Synthesis, Characterization, and Evaluation of Amine-Terminated Cycloaliphatic Substituted Polysiloxanes

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 1 H and 29 Si 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.