Metathetic Selective Degradation of Polyisoprene: Low‐Molecular‐Weight Telechelic Oligomer Obtained from Both Synthetic and Natural Rubber

Abstract

Summary: Degradation studies of cis‐1,4‐polyisoprene were carried out using first and second generation Grubbs catalysts to achieve end‐functionalized acetoxy oligomers in both an organic solvent and a latex phase at room temperature. Well‐defined acetoxy telechelic polyisoprene structures were obtained in a selective manner with a range of $\overline M _{\rm n}$ from 10 000 to 30 000, with a polydispersity index of around 2.5.

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

“…Similarly, CM depolymerization of polyisoprene or rubbers (natural or synthetic) in organic solvents or ionic liquids 39 using a CTA such as 4-octene, 37 or difunctionalized ones such as cis-1,4-diacetoxy-2-butene, cis-but-2-ene-1,4-diol or a bis(trithiocarbonyl) derivative, successfully gave the corresponding telechelic polymers in very good yields (up to 98%) with a good control of molar masses. 39,40,41,42 Also, scrambling CM reactions between PBD or PIP and olefincontaining polyurethanes resulted in hybrid polyolefin/polyurethane materials with compositions ranging from multiblock to random and displaying enhanced mechanical properties.…”

Degradation of non-vulcanized natural rubber renewable resource for fine chemicals used in polymer synthesis

“…This reaction is induced by a wide range of transition metal complexes, but most important and practical catalysts are based on tungsten, molybdenum or rhenium with either tin or aluminum alkyl compound as co-catalyst [22,[58][59][60][61][62][63] . Relatively few reports exist on the metathesis reactions of natural rubber, NR, or poly(cis-1,4-isoprene), IR [22,[58][59][60][61][62][63] . This may be explained by the fact that NR is a very sensitive to the side reactions and this polymer with trisubstituted unsaturations degrades much slower than poly(cis-butadiene) and other polyalkenamers with disubstituted unsaturations [58] .…”

“…Telechelic oligomers can be synthesized by selective cleavage of polymer chain with synchronous functionalization of isoprene units. Solanky with co-workers [22] first investigated a model polymer degradation reaction using Grubbs catalysts [64] to achieve low molar mass telechelic isoprenic oligomers from synthetic polyisoprene and then extended the reaction to high molar mass natural rubber in order to evaluate the efficiency of these catalysts in the latex. First attempts with synthetic polyisoprene were performed in an organic solvent (dichloromethane) using bis(tricyclohexylphosphine)benzylidine ruthenium(IV), a first generation Grubbs catalyst, and cis-but-2-ene-1,4-diol as chain transfer agent (CTA).…”

“…These attempts were not successful in the range of [Isoprene]/[CTA] ratio from 20 to 200. The authors [22] explained this failure of the metathesis reaction under the conditions applied by a slow efficiency of the first generation Grubbs catalyst towards tri-substituted alkenes. Then the process was fulfilled in the same conditions but using tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene] benzylidine ruthenium(IV) dichloride, second generation of Grubbs catalyst.…”

“…In addition, the FTIR spectrum presented a strong peak centered at 1,741 cm -1 corresponding to the carbonyl stretching. Authors [22] proposed the chemical structure of the product as follows (Scheme 3):…”