PREPARATION AND PROPERTIES OF HIGH-MOLECULAR-WEIGHT POLYAMIC ESTER HAVING A CYCLOBUTANE MOIETY IN THE MAIN-CHAIN

Preparation and properties of the polyimide derived from cyclobutanete tracarboxylic dianhydride (CBDA) with diamines are investigated, focus ing on the interfacial polycondensation of cyclobutanetetracarboxylic acid dimethylester dichloride (2a) with diamines. Dimethylester was co nveniently prepared from CBDA by refluxing in methanol solution. Dimet hylester consists of two regio isomers; one is alpha-type (1a) with ce ntrosymmetry, the other is beta -type (1b) with plane symmetry. Separa tion of the mixture into each of pure la and 1b was successfully perfo rmed by fractional crystallization. The structure of the first fractio n is 1a, which was determined by x-ray crystal analysis. The second fr action was necessarily assigned to 1b. 1a was converted into 2a by the reaction of thionyl chloride. The interfacial polycondensation of 2a with diamines afforded a high molecular weight polyamic ester. Polyimi de was obtained only by heating the polyamic ester to about 230-280 de grees C. The cyclobutane polyimide thus obtained was thermally stable up to 400 degrees C, and less stable under hydrolysis than polypyromel litic imide.