title: Theoretical studies on Si-C bond cleavage in organosilane precursors during polycondensation to organosilica hybrids.
abstract: Molecular orbital theory calculations were carried out to predict the occurrence of Si-C bond cleavage in various organosilane precursors during polycondensation to organosilica hybrids under acidic and basic conditions. On the basis of proposed mechanisms for cleavage of the Si-C bonds, the proton affinity (PA) of the carbon atom at the ipso-position and the PA of the carbanion generated after Si-C cleavage were chosen as indices for Si-C bond stability under acidic and basic conditions, respectively. The indices were calculated using a density functional theory (DFT) method for model compounds of organosilane precursors (R-Si(OH)(3)) having organic groups (R) of benzene (Ph), biphenyl (Bp), terphenyl (Tph), naphthalene (Nph), N-methylcarbazole (MCz), and anthracene (Ant). The orders for the predicted stability of the Si-C bond were Ph > Nph > Bp > Ant > Tph > MCz for acidic conditions and Ph > MCz > Bp > Nph > Tph > Ant for basic conditions. These behaviors were primarily in agreement with experimental results where cleavage of the Si-C bonds occurred for Tph (both acidic and basic), MCz (acidic), and Ant (basic). The Si-C bond cleavage of organosilane precursors during polycondensation is qualitatively predicted from these indices based on our theoretical approach.
authors.affiliation: Toyota Central R&D Laboratories, Inc., Nagakute, Aichi 480-1192, Japan.
authors.forename: Soichi
authors.initials: S
authors.lastname: Shirai
authors.forename: Yasutomo
authors.initials: Y
authors.lastname: Goto
authors.forename: Norihiro
authors.initials: N
authors.lastname: Mizoshita
authors.forename: Masataka
authors.initials: M
authors.lastname: Ohashi
authors.forename: Takao
authors.initials: T
authors.lastname: Tani
authors.forename: Toyoshi
authors.initials: T
authors.lastname: Shimada
authors.forename: Shi-aki
authors.initials: SA
authors.lastname: Hyodo
authors.forename: Shinji
authors.initials: S
authors.lastname: Inagaki