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 bedeveloped from cold crystallization or solvent induced crystallization (by exposing the glassy sample to methylene chloride).