Influence of the architecture of dendritic-like polycarbosilanes on the ceramic yield

To investigate the influence of the architecture of preceramic polymers on the ceramic yield, two dendritic-like polycarbosilanes named as K3G3 and G3 were synthesized through different routes. The obvious difference in their molecular structures is related with the distribution of allyl groups. The decomposition and rearrangement reactions of the K3G3 occurred at lower temperatures compared with that of sample G3, due to the fact that the allyl groups in G3 are located in both inner and outer molecular layers while those in K3G3 are located in the outer layers, exclusively. As a result, the residual mass of the K3G3 at 1000 °C (18 wt%) is much lower than that of the G3 sample (35 wt%). The molecular weight of the dendritic-like polymers also has an important effect on their ceramic yield which increases from 34.6 to 67.6% with the increasing molecular weight of Gn (3 ≤ n ≤ 5).