Synthesis of New Polyfunctional Cage Oligosilsesquioxanes and Cyclic Siloxanes by Thiol-ene Addition

Abstract

A novel octakis-2{ [3-(trimethoxysilyl)propyl] thio}ethyl-octasilsesqioxane (POSS-M24) was synthesized by radical thiol-ene addition of 3-mercaptopropyltrimethoxysilane, (MPTMS) to octavinyloctasilsesquioxane, (POSS-V8) in the presence of 2,2 0 azobisisobutyronitryl under mild conditions (60°C, toluene solution). Nano-building POSS units bearing both types of groups, 2-[3-(trimethoxysilyl)propylthio]-ethyl and vinyl, pendant to the POSS-cage were obtained by partial addition of MPTMS to the vinyl functions. Finally the thiol-ene addition of MPTMS to 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (V 3 ) and 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (V 4 ) were explored. The structures of the thiol-ene addition products were confirmed by 29 Si NMR and mass Spectroscopy.

Star-Shaped and Linear POSS-Polylactide Hybrid Copolymers

“…The general features of the mechanism of this free radical process were described earlier [26,36,37,38,39]. In all cases studied the addition occurs with high yield and high selectivity according to the anti-Markovnikov rule.…”

“…We studied the thiol-ene addition of 6-mercapto-1-hexanol (MCH) to vinyl groups bound to silicon atoms of the silsesquioxane cage, initiated by 2,2′-azobisisobutyronitrile (AIBN). The general features of the mechanism of this free radical process were described earlier [ 26 , 36 , 37 , 38 , 39 ]. In all cases studied the addition occurs with high yield and high selectivity according to the anti-Markovnikov rule.…”

“…This thiol-ene addition [27] serves as a convenient synthetic tool, particularly in the area of POSS materials [17,24,25,26,27,28,29,30,31]. This regioselective process, proceeds under mild conditions and tolerates many solvents, and functional groups.…”

“…Previously we proved that (3-mercaptopropyl)trimethoxysilane can react with vinyl groups at the silicon atoms of octavinyloctasilsesquixane to afford POSS having a variable number of alkoxysilyl functions [ 26 ]. This thiol-ene addition [ 27 ] serves as a convenient synthetic tool, particularly in the area of POSS materials [ 17 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. This regioselective process, proceeds under mild conditions and tolerates many solvents, and functional groups.…”

Evaluation of thiol‐ene click chemistry in functionalized polysiloxanes

“…Multiple investigators have confirmed that the thiol‐ene reaction retains its “click” features in the presence of silicones; yet their work has generally been limited to the application of the thiol‐ene reaction rather than the characterization of its mechanism. Wijas and Chojnowski, for example, have verified that the thiol‐ene addition proceeds under mild conditions and reaches quantitative yields in the functionalization of silsesquioxanes 17. Moreover, Kim et al have documented rapid, homogenous network formation under ambient conditions without solvent or notable oxygen inhibition in the production of dielectric materials via photopolymerization of thiol‐ene functionalized oligosiloxanes 18.…”