Cyclolinear polycarbosilanes – a recent addition to the class of organosilicon polymers

Abstract

This article focuses on a relatively new group of organosilicon polymers known as cyclolinear polycarbosilanes (CLPCS). This group of polymers contains 1,3-disilacyclobutane (DSCB) rings, i.e., cyclo-{RSi(CH(2))(2)SiR}-, bridged by various linking groups, so as to form linear chains with regularly spaced, strained, rings that function as latent sites for cross-linking. This ring-chain, or "beads-on-a-string", type polymer has the general formula, [-{RSi(CH(2))(2)SiR}-Y-](n), where R and Y can be a variety of different groups, such as: R = -CH(3), -C(6)H(5) and -C(6)H(4)(CH(3)); Y = -(CH(2))(x)-, -C(6)H(4)-(CH[double bond, length as m-dash]CH)-C(6)H(4)-, and -C(6)H(4)-. Depending, in part, on the linking group, these CLPCS have been obtained by using two different synthesis methods, acyclic diene metathesis polymerization (ADMET) and Grignard coupling reactions. The resultant polymers exhibit a wide variation in physical properties, which depend on the nature of the silicon substituents, R, and the bridging group, Y. However, they also share some important characteristics, such as a relatively low glass transition temperature, amenability to the formation of thin films and coatings via spin-coating, and the tendency to undergo cross-linking on heating to 200-300 °C. The synthesis, characterization, and properties of these CLPCS are reviewed and their potential for application in such widely divergent areas as microelectronics processing (as low-k materials), protective, insulating coatings for Cu and other substrates, and photoluminescent films are described.

Grignard condensation routes to 1,3‐disilacyclobutane‐containing cyclolinear polycarbosilanes

“…The RO enthalpy for this polymer, obtained from the integrated area under the exothermic peak, is directly proportional to the molar content of the DSCB ring. The molar RO enthalpy of the DSCB ring in the polymer was approximately −40 kJ/mol, which was consistent with the data previously reported for alkyl‐ or aryl‐substituted DSCB containing compounds and polymers …”

“…1,3‐Disilacyclobutanes (DSCBs) are known to undergo thermally, or catalytically, induced ring opening polymerization (ROP) to produce linear polymers containing alternating silicon and carbon atoms in the backbone, due to the substantial strain energy of the four‐membered (Si‐C) 2 ring . We previously reported the use of DSCB rings embedded in a cyclolinear polycarbosilane (CLPCS) as a thermosetting polymer . A series of CLPCSs with DSCB rings alternating with bridging alkylene groups were prepared via acyclic diene metathesis (ADMET) polymerization of diolefin‐terminated DSCB monomers, followed by in‐situ reduction of the internal double bonds.…”

Polymer‐Derived SiC/B4C/C Nanocomposites: Structural Evolution and Crystallization Behavior

“…2 Various polymeric and oligomeric carbosilanes having Si atoms linked by methylene (CH 2 ) groups were studied as SiC precursors. [3][4][5] SiC ceramics with different shapes and properties can be obtained by changing precursors and processing methods. 6,7 The synthesis of linear silylene-acetylene and disilylene-acetylene polymers with high molecular weight and high yield as SiC/C polymeric precursors was finished by using trichloroethylene instead of acetylene.…”

“…Polymers with good processing and shaping ability are increasingly applied as ceramic precursors as silicon‐based polymer‐derived ceramics (PDCs) were synthesized directly by the pyrolysis of organosilicon polymers in 1960s . Various polymeric and oligomeric carbosilanes having Si atoms linked by methylene (CH 2 ) groups were studied as SiC precursors . SiC ceramics with different shapes and properties can be obtained by changing precursors and processing methods .…”

A novel one-pot synthesized organosiloxane: synthesis and conversion to directly thermo-crosslinked polysiloxanes with low dielectric constants and excellent thermostability

“…Therefore, directly thermo-crosslinkable organic siloxanes are required. [11][12][13][14][15] Such characteristics of the BCB group inspire us to develop new directly thermo-crosslinkable polysiloxanes. 1,5,9,10 Previously, we reported the synthesis and properties of a new polysiloxane containing trifluorovinylether (-OCFvCF 2 ) groups which was directly thermo-crosslinkable and the crosslinked networks showed high heat resistance and good dielectric properties.…”