METHODS FOR SYNTHESIS OF POLYETHERIMIDES

The review summarizes and systematizes the currently known data on the synthesis of polyetherimides. Polyetherimides are a promising class of high-quality polymeric materials with a valua-ble set of properties that can be directed to the appropriate design of the polymer chain. Thus, to obtain polyetherimide with a lower glass transition temperature, as much as possible of ether bonds are introduced into the macromolecule, as well as m-phenylene fragments that increase the flexibility of the polymer chain. Polyetherimides of this structure are amorphous and soluble in a number of amide solvents and chlorinated hydrocarbons. Three main methods for the preparation of polyetherimide are discussed in detail: high-temperature polycondensation by nucleophilic substitution in solution, polycondensation in a melt, and production of polyetherimide directly during extrusion. The most promising method for today is the method of high-temperature polycondensation in solution by the reaction of nucleophilic aromatic substitution. As a halogen-containing monomer, chlorine or fluorophthalic anhydrides are used in the synthesis. The reaction of diamines with chlorophthalic anhydride proceeds at lower rates in comparison with the fluorine-containing analog. However, the use of fluorophthalic anhydride proved to be inexpedient from the economic point of view. The economic availability of the corresponding nitrosubstituted phthalic derivatives and high rates of displacement of nitro groups with the help of aryl oxide ions allow to product the commercially avail-able polymers. As solvents, aprotic dipolar (dimethylsulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, etc.), nonpolar organic (o-dichlorobenzene, methylene chloride, etc.) and phenolic solvents can be used. However, the increasing attention of researchers is attracted to the synthesis in the environment of o-dichlorobenzene.