TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No preparation method is given. Preferred Components: The polyamic acid is obtainable by a ring-opening and addition polymerization reaction of diamines, including a first diamine and a second diamine, and a tetracarboxylic dianhydride, where the first diamine is the diamine compound (I), the second diamine is diamine compounds of formula (II)-(V) and the tetracarboxylic dianhydride includes a tetracarboxylic dianhydride compounds of formula (VI), hexahydro-furo(3',4':3,4)cyclopenta(1,2-c)pyran-1,3,5,7-tetraone, 5-(2,5-dioxo-tetrahydro-furan-3-yl)-7-methyl-3a,4,5,7a-tetrahydro-isobenzofuran-1,3-dione, 5-(2,5-dioxo-tetrahydro-furan-3-yl)-3a,4,5,9b-tetrahydro-naphtho(1,2-c)furan-1,3-dione or tetrahydro-(3,3')bifuranyl-2,5,2',5'-tetraone. The molar ratio of the first diamine to a total amount of the diamines is 20-99%. The number average molecular weight of polyamic acid is 3x 103-5x 105.s = 5-13; andR1-R4 = H, F, or 1-4C alkyl. SPECIFIC COMPOUNDS - 2 Compounds (I) are disclosed e.g. (4-amino-phenoxy)-acetic acid 2-(4-amino-phenyl)-ethyl ester of formula (Ia) and (4-amino-phenoxy)-acetic acid 2-(2-(4-amino-phenoxy)-acetoxy)-ethyl ester.    EXAMPLE - After 4-nitrophenoxyacetic acid (0.8 g), 2-(4-nitrophenyl)ethanol (2.04 g), and 4-dimethylaminopyridine (0.40 g) were mixed, tetrahydrofuran (6.5 ml) was added. Then, after cooling to 0 degrees C was conducted and dicyclohexylcarbodiimide (0.92 g) was added, agitation was conducted at 50 degrees C for 24 hours. Furthermore, after a produced dicyclohexylurea was filtered out by means of filtration under a reduced pressure, tetrahydrofuran was distilled out by using an evaporator. After an obtained solid component was dissolved in dichloromethane so that its content was 5% by mass, dichloromethane was distilled out by using an evaporator to obtain (4-nitro-phenoxy)-acetic acid 2-(4-nitro-phenyl)-ethyl ester. After (4-nitro-phenoxy)-acetic acid 2-(4-nitro-phenyl)-ethyl ester, ethanol (20 ml), and tetrahydrofuran (3 ml) were mixed, palladium-carbon (0.104 g) was added. Then, after filtration was conducted by using a double filter paper to remove palladium-carbon, tetrahydrofuran and ethanol were distilled out by using an evaporator. Furthermore, after filtration was conducted under a reduced pressure, vacuum drying was conducted at room temperature to obtain (4-amino-phenoxy)-acetic acid 2-(4-amino-phenyl)-ethyl ester.