Thermal degradation of model linear and star-shaped polyisoprene molecules

The thermal degradation behavior, in the absence of air, of model star-shaped and linear polyisoprenes with silyl alkyl groups, prepared using anionic polymerization techniques and chlorosilanes as linking agents, has been investigated and compared with that of model linear polyisoprenes. Thermal stabilities were examined by thermogravimetry and differential scanning calorimetry, while analysis of degradation products and of polymer residues obtained after different thermal treatments was performed by gas chromatography-mass spectrometry, ¹H-NMR, FTIR and size exclusion chromatography. The temperature at which polymer decomposition takes place, the shape of the weight loss curves and the nature of the compounds formed during the degradation seems not to be influenced by the structural differences or the presence of silyl alkyl groups in the polyisoprene molecules. However, the star-shaped polymers show a higher tendency for coupling and cross-linking during degradation.