The triad monomer unit sequence distribution and the cis and hans Linkage configurations at the cyclic citraconic anhydride units are quantitatively determined for the copolymers of citraconic anhydride (alpha-methylmaleic anhydride) (CA) and styrene (ST) prepared with AIBN in CCl4 solutions at 50 degrees C. Semi-alternating copolymers are obtained for most feed compositions with rigidly alternating copolymers being formed when CA in feed is more than 90%. Greater than 50% of the linkages at CA units are found to be in cis configuration in semi-alternating copolymers. This may be explained if the donor-acceptor complex formed between CA and ST participates in the copolymerization.