Ring-opening polymerization of ?-caprolactone and ?-valerolactone using new Sm(III) ?-halo-bis(trimethylsilyl)amido complexes

Abstract

New Sm(III) -halo-bis(trimethylsilyl)amido complexes [Sm(-X) {N(SiMe 3 ) 2 } 2 (THF)] 2 (X ϭ Cl, Br) were synthesized and their crystal structures were analyzed. These complexes were used as catalysts for the homopolymerization of -caprolactone and ␦-valerolactone and found to initiate ring-opening polymerization (ROP) of these monomers in high conversion over a short period, giving homopolymers with a moderate polydispersity index (ϳ 2.0). The effect of temperature and the catalyst amount on the molecular weight distribution was also studied. Mechanistic studies were conducted using 1 : 1 and 1 : 6 molar ratios of -halo-bis-(trimethylsilyl)amido complexes and -caprolactone by 1 H-NMR and 13 C-NMR spectroscopic techniques and revealed the presence of more than one initiating species.

Novel [Sm2I(NPPh3)5(DME)] Initiator for the Living Ring-Opening Polymerization of ε-Caprolactone and δ-Valerolactone

“…Much work has recently focused on rare earth metal complexes for the ROP of lactones. [8][9][10][11] Structurally well-defined lanthanide complexes have attracted increasing attention as initiators for the living polymerization of lactones. [12][13][14] In our earlier work, the new lanthanide initiators based on bis(trimethylsilyl)amido 15,16 and phosphorane iminato 17,18 ligands were synthesized and found to be very active for the ring-opening polymerization of CL.…”

Synthesis of Degradable Materials Based on Caprolactone and Vinyl Acetate Units Using Radical Chemistry

“…[1][2][3][4][5][6][7] A less known route to the formation of poly(caprolactone), first shown by Bailey et al 8 and later followed by some others, 9,10 is by radical ringopening polymerization of 2-methylene-1,3-dioxepane (MDO). 2-methylene-1,3-dioxepane is an interesting cyclic ketene acetal monomer giving poly("-caprolactone) (PCL), on the radical-ring-opening homopolymerization (RROP) and can introduce ester groups onto the vinyl polymer backbones during copolymerizations with vinyl monomers.…”

Ring-Opening Polymerization ofɛ-Caprolactone by Phosphorane Iminato and Cyclopentadienyl Complexes of Rare Earth Elements

“…In a similar manner living chain ends were proved before ROP of CL with Sm-halosilylamido complexes which otherwise showed only moderate polydispersities and no sound correlation of initiator: monomer ratio. [11] An attempt has been made to study the initiation mechanism by carrying out the reaction with molar ratio of 1 : CL = 1 : 10 in NMR tube in C 6 D 6 solvent under inert conditions. In the 13 C NMR spectrum (Figure 3), apart from the many more peaks in the spectrum, peaks at 34.7 ppm (1CH 2 1CO1NPPh 3 ) and at 64.5 ppm (ALa1O1CH 2 1) indicate the cleavage of acyl-oxygen bond and formation of amide end groups.…”

“…This could be accounted to the equilibrium of monomeric and dimeric dysprosium complex as previously discussed for dimeric Sm-halotrimethylsilylamido complexes. [11] …”