Poly(cyclosilane) Postpolymerization Hydrosilylation

Postpolymerization functionalization is a key strategy
in the diversification
of polymeric materials for the conferral of tailored properties. Poly(cyclosilane)s
are structurally complex polymers with an all-silicon backbone, featuring
a periodic array of hydrido (Si–H) side chains that are potentially
suitable for postpolymerization functionalization via hydrosilylation.
At the same time, classical methods for hydrosilylation employing
Pt- or Pd-based catalysts can result in Si–Si bond scission.
Herein, we demonstrate borane-catalyzed hydrosilylation reactions
between α-olefins and small molecules or three distinct poly(cyclosilane)
architectures. We investigate chemoselectivity for end group versus
internal Si–H groups and find that 29Si cross-polarization
magic angle spinning can provide insight on site-selectivity in the
functionalization of a complex poly(cyclosilane). We further show
that postpolymerization hydrosilylation, converting oxidatively sensitive
Si–H groups to Si–alkyl chains, modulates solubility
and physical characteristics, optical properties, pyrolytic reactivity,
and air sensitivity.