Acid-Catalyzed Rearrangement of Azidopropyl-Siloxane Monomers for the Synthesis of Azidopropyl-Polydimethylsiloxane and Their Carboxylic Acid Derivatives

Abstract

In this work, we were the first to show the possibility of synthesizing polydimethylsiloxanes (PDMSs) with azidopropyl-functional groups at the silicon atom by the classical methods for PDMS synthesis, that is, ring-opening polymerization (ROP) and catalytic rearrangement of siloxanes in the presence of a strong acid (CF3SO3H). The suggested method was used to obtain PDMSs containing azidopropyl-functional groups at both ends of the polymer chain (telechelics) as well as PDMSs with irregular structures containing different fractions (5–50%) of azidopropyl-functional groups in the main polymer chain. The suggested method also proved to be efficient for synthesizing PDMSs containing both azidopropyl- and hydridosilyl-functional groups simultaneously. As a result, PDMSs with different mutual arrangements of two types of functional groups along the PDMS chain were obtained. The method for the catalytic rearrangement of low-molecular-weight siloxanes that we used made it possible to obtain azidopropyl-functional PDMSs in a wide range of molecular weights from 2000 to 88,000 according to gel permeation chromatography (GPC) data. The possibility of further modification of the resulting azidopropyl-functional PDMS, as well as multifunctional PDMSs containing azidopropyl- and hydridosilyl-functional groups simultaneously, by azide-alkyne cycloaddition reactions was demonstrated. The polymers obtained were characterized by 1H and 29Si NMR spectroscopy and by GPC.

Ring-Opening Polymerization (ROP) and Catalytic Rearrangement as a Way to Obtain Siloxane Mono- and Telechelics, as Well as Well-Organized Branching Centers: History and Prospects

“…It is important to note that the ROP and catalytic rearrangement reactions have not only made it possible to obtain PDMS with well-known functionalities for many decades, but also open up opportunities for introducing new functions that are relevant in our time. Thus, in the work of Milenin S.A. et al, for the first time the whole variety of options for the synthesis of polydimethylsiloxanes (PDMS) with azidopropyl functional groups at the silicon atom was demonstrated by classical ring-opening polymerization (ROP) and catalytic rearrangement of siloxanes in the presence of a strong acid (CF 3 SO 3 H) (Figure 41) [160]. The proposed method was used to obtain not only PDMS containing azidopropyl functional groups at both ends of the polymer chain (telechelic), but also PDMS with an irregular structure containing various proportions (5-50%) of azidopropyl functional groups in the main polymer chain.…”

New Principles of Polymer Composite Preparation. MQ Copolymers as an Active Molecular Filler for Polydimethylsiloxane Rubbers

“…The latter feature enables MQ copolymers to act as linking agents, provided that the functional groups of raw rubber are sufficiently reactive toward the silanol functions of MQ copolymers. Amino and carboxy substituents can serve as such agents prone to interaction with silanols; owing to the ease of incorporating them into the PDMS structure, the use of these compounds is very promising [ 39 , 40 , 41 , 42 , 43 ].…”

Environment Friendly Process toward Functional Polyorganosiloxanes with Different Chemical Structures through CuAAC Reaction

“…We have previously demonstrated the possibility of obtaining α,ω-difunctional polysiloxanes with azidopropyl functional groups by the cationic ROP mechanism of octamethylcyclotetrasiloxane with bis­(3-azidopropyl)­tetramethyldisiloxane as a stopper . In this work, siloxane telechelics were obtained by the anionic ROP mechanism using bis-tetramethylammonium oligodimethylsiloxy hydroxide (TMAH) as a catalyst (Scheme ).…”

“…The click reaction of azide–alkyne cycloaddition is one of the simplest ways in terms of implementation, tolerant to the presence of various functional groups and easily passing on most substrates. Originally it was discovered as the Huisgen reaction and then improved by the Meldal and Sharpless groups to metal-catalyzed 1,3-dipolar cycloaddition chemistry; this reaction has gained enormous importance in many areas of organic chemistry, including polymer chemistry. , Recently, more and more publications have appeared on the introduction of azide and ethynyl functional groups into the structure of polyorganosiloxanes and their postpolymerization modification according to the reaction mechanism of metal-catalyzed 1,3-dipolar cycloaddition chemistry. − However, at the present stage of development of this direction, the possibilities of functionalization of such polyorganosiloxanes are insufficiently developed, which may be due to the unavailability of a wide range of initial polymers with azide or ethynyl groups.…”

“…Moreover we used a “green” strategy, a recently formulated principle for the development of chemistry based on “green” technologies, , which also affected organosilicon chemistry and at all stages of obtaining both individual and monomeric organosilicon compounds and polymers, cross-linked materials, and particles based on them . Thus, in this work, we synthesized a wide range of polydimethylsiloxane and silsesquioxane structures, including new ones, using recently developed procedures, , and a library of polymeric organosiloxanes with functional azidopropyl groups. To demonstrate the universality of our proposed approach, we first proposed the anionic ring-opening polymerization (AROP) method for the preparation of azido-functional telechelics PDMS.…”