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A synthetic scheme was developed to prepare cationically polymerizable methyl, cyclopentyl, and cyclohexyl substituted polysiloxanes. Initially, the desired cycloalkene and dichlorosilane were reacted at high pressure (approximately 250 psi) and high temperature (120 °C) to yield the desired cycloaliphatic dichlorosilane. The chlorosilane monomers underwent an oligomerization to produce cyclic oligomers of low molecular weight (∼2000 g/mol). Polysiloxanes were produced through the acid-catalyzed ring-opening polymerization of the cyclic oligomers to yield high molecular weight polysiloxanes (∼45 000 g/mol). The polysiloxanes were then functionalized with a cycloaliphatic epoxy and alkoxysilane groups via hydrosilylation. Monomers, oligomers, and polymers were characterized by 1H and 29Si NMR, FT-IR, and electrospray ionization mass spectroscopy. The photoinduced curing kinetics and activation energies were investigated using photodifferential scanning calorimetry. Differential scanning calorimetry was used in order to observe any physical changes in the films that are brought about due to the variation of the pendant groups. The cycloaliphatic substituents raised the glass transition temperature and affected the curing kinetics when compared to a methyl substituted polysiloxane. The activation energies were found to be 144.8 ± 8.1 kJ/mol for the methyl substituted and 111.0 ± 9.2 and 125.7 ± 8.5 kJ/mol for the cyclopentyl and cyclohexyl substituted polysiloxanes.

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Cyclopentyl‐ and cyclohexyl‐substituted polysiloxanes terminated with amino groups were prepared. Initially, the cycloalkene and dichlorosilane were reacted at high pressure (approx. 250 psi) and high temperature (120 °C) to yield the cycloaliphatic dichlorosilane in a two‐step process. Both the mono‐ and disubstituted chlorosilane monomers underwent an oligomerization to produce cyclic oligomers of low molecular weight (≈2 000 g · mol−1). Amine‐terminated polysiloxanes were produced via a base‐catalyzed ring‐opening polymerization of the cyclic oligomers with 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane to yield low molecular weight polysiloxanes (≈9 000 g · mol−1, amine equivalent weight = ≈4 300 g · equiv.−1). The polysiloxanes were characterized by 1H and 29Si NMR, and Fourier transform‐infrared spectroscopy (FT‐IR). The amine‐terminated polysiloxane was mixed with a cycloaliphatic epoxy‐functionalized cycloaliphatic polysiloxane in order to produce crosslinked epoxy–amine films. The mechanical and physical properties of the film were evaluated and afford a glass transition of the material was 29.5 ± 0.7 °C for the cyclopentyl‐substituted polysiloxane and 38.6 ± 0.7 °C for the cyclohexyl‐substituted polysiloxane. Evaluation of pull‐off adhesion indicated that 0.5 MPa of normal force was required to remove the epoxy/amine film from an aluminum substrate.

Summary: An inorganic hybrid material was produced using a polysiloxane binder and metal‐oxo‐clusters which were derived from sol‐gel precursors. The continuous phase is composed of an elastomeric polysiloxane functionalized with cycloaliphatic epoxide groups. Pendant alkoxy silane groups serve as a coupling agent to form a network between the metal‐oxo‐clusters and the crosslinked polysiloxane. Methyl, cyclopentyl, and cyclohexyl substituted polysiloxanes were formulated with a variety of sol‐gel precursors (tetraethylorthosilicate oligomers, titanium(IV) iso‐propoxide, zirconium(IV) propoxide, and zinc acetate). Phase‐modulated FT‐IR, X‐ray photoelectron spectroscopy, solid state 29Si NMR, and solid state 13C NMR were used to investigate the internal structure of the mixed metal‐oxo/silicon‐oxo colloids prepared within the cured polysiloxane matrix. Results indicate that the cycloaliphatic groups inhibit the complete hydrolysis and condensation of the pendant triethoxysilane group and reaction of the sol‐gel precursors. Analysis also indicated that the metal‐oxo‐clusters were comprised of mixed species of sol‐gel precursors resulting in hetero‐bonded (SiOMetal) colloids.Possible network compositions of the cured material (a) specific metal‐oxo‐clusters, (b) hetero‐bonded metal‐oxo‐clusters, and (c) core/shell type metal‐oxo‐cluster configuration.magnified imagePossible network compositions of the cured material (a) specific metal‐oxo‐clusters, (b) hetero‐bonded metal‐oxo‐clusters, and (c) core/shell type metal‐oxo‐cluster configuration.