Reactivity of Sm(II) compounds as ring-opening polymerization initiators for lactones

Agarwal, Seema; Brandukova-Szmikowski, Natalia E.; Greiner, Andreas

doi:10.1002/(sici)1521-3927(19990501)20:5<274::aid-marc274>3.0.co;2-j

Cited by 19 publications

(14 citation statements)

References 8 publications

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“…In our previous report, both Sm(II) complexes [SmI 2 and Sm(PPh 2 ) 2 ] were examined to compare their relative activity for the ROP of CL 15. Just as reported by Evans and Katsumata,19 SmI 2 showed no reactivity for the polymerization at the ambient temperature over 6 h. However, polymerization occurred in THF at the reflux temperature or, in the case of a low monomer/Sm ratio, with a longer reaction period 20. On the other hand, we found that Sm(PPh 2 ) 2 could initiate the ROP of CL effectively at room temperature, giving polyesters with a higher molecular weight.…”

Section: Resultssupporting

confidence: 77%

“…This decrease in the molecular weight was probably due to transesterification reactions. Similar behavior was observed for the ROP of cyclic esters by other lanthanide catalysts 20, 22…”

Section: Resultssupporting

confidence: 76%

“…With a further increase in this ratio (samples 5 and 6, Table I), the polymer yield, M n , and the weight‐average molecular weight/number‐average molecular weight ratio ( M w / M n ) dropped. The observed molecular weights were not in accordance with the initial monomer/Sm ratio, and this may be ascribed to transesterification reactions or coordinative competition between the active polymer chain end and monomer 20, 21…”

Section: Resultsmentioning

confidence: 95%

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Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

Jiang

Lou

Sun

et al. 2005

J of Applied Polymer Sci

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ABSTRACT:The ring-opening polymerization of -caprolactone initiated with a divalent samarium bis(phosphido) complex [Sm(PPh 2 ) 2 ] is reported. The polymerization proceeded under mild reaction conditions and resulted in polyesters with number-average molecular weights of 8.2 ϫ 10 3 to 12.5 ϫ 10 3 . The yield and molecular weight of poly(-caprolactone)s were dependent on the experimental parameters, such as the monomer/initiator molar ratio, the monomer concentration, the reaction temperature, and the polymerization time. The obtained polymers were characterized with Fourier transform infrared, NMR, gel permeation chromatography, and differential scanning calorimetry. On the basis of an end-group analysis of low-molecular-weight polymers by NMR spectroscopy, a coordination-insertion mechanism is proposed for the polymerization.

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Section: Resultssupporting

confidence: 77%

“…This decrease in the molecular weight was probably due to transesterification reactions. Similar behavior was observed for the ROP of cyclic esters by other lanthanide catalysts 20, 22…”

Section: Resultssupporting

confidence: 76%

Section: Resultsmentioning

confidence: 95%

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Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

Jiang

Lou

Sun

et al. 2005

J of Applied Polymer Sci

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“…SmI 2 initiates ROP of CL only at elevated temperatures or at room temperature in the presence of Sm metal. 26,27 The living character of the polymer chain ends was investigated by block copolymerization CL with VL using 1 (1/CL, 1:150). First, CL was polymerized using 1 as initiator.…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2001

