Description:
Two novel reactions that, when paired, yield an effective, metal-free, one-pot process to produce isotactic poly(L-lactide) from the meso-lactide waste product of conventional poly(lactide), or PLA, production. May be utilized to either improve i-PLLA yield or to produce value-added side product (racemic mixture of L- and D- lactide).
At a Glance:
The invention provides a new method to utilize the “waste” side-product of the industrial L-lactide (L-LA) production process, meso-lactide (meso-LA), by transforming it into the valuable monomer racemic lactide (rac-LA), or directly into crystalline isotactic polylactide (it-PLA)
Some advantages of this invention include quantitative racemization, high enantioselectivity in the kinetic resolution polymerization
Potential commercial applications include the packaging, microelectronics and biomedical fields
Background:
Poly(lactide) (PLA) is one of the most commercially important biodegradable and biocompatible polymers, with a wide array of applications. Crystalline isotactic PLA (it-PLA) is produced by either ring-opening polymerization (ROP) of S,S-lactide (L-LA) to isotactic poly(L-lactide) (PLLA), or the stereoselective ROP of rac-LA by metal-based catalysts or initiators. The emerging organopolymerization of LA offers a metal-free alternative to the PLA products that are free of residual metal contaminates as desired for biomedical or microelectronic applications. The stereoselective organopolymerization of rac-LA has been achieved by a phosphazene superbase and bulky N-heterocyclic carbenes (NHCs) at low temperatures, and enantioseletive or kinetic resolution polymerization of rac-LA by chiral organic catalysts has also been made possible by a cinchona alkaloid and chiral phosphoric acids.
Technology Overview:
The invention provides a new method to utilize the “waste” side-product of the industrial L-lactide (L-LA) production process, meso-lactide (meso-LA), by transforming it into the valuable monomer racemic lactide (rac-LA), or directly into crystalline isotactic polylactide (it-PLA). The epimerization of meso-LA to rac-LA can be achieved by use of a variety of Lewis Pairs, typically in a catalytic amount, either in solution or in a bulk melt. Isotactic polylactide can then be readily prepared using kinetic resolution by organic catalysts. The invention also provides a method to epimerize meso-lactide into racemic lactide comprising contacting meso-lactide and a Lewis acide/base pair for a period of time sufficient to epimerize meso-lactide to racemic lactide.
Benefits:
Metal-free alternative to traditional methods
Quantitative racemization
