A new difluoride 4,5-bis(4-fluorobenzoyl)-1-methylcyclohexene (DFKK) has been prepared with fumaryl chloride, fluorobenzene, and 2-methyl-1,3-butadiene as starting materials through two steps of reactions. This DFKK monomer undergoes reaction with 2,2-(p-hydroxyphenyl)-iso-propane (BPA) in the presence of excess anhydrous potassium carbonate in sulfolane to give a high molecular weight reactive poly(ether ketone ketone) (PEKK) that is very soluble in solvents such as chloroform and N,N-dimethylformamide at room temperature, has glass transition temperature of 182degreesC, and is easily cast into flexible and bale ivory film with tensile strength of 64 MPa. The 5% weight loss temperature is 407degreesC. Ring-closing reaction of PEKK with hydrazine gives cyclized PEKK (CPEKK) with improved thermal stability and reduced solubility.