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Ring-opening polymerization of -caprolactone (CL) and δ-valerolactone (VL) was carried out using the initiator system [Sm2I(NPPh3)5(DME)] in the presence of toluene. Experimental molecular weights were in good agreement with the theoretical molecular weights for [CL]0/[1]0 up to 350. Polydispersities are low at 0-20°C but increase at higher temperatures. Addition of small amounts of coordinating solvents such as THF and DME decreased the rate of polymerization and thereby reduced the polydispersity. The active polymer chain ends have been shown by sequential copolymerization of CL and VL, resulting in block copolymers. IntroductionAliphatic polyesters such as PCL and PVL with high molecular weight and narrow molecular weight distribution are of great interest as biodegradable and biocompatible materials. 1-3 Initiators such as aluminum porphyrins, 4 alkylaluminum alkoxides, 5 tin(2-ethyl-hexanoate), 6 and transition metal 7 complexes have been developed for the ring-opening polymerization of lactones. Transesterification reactions either intermolecular with concomitant broadening of the polydispersity or intramolecular, leading to the formation of macrocycles or depolymerization, are inevitable with most of these initiators. 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. Polymerizations of CL initiated by the above-mentioned lanthanide initiators yielded always PCL of moderate polydispersities. This moderate polydispersities were mainly attributed to the faster rate of polymerization than initiation. The polymerizations of CL using these lanthanide initiators followed the scheme of a coordination-insertion mechanism. Further, the insolubility of triphenylphosphorane iminato ligand based initiators in toluene led to higher molecular weight than expected theoretically. Addition of coordinating solvents such as THF and DME increased the solubility of the initiators and decreased the rate of polymerization considerably. Taking into consideration the solubility of the initiators, new initiators based on the phosphorane iminato ligands were prepared in DME, to ensure the presence of DME inside the initiator system. 17 This paper reports results of the initiation of the new samarium complex [Sm 2 I(NPPh 3 ) 5 (DME)] (1) for the controlled synthesis of PCL and PVL. The active chain ends of the living polymer were determined by block copolymerization of CL and VL.

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“…[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.…”

mentioning

confidence: 97%

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

et al. 2009

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Present studies are carried out with an aim to make degradable materials based on caprolactone and vinyl acetate units using radical chemistry. Radical ring-opening copolymerization of 2-methylene-1,3-dioxepane (MDO) with vinyl acetate in presence of AIBN initiator at 70 C was carried out to achieve the aim. The copolymerization introduced degradable PCL repeat units onto the C-C backbone of poly(vinyl acetate). Microstructure analysis of the copolymers is done using different 1D and 2D NMR techniques. Complete ring-opening polymerization of MDO to give ester units was observed during copolymerizations. Reactivity ratios were found out by Kelen Tüdos method and were r VAc ¼ 1:53 and r MDO ¼ 0:47 leading to statistical introduction of ester linkages onto the polymer backbone. The materials showed varied glass transition temperatures (from 37 to À44 C) depending upon the amount of ester linkages and very high elongations. The hydrolysis products were also tested for cytotoxicity studies in L929 cells and compared with that of known and accepted standard materials like poly(ethyleneimine). The hydrolysed products were non toxic and showed a cell viability > 95%. Keeping in view the combined properties like degradability, non-toxicity and low glass transition temperatures, the resulting materials could therefore be proposed for different applications like degradable gums, coatings etc.KEY WORDS: Radical Ring-Opening Polymerization / Polymer Synthesis / Degradable Polymers / Characterization / Ring-opening polymerization of "-caprolactone using anionic or metal catalysts is conventionally used for the synthesis of polycaprolactone (PCL), a well studied and in-demand degradable aliphatic polyester.1-7 A less known route to the formation of poly(caprolactone), first shown by Bailey et al. 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. The careful examination of 13C and 1 H NMR spectra by us 11 showed the occurrence of 100% ring-opening polymerization but the presence of about 9% branched structures in the resulting homopolymer obtained by RROP of MDO. This method of making ester linkages could be very well utilized for introducing degradability onto the nondegradable vinyl polymer backbones by copolymerizations. Also, the homopolymerization and copolymerization behaviour of different cyclic ketene acetals with some vinyl monomers like MMA, vinyl anisole, styrene etc. is reported by us 11-18 and others. 10,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] The main problem during the copolymerization is the huge reactivity difference between the CKA and the vinyl monomers leading to either low molecular weight homo vinyl polymers without ester linkages or copolymers incorpor...

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Reactivity of Sm(II) compounds as ring-opening polymerization initiators for lactones

Cited by 19 publications

References 8 publications

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

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

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

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Reactivity of Sm(II) compounds as ring-opening polymerization initiators for lactones

Cited by 19 publications

References 8 publications

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

Ring‐opening polymerization of ε‐caprolactone with a divalent samarium bis(phosphido) complex

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

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

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