Polycarbonate polyol compositions and methods
In one aspect, the present disclosure encompasses polymerization systems for the copolymerization of CO 2 and epoxides comprising 1) a catalyst including a metal coordination compound having a permanent ligand set and at least one ligand that is a polymerization initiator, and 2) a chain transfer agent having two or more sites that can initiate polymerization. In a second aspect, the present disclosure encompasses methods for the synthesis of polycarbonate polyols using the inventive polymerization systems. In a third aspect, the present disclosure encompasses polycarbonate polyol compositions characterized in that the polymer chains have a high percentage of —OH end groups and a high percentage of carbonate linkages. The compositions are further characterized in that they contain polymer chains having an embedded polyfunctional moiety linked to a plurality of individual polycarbonate chains.
1. A polymerization system for the copolymerization of CO 2 and epoxides, the system comprising:
a metallosalenate metal complex; and
a chain transfer agent having a plurality of sites capable of initiating copolymerization of epoxides and CO 2 ;
wherein the chain transfer agent has a structure Y-A-(Y) n ,
where:
each —Y group is independently a functional group capable of initiating chain growth of epoxide CO 2 copolymers and each Y group may be the same or different;
-A- is a covalent bond or a multivalent moiety; and
n is an integer between 1 and 10, inclusive.
2. A method for the synthesis of aliphatic polycarbonate polyols having a high percentage of —OH end groups, the method comprising the steps of:
a) contacting a reaction mixture comprising one or more epoxides with a polymerization system of claim 1 in the presence of carbon dioxide, wherein the molar ratio of metal complex to epoxide ranges from about 1:100 to about 1:1,000,000;
b) allowing the polymerization reaction to proceed until a desired molecular weight aliphatic polycarbonate polyol has formed, wherein in the aliphatic polycarbonate polyol composition, at least 90% of the end groups are hydroxyl groups; and
c) terminating the polymerization.
3. An aliphatic polycarbonate polyol composition comprising an epoxide-CO 2 copolymer characterized in that the copolymer has:
an Mn between about 400 and about 20,000,
greater than 90% carbonate linkages, and
at least 98% of the end groups are hydroxyl groups.
4. The polycarbonate polyol composition of claim 3 , comprising greater than 95% carbonate linkages.
5. The polycarbonate polyol composition of claim 3 , having an Mn between about 500 and about 5,000 g/mol.
6. The polycarbonate polyol composition of claim 3 comprising polymer chains denoted P 1 having the formula T-Y-A-(Y-T), wherein:
each -T is a polycarbonate chain having a formula independently selected from the group consisting of:
wherein:
E is an optionally substituted C 2 unit derived from an epoxide, where E may represent a monomer unit derived from one type of epoxide, or a mixture of two or more types of epoxide, and
p ranges from about 5 to about 10,000
each —Y group is independently a functional group capable of initiating chain growth of epoxide CO 2 copolymers and each Y group may be the same or different,
-A- is a covalent bond or a multivalent moiety; and
n is an integer between 1 and 10 inclusive.
7. The polycarbonate polyol composition of claim 6 , further comprising polymer chains denoted P 2 having a formula selected from the group consisting of:
wherein
X is a bound form of an anion capable of initiating only one polymer chain.
8. The polycarbonate polyol composition of claim 6 , further comprising polymer chains denoted P 1a having a formula:
9. The polycarbonate polyol composition of claim 6 , wherein each E is
where, R 21 , R 22 , R 23 , and R 24 , are each independently selected from the group consisting of: —H; and an optionally substituted group selected from C 1-30 aliphatic; C 6-14 aryl; 3- to 12-membered heterocycle, and 5- to 12-membered heteroaryl, where any two or more of R 21 , R 22 , R 23 , and R 24 can be taken together with intervening atoms to form one or more optionally substituted 3- to 12-membered rings, optionally containing one or more heteroatoms.
10. The polycarbonate polyol composition of claim 9 , wherein -E- comprises predominantly —CH 2 CH 2 — units derived from ethylene oxide, or wherein -E- comprises predominantly —CH 2 CH(CH 3 )— groups derived from propylene oxide.
11. The polycarbonate polyol composition of claim 6 , where chains of type P 1 have the formula:
wherein each z is independently 0 or 1.
12. A polyurethane composition formed by reaction of one or more isocyanates with an aliphatic polycarbonate polyol of claim 3 .
13. An article of manufacture comprising an aliphatic polycarbonate polyol composition of claim 3 .
14. The polyurethane composition of claim 12 , wherein the composition comprises a foam or coating.
15. The polycarbonate polyol composition of claim 6 , wherein at least 99% of the end groups of the polycarbonate polyol are OH groups.
16. The polycarbonate polyol composition of claim 6 , wherein the PDI of the polycarbonate polyol is less than 1.6.
17. The polycarbonate polyol composition of claim 6 , wherein the PDI of the polycarbonate polyol is less than 1.2.
18. The polycarbonate polyol composition of claim 6 , wherein the Y-A-(Y) n moiety is derived from a chain transfer agent selected from a polyhydric alcohol, a polycarboxylic acid, or a hydroxy acid.
19. The polycarbonate polyol composition of claim 6 , wherein the Y-A-(Y) n moiety is derived from a chain transfer agent, wherein at least one Y group is a carboxylic acid and one or more additional Y groups are —OH.
20. The polymerization system of claim 1 , wherein the metallosalenate metal complex is a cobalt salen complex.