Hybrid silalkylene polysiloxanes: Synthesis and thermal properties

The three-step synthesis of polysilalkylene siloxanes or hybrid silicones HO-[Si(CH3)(R)C2H4R'C2H4Si(R)(CH3)O](n)-H is presented. First, the hydrosilylation of alpha,omega-dienes H2C=CH-R'-CH=CH2 (where R' = C6H12 and C2H4) with various chlorosilanes HSi(CH3)(R)Cl (where R = CH3, C8H17, C6H5) is reported. Then, the obtained bis-chlorosilanes are quantitatively hydrolyzed into the corresponding bis-silanols. Finally, the bis-silanols are polycondensed in the presence of tetramethylguanidine/trifluoroacetic acid to give the hybrid silicones. All the products were characterized by H-1 and Si-29 NMR spectroscopies and the silicones were analyzed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The influence of R and R' groups on the thermal properties of the silicones is studied. These properties are compared to those of a polydimethylsiloxane (PDMS), a polyphenylmethyl-p-siloxane (PPMS) and a poly(para-silphenylene siloxane) HO-[Si(CH3)(2)-p-C6H4-Si(CH3)(2)O](n)-H prepared from commercial PDMS and PPMS oligomers and from 1,4-bis(hydroxydimethyl)benzene. (C) 1997 Elsevier Science Ltd.