Synthesis of crystalline polymers from cyclic diolides
View Patent ↗Biodegradable polymers with advantageous physical and chemical properties are described, as well as methods for making such polymers. In one embodiment, a new chemical synthesis route to technologically important biodegradable poly(3-hydroxybutyrate) (P3HB) with high isotacticity and molecular weight required for a practical use is described. The new route can utilize racemic eight-membered cyclic diolide (rac-DL), meso-DL, or a rac-DL and meso-DL mixture, derived from bio-sourced dimethyl succinate, and enantiomeric (R,R)-DL and (S,S)-DL, optically resolved by metal-based catalysts. With a stereoselective racemic molecular catalyst, the ROP of rac-DL under ambient conditions produces rapidly P3HB with essentially perfect isotacticity ([mm]>99%), high crystallinity and melting temperature (T m =171° C.), as well as high molecular weight and low dispersity (M n =1.54×10 5 g/mol, Ð=1.01).
1. A highly isotactic polymer comprising Formula I:
wherein:
n is about 10 to about 10,000;
R is (C 1 -C 18 )alkyl, (C 1 -C 8 )alkenyl, (C 1 -C 8 )alkynyl, benzyl, or aryl; and
Formula I comprises at least 95% isotactic triads with respect to the stereocenters of substituents R on the polymer chain, wherein the at least 95% isotactic triads (mm) have consecutive (R) stereochemical configurations or consecutive (S) stereochemical configurations.
2. The polymer of claim 1 wherein the polymer comprises at least 99% isotactic triads with respect to the stereocenters of substituents R on polymer chain.
3. The polymer of claim 2 wherein the molecular weight M n is at least about 100 kDa.
4. The polymer of claim 1 wherein the polymer has a melting temperature, T m of at least 170° C.
5. A composition comprising polymers of claim 1 wherein the composition comprises approximately equal amounts of polymers having isotactic triads of (R) stereochemical configurations and polymers having isotactic triads of (S) stereochemical configurations.
6. The composition of claim 5 wherein the dispersity index M w /M n of the polymers is less than 1.2.
7. A copolymer comprising a polymer of claim 1 and a polyester of lactone monomers.