Functionalization Methodology for Synthesis of Silane-End-Functionalized Linear and Star Poly(aryl isocyanide)s by Combination of Cationic Polymerization and Hydrosilylation Reaction

Abstract

The combination of metal-free borates or borane mediated nonliving cationic polymerization of aryl isocyanides and hydrosilylation reaction of hydrosilanes affords a general and effective functionalization methodology to synthesize silane-end-functionalized linear and star poly(aryl isocyanide)s. The configurations, end group types, and molecular weights of these silane-end-functionalized poly(aryl isocyanide)s can be easily tuned by varying the type and concentration of hydrosilanes. A variety of monofunctional hydrosilanes such as PhMe2SiH, (4-iPrC6H4)Me2SiH, Ph3SiH, Et3SiH, iPr3SiH, and (OEt)3SiH have been successfully applied to the synthesis of linear poly(aryl isocyanide)s with different silane-end-functional groups having a one-handed helical conformation or an aggregation-induced emission (AIE) characteristic (activity up to 1.5 × 107 g/(mol of cat.·h), Mn up to 8.4 × 105), while two multifunctional hydrosilanes PhSiH3 and 1,3,5-(Me2SiH)3C6H3 are conductive to prepare star poly(aryl isocyanide)s and copoly(aryl isocyanide)s having one central core of multifunctional silane with a one-handed helical conformation and/or an AIE characteristic (activity up to 3.4 × 106 g/(mol of cat.·h), Mn up to 9.1 × 104). 1H, 29Si, and 1H-29Si HMBC NMR, Fourier transform infrared spectroscopy (FT-IR), electrospray-ionization mass spectrometry (ESI-MS), and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) analysis confirm the presence of silane-end-functional groups in these linear and star poly(aryl isocyanide)s. The mechanism study based on density functional theory (DFT) calculations suggests that hydrosilane plays a dual functional role of the chain transfer agent and regenerated cationic initiator in the [Ph3C][B(C6F5)4]-initiated cationic polymerization of aryl isocyanides.