The thermal degradation characteristics of a new macromonomer poly(epsilon-caprolactone) with central 4,4'-dicarbaldehyde terphenyl moieties and poly(phenylene vinylene)s with well defined (E-caprolactone), (PPV/PCL) as lateral substituents were investigated via direct pyrolysis mass spectrometry. The unexpectedly high thermal stability of the macromonomer was attributed to intermolecular acetylation of benzaldehyde yielding a hemiacetal and causing a crosslinked structure during the pyrolysis. Increased thermal stability of the PCL chains was detected for all samples. The increase in stability of PCL chains was much more pronounced than was detected for poly(p-phenylene)-graft-poly(epsilon-caprolactone) copolymer (PPP/PCL); the upward temperature shift was about 100 degrees C for PPV/PCL and only 20 degrees C for PPP/CL. This pronounced effect may be due to higher thermal stability of PPV compared to PPP and the decrease in steric hindrance for PPV with PCL side chains. (C) 2008 Elsevier Ltd. All fights reserved.