Metathesis degradation of poly(butadiene‐alt‐propene)

Abstract

AbstractPoly(butadiene‐alt‐propene) (1) was degraded by metathesis reaction using symmetric olefins (3‐hexene and 4‐octene) in chlorobenzene solution in the presence of WCl6/(CH3)4Sn as catalyst. Identification of the degradation products by means of a combination of gas chromatography (GC) and mass spectrometry (MS) revealed small amounts of “defects” in the almost ideally alternating copolymer 1. These were non‐alternating sequences of 2‐butenylene and methylethylene units, vinylethylene units and branching points. In addition, the metathesis degradation of 1 with 4‐octene was investigated kinetically between 15 and 40°C. The measurements confirm that the thermodynamically stable 4‐methylcyclohexene is the final product. This can be formed directly from the polymer and via oligomeric products. The formation of these intermediates is preceded by an induction period. Their concentrations pass maxima, the positions of which depend on the size of the molecules and on the temperature.