TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): Compound (I) is prepared by:(A) mixing 4-methylbenzaldehyde, chloroform and benzyltriethylammonium chloride at mol ratio of 1:2:2.5-1:3:4, adding dropwise 50 wt.% sodium hydroxide solution, reacting at 50-65 degrees C for 7-10 hours, diluting with deionized water, diethyl ether extracting, regulating pH at 1-2, diethyl ether extracting, removing ethyl ether, and vacuum drying to obtain 2-hydroxy-2-(4-methylphenyl)acetic acid of formula (II);(B) adding hydroquinone, methyl mandelate and sulfuric acid at mol ratio of 1:5:2-1:10:4, dissolving into acetic acid, reflow stirring for 4-10 hours, adding catalyst hydrogen peroxide, continuously reflow stirring for 1.5-5 hours, separating and purifying, and drying to obtain 3,7-di-(4-methylphenyl)benzo(1,2-b:4,5-b')difuran-2,6-dione of formula (III);(C) adding N-bromosuccinimide and benzoyl peroxide at mol ratio of 1:1:0.1-1:2:0.9, dissolving into solvent carbon tetrachloride, refluxing for 10-18 hours, and removing solvent to obtain 3,7-di-(4-bromo-methylphenyl)benzo(1,2-b:4,5-b')difuran-2,6-dione of formula (IV);(D) adding paraformaldehyde and potassium tert-butoxide at mol ratio of 1:1:0.5-1:2:1, dissolving into tetrahydrofuran, diluting by adding distilled water, extract separating, drying using anhydrous magnesium sulfate, filtering, and separating and purifying to obtain 3,7-bis(4-bis-vinylphenyl)benzo(1,2-b:4,5-b')difuran-2,6-dione of formula (V);(E) mixing 2-cyanothiophene and diisopropyl succinate at mol ratio of 1.5:1-2:1, dissolving into tert-butyl alcohol, reacting at 100-110 degrees C for 24-48 hours, cooling to 50 degrees C, adding dropwise catalyst acetic acid for 50-100 minutes, cooling, filtering, hot water and hot methanol washing, and vacuum drying to obtain 3,6-thiophene-2,5-dioxo-pyrrolo(3,4-c)pyrrole-1,4-dione of formula (VI);(F) adding anhydrous potassium carbonate and 1-bromooctane at mol ratio of 1:2:3-1:2.5:4, dissolving into N,N-dimethylformamide, heating under inert atmosphere at 145-160 degrees C for 15-20 hours, cooling to room temperature, adding water, drying, and evaporating solvent to obtain 2,5-dioctyl-3,6-thiophene-pyrrolo(3,4-c)pyrrole-1,4-dione of formula (VII);(G) adding N-bromosuccinimide at mol ratio of 2:1-0.5:1, dissolving into chloroform, stir reacting for 30-50 hours, and evaporating solvent to obtain 2,5-dioctyl-3,6-di(5-bromo-thiophene)-pyrrolo(3,4-c)-1,4-diketone of formula (VIII); and(H) adding compound (V), dissolving into dimethyl formamide, adding palladium chloride triphenylphosphine mixture at mol ratio of 1:0.05-0.5, heating to 120-140 degrees C, adding catalyst triethylamine, reflux reacting for 48-58 hours, cooling, pouring in methanol, filtering, and vacuum drying.Preferred Components: The mass ratio of sodium hydroxide solution and 4-methylbenzaldehyde is 1:1-1:2.5.