Alternating structures in copolymers as elucidated by microozonolysis

Abstract

The technique of microozonolysis followed by gas chromatography has been used to determine the amount of 1,2‐structures occurring as 1,4–1,2–1,4 sequences in n‐butyl‐lithium‐initiated polybutadienes. The product obtained from the ozonolysis of these sequences, 3‐formly‐1,6‐hexanedial, was directly proportional to the 1,2 (vinyl) content of the polymers as measured by infrared or NMR spectroscopy. An unusual ozonolysis product, 4‐octene‐1,8‐dial, has been found in the ozonolysis products of high‐1,4 poly‐butadienes. Ozonolysis has also been used to determine alternating structures in propylene‐butadiene copolymers. The product obtained from ozonolysis of such structures is 3‐methyl‐1,6‐hexanedial. Ozonolysis of a polyisoprene containing equal amounts of 1,4 and 3,4 structures indicated it to have a nonalternating structure with long blocks of 1,4‐isoprene units. Gas chromatographic separation was accomplished by using sucrose acetate isobutyrate with Carbowax 20M as the liquid phase. Retention times were established by using model compounds where possible.