Stereocontrolled lactide polymerisation determined by the nuclearity of the yttrium initiator.
نویسندگان
چکیده
Two very rapid yttrium initiators for lactide polymerisation are reported; the nuclearity (monomer vs. dimer) of the initiator controls the stereochemistry of the polylactide produced.
منابع مشابه
Studies on the mechanism of the lactide polymerization with highly active zinc guanidine catalysts
Polylactide (PLA) is a biodegradable polyester which is able to replace petrochemical based plastics in many fields [1]. It is commonly produced by ring-opening polymerisation (ROP) of the cyclic diester lactide with metal containing initiator systems using anionic ligand systems [2]. Zinc complexes with neutral guanidine ligands have proven to be highly active initiators in the ROP of lactide ...
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Lewis acidic yttrium(III) and titanium(IV) derivatives of anionic, metal-tethered carbenes apparently act as bifunctional catalysts for the polymerisation of D,L-lactide, using a combination of Lewis acid and base functionalities to initiate ring opening of the cyclic monomer; the alcohol- and amino-functionalised carbenes from which they derive provide models for the first insertion step, and ...
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Dicationic, zwitterionic and "conventional" yttrium compounds act as catalysts for the primary or secondary amine-initiated immortal ROP of rac-lactide; amine-terminated, highly heterotactic poly(rac-lactides) with narrow polydispersities and well-controlled molecular weights are prepared in this manner.
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New opportunities, provided by the 2,2'-[1,1'-binaphthyl-2,2'-diylbis(nitrylomethilidyne)]diphenol (SB(OH)2)/Al(OiPr)3/racemic lactide (rac-LA) polymerization system, employing a combination of stereoelection with (S) and (R) ligand-exchange mechanism at Al-alkoxide active centers were explored. The stereoelectivity was comparable to that determined for the process with an additional synthetic ...
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Seven bis(pyrrolylaldiminato)aluminum methyl complexes were synthesized from the reactions of AlMe3 and two equiv. of the corresponding pyrrolylaldimine ligands. The ligands were modified to have different steric hindrances (C6H5 (1), 2,6-Me2C6H3 (2), 2,4,6-Me3C6H2 (3), 2,6-Et2C6H3 (4) and 2,6-(i)Pr2C6H3 (5)) and electronic contributions (4-CF3C6H4 (6) and 4-OMeC6H4 (7)). Crystal structures of ...
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ورودعنوان ژورنال:
- Chemical communications
دوره 27 شماره
صفحات -
تاریخ انتشار 2009