Poly(ether ketone ether ketone ketone) containing meta|phenylene linkage (PEKEKK(T/I)) was synthesized by electrophilic Friedel|Crafts acylation condensation of 1,4|diphenoxybenzophenone with terephthaloyl chloride (T) and isophthaloyl chloride (I) with a T/I ratio of 1 and characterized by IR、DSC、TGA and WAXD. PEKEKK(T/I) has two different crystal structures: a conventional Form I structure, the same as that observed in PEEK and PEK, wich is usually developed from melt crystallization, and a new Form Ⅱ structure which can be developed from cold crystallization or solvent induced crystallization (by exposing the glassy sample to methylene chloride). Synthesis of diphenoxybenzophenone with terephthaloyl chloride (T) and isophthalyl (TKE) (PEKEKK (T / I)) was synthesized by electrophilic Friedel | PEKEKK (T / I) has two different crystal structures: a conventional Form I structure, the same as that that observed in PEEK and PEK (I) with a T / I ratio of 1 and characterized by IR, DSC, TGA and WAXD. , wich is usually developed from melt crystallization, and a new Form II structure which can be developed from cold crystallization or solvent induced crystallization (by exposing the glassy sample to methylene chloride).