents, and also in chloroform, CH2CI2, and THF. These polymers also had good solubility... 

Mercer et al. [62] synthesized a fluorinated poly(arylene ether ketone) with sulfone moiety containing 1,4 naphthalene units (Scheme 2.23) and studied their properties. The polymer was soluble in polar aprotic solvents and in chloroform with an Mw 34,300g/mol. The Tg of the polymer was high as 205 °C and onset thermal degradation temperature was 502 °C in an air atmosphere. 

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