Abstract

Novel co-condensing agents of the type R′Si(OMe)₂(CH₂)₃R₂Si(CH₂)₃Si(OMe)₂R′ {3[Me₂Si(C₃D⁰)₂] (3a), R = Me, R′ = Me; 3[Me₂Si(C₃T⁰)₂] (3b), R = Me, R′ = OMe; 4[Et₂Si(C₃D⁰)₂] (4a), R = Et, R′ = Me; 4[Et₂Si(C₃T⁰)₂] (4b), R = Et, R′ = OMe} were synthesised by hydrosilylation of the corresponding diallyldialkylsilanes 1, 2 with dichloro(methyl)silane and trichlorosilane, respectively, followed by treatment with trimethyl orthoformate. These precursors were sol–gel processed with or without PhSi(OMe)₃ [Ph(T⁰)] to give the xerogels X3a–d, X4a–d. The polysiloxane matrices, the degree of condensation and the integrity of the hydrocarbon backbone were investigated by means of solid state NMR spectroscopy (¹³C, ²⁹Si). To study the polymer dynamics in the dry state ²⁹Si CP/MAS NMR measurements of relaxation times (T_1ρH) and cross-polarisation parameters (T_SiH) were carried out. ¹H HR/MAS NMR experiments and T_1ρH measurements in different solvents were undertaken to get information on the mobility of the polymers in suspension. Scanning electron microscopy (SEM) images show the morphology of the polymers and energy dispersive X-ray spectroscopy (EDX) suggests that the distribution of the elements agrees with the applied stoichiometry.