Thermal polydimethylsiloxane degradation. Part 2. The degradation mechanisms

The products of the thermal degradation of polydimethylsiloxane (PDMS) are determined by the heating conditions, since two competing mechanisms are involved. Cyclic oligomers are formed in the low degradation temperature range and during slow heating in programmed degradation. This involves molecular splitting of oligomers from loop conformations of the PDMS chain favoured by its flexibility, and assistance on the part of empty silicon d-orbitals. Methane and oligomers are formed in the high temperature range and during fast heating. This shows that homolytic scission of Si-CH(3) also takes place and is followed by hydrogen abstraction. (C) 2002 Elsevier Science Ltd. All rights reserved.