Silacyclobutane-Functionalized Siloxane Thermosets:  An Examination of Their Properties and Potential as Copper Metal Site Selective Coatings

Abstract

A diphenylsiloxane oligomer with cross-linkable silacyclobutane functionalities at the terminal positions was prepared by the reaction of hexaphenyltrisiloxane diol with 1-chloro-1-methyl-1-silacyclobutane. When coated on inert surfaces, such as glass and plastics, the oligomer cured in air to a hard coating at temperatures above 220 °C, or above 110 °C in the presence of dissolved catalytic species such as platinum or copper complexes. The cured film provided a hard clear coating with a relatively high modulus (810 MPa) and good thermal stability. When coated onto the surface of metallic copper, the oligomer cured rapidly in air when heated to a temperature of 130 °C, without added catalyst. The catalytic species responsible for initiating the ring-opening polymerization of the silacyclobutane groups at the lower temperature are derived from the copper metal surface. Copper plates coated with a photopatterned spin-on-glass film were used to demonstrate the selectivity of the cure process for exposed metallic copper surfaces. This technology offers the potential to specifically apply electrically insulating silacyclobutane functional materials to the surface of copper conductors while deposition on other nonmetallic components is avoided.