Synthesis and characterization of oligo(oxyethylene)/carbosilane copolymers for thermoset elastomers via ADMET

Abstract

Acyclic diene metathesis (ADMET) polymerization has been used to synthesize latent reactive processable elastomers constructed of carbosilane and polyether segments. Two types of latent modes have been introduced: “chain‐internal” and “chain‐end” sites through the use of labile silicon methoxy functionalities. These latent reactive groups are inert when exposed to metathesis conditions allowing formation of the linear copolymer; subsequently exposure to moisture triggers hydrolysis of the methoxy groups and formation of a chemically crosslinked thermoset. The thermoset's mechanical response can be potentially varied from plastic to elastic behavior, depending on the ratio of carbosilane and oligooxyethylene monomers employed. Different lengths of glycols and numbers of methylene groups between them in the polymer backbone have been investigated to explore structure/property relationship. Polymers composed of oligooxyethylenes with eight methylene groups in between them exhibited fully amorphous character, while the ones with up to 20 methylene groups between glycol units showed their semicrystalline nature. The concentration of “chain‐internal” and “chain‐end” crosslink sites enhances strength; modification to the run length and structure of the soft phase enhances elasticity. Resultant materials have been subjected to mechanical tests using Instron; generated stress/strain curves have shown plastic and elastic behavior. Depending on the composition obtained samples have shown moduli from 0.3 to 115 MPa, tensile strengths from 0.6 to 10 MPa and elongations from 20 to 700%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3992–4011, 2008

Thermally crosslinked carbosiloxane and oligo(oxyethylene) polymers

“…Data were then collected as the sample was heated to 225 C, recooled to À150 C, and reheated to 225 C, all at 10 C/min. During the first heating ramp, 4b exhibited an endothermic transition at À47 C (attributed to the glass transition, similar to previously synthesized polymers 14 ), followed by a broad melting peak at 30 C (DH m ¼ 62 J/g). In addition, a broad exotherm was observed between 162 and 210 C, which undoubtedly corresponds to the exothermic ring-opening crosslinking of the silacyclobutane ring.…”

“…This led to an improvement in the mechanical properties, reflected in a modulus of 6 MPa, and a percent elongation of 400, both comparable to properties of commercial elastomers. 13,14 While the improvements were encouraging, it was clear that hydrolytically driven crosslinking has disadvantages in intrinsically hydrophobic materials. Consequently, we turned to other types of latent crosslink reactions, specifically those driven by exposure to high temperature.…”

First report of rapidly progressive glomerulonephritis in tumor necrosis factor receptor–associated periodic syndrome

“…The versatility of ADMET polymerization enables the synthesis of linear polymers with functional groups that can be used as crosslinking points 14, 16. Taking into account the good flame retardant properties obtained in our previous work with DOPO II ( M2 ) as phosphorus containing comonomer,11 we decided to use it for the preparation of flame‐retardant thermosets.…”

“…However, the low T g of these polymers can be a limiting factor for some applications. Taking into account the high functional group tolerance of the so‐called 2nd generation Grubbs metathesis catalysts,12, 13 ADMET polymerization enables the introduction of functional groups that can act as crosslinking points for the development of thermosets with improved mechanical properties 14. This work, thus, deals with the synthesis of plant oil‐based linear polyesters containing phosphorus and alcohol functionalities via ADMET.…”

Synthesis and thermal crosslinking of carbosiloxane and oligo(oxyethylene) polymers

“…Although these hydrolytic thermoset polymers exhibited interesting elastomeric behavior, their tensile strengths were not particularly high, possibly because of insufficient crosslinker concentration 19, 20. Later, Matloka et al20, 21 introduced internal and chain‐end alkoxy‐substituted silicon crosslinkers into oligo(oxyethylene)‐ and carbosiloxane‐based polymers and studied their structure/property relationships. They found that incorporation of chain‐end crosslinked materials enhanced the mechanical properties, possibly by limiting the formation of dangling chains, and that the mechanical properties of thermosets depended on the formulation.…”