Controlled Synthesis of Siloxane Copolymers Having an Organosulfur Group by Polymerization of Cyclotrisiloxanes with Mixed Units

Abstract

The preparation of poly(dimethylsiloxane)s having part of the siloxane units substituted with a model organic thioether was investigated. The sulfur group was generated by the ene−thiol addition to the vinyl function bound to silicon. Two synthetic routes to this copolymer were compared (i) one-step kinetically controlled polymerization of organosulfur-substituted hexamethylcyclotrisiloxane and (ii) two-step synthesis including kinetically controlled polymerization of 1,3,3,5,5-pentamethyl-1-vinylcyclotrisiloxane followed by the thiol addition to the vinyl group in the polymer. A cryptand−lithium silanolate complex generated from [(trimethylsilyl)methyl]lithium was selected as the initiator in this polymerization, while tert-butyl mercaptan was used as the hydrosulfidation reagent. It was shown that synthesis routes lead to a high yield of copolymers having a fairly regular chain structure. The arrangement of siloxane units in the polymer chain was controlled by the propagation step. Polymerization of the vinyl-substituted monomer exhibited a significant degree of regioselectivity as one of the three possible modes of the monomer ring opening contributed over 70% to the propagation. Addition of t-BuSH to the vinyl group in the polymer proceeded without rearrangement of the polymer chain and could be performed without any side reaction of the vinyl group. Model copolymers of regular alternating structure were synthesized by the heterofunctional polycondensation of [2-(tert-butylthio)ethyl]methyldichlorosilane with a series of diols, HO(Me2SiO) n H, n = 1−4. They were used for comparison with the copolymers obtained by ring-opening polymerization.

Formation and Properties of Responsive Siloxane‐Based Polymeric Surfaces with Tunable Surface Reconstruction Kinetics

“…Implementing the thiol-ene addition reaction on PVMS networks, a route others demonstrated with fluid polymers, [15,[22][23][24] we modified PVMS substrates with 11-dodecanethiol (HS(CH 2 ) 11 CH 3 ) and 3-mercaptopropionic acid (HS(CH 2 ) 2 COOH). The addition to the vinyl bond was confirmed via the elimination of the C --C peaks at 960, 1407, and 1587 cm À1 in Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR).…”

Base catalyzed proton transfer polymerization of 1-hydroxypentamethylcyclotrisiloxane. Comparison of hyperbranched polymer microstructure and properties to those of highly regular linear analogs

“…Monosubstituted pentamethylcyclotrisiloxanes undergo AROP with a high degree of chemoselectivity and regioselectivity. [28,29] Highly regular linear polysiloxanes were prepared by AROP or by acid catalyzed ring opening polymerization (ACROP) of 1-(phenyldimethylsiloxy)pentamethylcyclotrisiloxane (3). Isomeric hyperbranched polysiloxane (2), was obtained via a phosphazene P 4 -t-Bu superbase catalyzed proton transfer polymerization (BCPTP) of 1-hydroxypentamethylcyclotrisiloxane (1) followed by quenching with phenyldimethylchlorosilane.…”

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

“…Thiol-ene addition has been successively used for the synthesis of functionalized carbosilane dendrimers [26,27]. This reaction was also proved to be useful for the functionalization of POSSes [6,[28][29][30][31] and polysiloxanes [32][33][34][35][36]. Two different strategies were used for this purpose.…”

“…The reverse method, i.e. the addition of a thiol to alkene-POSS or polysiloxane, which is used in this research, was also practiced [6,28,29,[31][32][33][34][35].…”