Pan-tactic crystalline and recyclable polythioesters
View Patent ↗A monomer design strategy based on a bridged bicyclic thiolactone that produces stereo-disordered to perfectly stereo-ordered polythioesters is disclosed. The described polythioesters exhibit high crystallinity and full chemical recyclability. Such polymers possess intrinsic tacticity-independent crystallinity and chemical recyclability, tunable tacticities from stereo-disorder to perfect stereoregularity, as well as combined high-performance properties such as high thermal stability and crystallinity, and high mechanical strength, ductility and toughness.
1. A polymer comprising a polythioester represented by Formula I:
wherein
the polythioester is a linear polythioester or a cyclic polythioester; and
n is 20-50,000.
2. The polymer of claim 1 wherein the polythioester is a linear polythioester.
3. The polymer of claim 1 wherein the polythioester is a tactic polythioester.
4. The polymer of claim 3 wherein the tactic polythioester has at least 20% tacticity.
5. The polymer of claim 3 wherein the tactic polythioester has at least 90% tacticity.
6. The polymer of claim 3 wherein the tactic polythioester comprises diads.
7. The polymer of claim 3 wherein the tactic polythioester consists essentially of diads.
8. The polymer of claim 1 wherein the polythioester of Formula I is represented as Formula IIA, IIB, IIC, or IID:
or an enantiomer thereof;
wherein x is 10-25,000.
9. The polymer of claim 8 wherein the polythioester is the threodisyndiotactic polymer of Formula IIA or the erythrodisyndiotactic polymer of Formula IID.
10. A polymer comprising a cyclic polythioester represented as Formula IIIA:
wherein y is 0-10,000.
11. The polymer of claim 10 wherein the cyclic polythioester of Formula IIIA is represented as Formula IIIB:
or an enantiomer thereof.
12. A method for forming the polymer of claim 1 comprising:
a1) contacting a bicyclic thiolactone monomer (M) and catalyst (Cat) to form a cyclic polythioester, wherein the catalyst is a metal-based catalyst or organic N-heterocyclic carbene (NHC); or
a2) contacting the bicyclic thiolactone monomer, catalyst, and an initiator to form a linear polythioester, wherein the catalyst is an organic base and the pKa of the organic base is about 12 to about 42;
wherein the monomer undergoes a polymerization reaction; and
b) quenching the polymerization reaction in step a1) or step a2);
wherein the ratio of M and Cat expressed as a ratio of their concentrations [M]/[Cat] is about 100/1 or greater, and the polymer is thereby formed.
13. The method of claim 12 wherein the bicyclic thiolactone monomer is 2-thiabicyclo[2.2.1] heptan-3-one ( [221] BTL).
14. The method of claim 12 wherein the method comprises step a1) and step b) and the catalyst is tris[N,N-bis(trimethylsilyl)amide]lanthanum (III) (La—N) or 1,3-bis(2,4,6-trimethylphenyl) imidazol-2-ylidene (IMes); or
the method comprises step a2) and step b) and the catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), tris[N,N-bis(trimethylsilyl)amide]lanthanum (III) (La—N), or 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylid-enamino]-2λ 5 ,4λ 5 -catenadi (phosphazene) ( t Bu-P 4 ), and the initiator is an alcohol.
15. The method of claim 12 wherein the polymer formed is crystalline and has a melting-transition temperature (T m ) of about 150° C. to about 250° C.
16. A method for depolymerizing a polythioester comprising contacting the polythioester according to claim 1 and a catalyst at about 10° C. to about 120° C., wherein the polythioester is depolymerized to the parent bicyclic thiolactone monomer wherein the parent is 2-thiabicyclo[2.2.1]heptan-3-one ( [221] BTL).