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Poly(trimethylene carbonate) from Biometals‐Based Initiators/Catalysts: Highly Efficient Immortal Ring‐Opening Polymerization Processes
Author(s) -
Helou Marion,
Miserque Olivier,
Brusson JeanMichel,
Carpentier JeanFrançois,
Guillaume Sophie M.
Publication year - 2009
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200800788
Subject(s) - chemistry , trimethylene carbonate , ring opening polymerization , polycarbonate , polymerization , monomer , catalysis , metal , polymer chemistry , isopropyl , alkoxide , carbonate , benzyl alcohol , molar mass , lactide , alcohol , medicinal chemistry , organic chemistry , polymer
AbstractThe ring‐opening polymerization (ROP) of trimethylene carbonate (TMC) was evaluated in bulk at 60–110 °C using various catalyst systems based on bio‐friendly metals, including the metal bis(trimethylsilylamides) Mg[N(SiMe 3 ) 2 ] 2 , Ca[N(SiMe 3 ) 2 ] 2 (THF) 2 , Y[N(SiMe 3 ) 2 ] 3 , (BDI)Fe[N(SiMe 3 ) 2 ] [BDI=CH(CMeNC 6 H 3 ‐2,6‐ i‐ Pr 2 ) 2 ], Fe[N(SiMe 3 ) 2 ] 2 , Fe[N(SiMe 3 ) 2 ] 3 , Zn[N(SiMe 3 ) 2 ] 2 , (BDI)Zn[N(SiMe 3 ) 2 ] and ZnEt 2 , associated with an alcohol such as isopropyl or benzyl alcohol. The actual metal alkoxide initiating species has been formed in situ prior to the addition of TMC. Introduction of the alcohol component in excess leads to the “immortal” ring‐opening polymerization (ROP) of TMC. According to such an “immortal” ROP process of TMC, whichever the metal species, as many as 200 polycarbonate chains could be successfully grown from a unique metal center in a well controlled ROP process. The best performances were obtained using the discrete (BDI)Zn[N(SiMe 3 ) 2 ] precursor. Under optimized conditions, as many as 50,000 equivalents of TMC could be fully converted from as little as 20 ppm of this metallic precursor, allowing the preparation of a polytrimethylene carbonate (PTMC) with a molar mass as high as 185,200 g mol −1 with a relatively narrow molar mass distribution ( M w / M n =1.68). A double monomer feed experiment carried out with the (BDI)Zn[N(SiMe 3 ) 2 ]/BnOH initiating system proved the “living” character of the polymerization. Characterization of the PTMCs by NMR and size exclusion chromatography (SEC) showed well‐defined α‐hydroxy‐ω‐alkoxycarbonate telechelic polymers, highlighting the controlled character of this “living and immortal” ROP process. Using the (BDI)Zn[N(SiMe 3 ) 2 ] precursor, varying the alcohol (ROH) to 2‐butanol, 3‐buten‐2‐ol or 4‐(trifluoromethyl)benzyl alcohol, revealed the versatility of this approach, allowing the preparation of accordingly end‐functionalized HO‐PTMC‐OR polymers. The very low initial loading of metal catalyst considerably limits the potential toxicity and thus allows such polycarbonates to be used in the biomedical field.