Amorphous Cross-linked Polyimides Type II

Generally, the aim of the study on crosslink polyimides is an attempt to enhance their gas selectivity and physical stability for gas-induced swelling and plasticization. Several 

The etherification reaction of polyimides is similar to the process of the imide ringopening reaction. It was demonstrated for the reaction of polyimides with primary diamine and epoxy agents [57,58] (for example, for 6FDA-TeMPD polyimides and tet-raglycidyldiaminodiphenylmethane (TGDDM), diethyltoluenedianune (DETDA) [57], TMPDA, 1,3-phenylenediamine (PDA) and4,4 -(9-fluorenylidene)dianiline (FDA) [58]). The density of polymers and crosslink concentration inaeased with the increase in epoxy content. 

It is known that the crossUnk reaction proceeds with participation of photo reactive benzophenone and alkyl chains under UV irradiation [59,60]. Many benzophenone-containing BTDA-based polyimides have been synthesized and their cross-linking investigated [61-69]. The same effects as discussed earlier were observed due to increases in the UV irradiation time. 

Hyperbranched polyimides can result due to the self-polycondensation reactions of AB2-, A2- and Bs-types. The preparation of hyperbranched polyimides involves chemical imidization of polyamic acid ester synthesized from AB2-monomers, which are carboxylic dianhydrides containing an ether bond and a diamine [6,19,76]. Polyamic acid in combination with a condensation agent is used because it is difficult to separate the synthesized polymer from AB2-type monomers. 

Other examples of self-polycondensation of an AB2-type monomer containing an imide-ring via etherification reactions can be found in the literature [7,10,77]. The selfpolycondensation can be performed though nucleophilic etherification of silylated phenol and aryl fluoride in diphenylsulfone at 240 °C under the presence of caesium fluoride 

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