α-Trialkoxysilyl Functionalized Polycyclooctenes Synthesized by Chain-Transfer Ring-Opening Metathesis Polymerization

Abstract

International audienceRing-opening metathesis polymn./cross-metathesis (ROMP/CM) of cyclooctene (COE) or 3-alkyl-substituted COEs (3R-COEs, R = Et, n-hexyl) using several trialkoxysilyl monofunctionalized alkenes as chain-transfer agents (CTAs; vinyl trimethoxysilane (1), allyl trimethoxysilane (2), and 3-(trimethoxysilyl)propyl acrylate (3)) and various Ru-carbene-alkylidene catalysts afforded several trialkoxysilyl mono- and difunctionalized polyolefins. The formation of α-monofunctional (MF), α,ω-difunctional (DF), isomerized α-monofunctional (IMF), linear nonfunctional (LNF), isomerized linear nonfunctional (ILNF), and cyclic nonfunctional (CNF) PCOEs is rationalized by a two-stage mechanism. First, formation of monofunctionalized (MF) and nonfunctionalized (LNF, CNF) macromols. takes place through a ROMP/CM along with RCM (ring-closing metathesis) process. Subsequently, C=C isomerization (ISOM) combined with a second CM process give isomerized (ILNF, IMF) and difunctionalized (DF) macromols. The nonfunctionalized polymers (CNF, LNF, and ILNF) were formed in minor quantities compared to the trialkoxysilyl-functionalized polymers (MF, IMF, and DF), as evidenced by NMR and MALDI-ToF MS analyses and fractionation expts. The rate and selectivity of the reaction varied with the nature of the CTA, COE substituent, catalyst, and to a lesser extent of the solvent. The use of 1,4-benzoquinone (BZQ) as additive allowed inhibiting completely the ISOM process. Alternatively, steric hindrance in 3-RCOEs substituted monomers resulted in an ISOM-free process with selective formation of MF polymers. The reactive Grubbs' second-generation catalyst (G2) afforded the best compromise in terms of productivity, reactivity, and selectivity. Under optimized conditions favoring the formation of MF/DF, i.e., in CH2Cl2 at 40 °C for 24 h with [COE]0/[CTA 3]0/[G2]0/[BZQ]0 = 2000:20-200:1:100, the polymn. was rather well-controlled. While CTAs 1 and 3 selectively gave mixts. of MF and DF, allyl CTA 2 resulted in a mixt. of IMF, MF, and DF

Simple access to alkoxysilyl telechelic polyolefins from ruthenium-catalyzed cross-metathesis depolymerization of polydienes

“…G2 gave only 3wt% of NF (Table 2, entry 15). Increasing the loading of P3 and 1 generated more NF, yet always as a minor product (< 18wt%; Table 2, entries [15][16][17][18][19][20]. This same trend, yet significantly more pronounced (NF = 23100wt%), was observed with P1, even affording in this case the NF PBD selectively (Table 2, without taking into account any NF) ( Table 2).…”

“…Remarkably, G2 catalyst showed non-optimized TON values up to 24 000, even using commercial (i.e., not purified) grade P3, with well-controlled molar mass values in terms of Mn,theo 49 and Mn,NMR matching (Table 2, entries [15][16][17][18][19][20]. This probably reflects the better purity of initial copolymers.…”

“…18,19 Note that the formation of monofunctional polydiene alongside NF and/or DF, is not expected, inherently to the ROMP mechanism using a symmetrical acyclic alkene CTA, and given the initial low [CTA 1]0/[vinyl]0 ratio and the preliminary cyclization step applied (vide supra) which converts most of these vinyl moieties to generate the cyclooligomers. 50 Thus, CM depolymerization of (purified) P2 generated much more NF PBD than that of (purified) P1 (76wt% vs. 24wt%, Table 2, entries 4,5), in line with the above highlighted lower purity of P2 vs. P1 and the correspondingly less efficient CM.…”

“…18,19,20 The high catalytic productivity (TurnOver Numbers, TONs, up to 90,000 mol(cycloolefin).mol(Ru) 1 ), high selectivity towards bis(trialkoxysilyl) telechelic polyolefins (typically > 85wt%), and low viscosity of the final liquid materials make these industrially relevant adhesive precursors. 21,22,23,24,25,26,27,28 Indeed, in order to ensure effective formulation of adhesives and to maximize contact area and attractive forces between the adhesive and the bonding surface, targeted adhesive polymer precursors should be low viscosity liquids at ambient temperature.…”

Semicrystalline rubber diblock copolymers via cyclooctene ROMP and chain transfer with vinyl-terminated isotactic polystyrene

“…Molecular copolymer architectures are tailored by incorporation of macromonomers, sequenced monomer addition, or by combining ROMP with other polymerization methods . Traditionally, ROMP end group functionalization and ROMP molar mass control are simultaneously achieved by the addition of chain transfer agents (CTAs), among them short acyclic olefins such 1‐octene and 1‐hexene or functionalized olefins, respectively . When using higher molar mass 1‐olefins as macromolecular CTA, ROMP produces diblock copolymers by chain transfer reaction.…”