Dual functional linear siloxanes, step-growth polymers derived therefrom, and methods of preparation thereof
View Patent ↗Linear siloxane polymers having low viscosities, precise molecular weights and two distinct polymer termini are provided. Preferred viscosities are greater than 5 cSt and less than 20,000 cSt, and the preferred functionalities at the polymer termini are one hydrogen and one vinyl group, each attached to a silicon atom. Methods for producing such siloxane polymers are also described In the presence of catalysts, such as Pt 0 complexes, these siloxanes undergo step-growth polymerization to form elastomers at temperatures below 150° C.
1. A linear siloxane polymer having one unsaturated group terminus and one hydride group terminus, wherein the siloxane polymer has a degree of polymerization of at least 20 and a polydispersity less than about 1.2, and wherein a ratio of unsaturated group termini to hydride group termini is substantially 1:1.
2. The siloxane polymer according to claim 1 , wherein the degree of polymerization is at least 20 to about 1000.
3. The siloxane polymer according to claim 2 , wherein the degree of polymerization is about 20 to about 200.
4. The siloxane polymer according to claim 1 , wherein the unsaturated group is selected from the group consisting of vinyl, styryl, allyl, methallyl, hexenyl, and octenyl.
5. The siloxane polymer according to claim 1 , wherein the siloxane backbone is selected from the group consisting of diphenylsiloxane, phenylmethylsiloxane, trifluoropropylmethylsiloxane, dimethylsilylethylsiloxane, and alkylmethylsiloxane.
6. The siloxane polymer according to claim 5 , wherein the siloxane backbone is dimethylsiloxane and the unsaturated group is vinyl.
7. The siloxane polymer according to claim 1 , wherein the polymer has a viscosity of about 20 to about 20,000 cSt.
8. The siloxane polymer according to claim 1 , wherein the polymer is isolated from a reaction mixture.
9. A method of forming a monovinyl-monohydride terminated siloxane polymer having a degree of polymerization greater than 6 comprising reacting an alkyl or aryl lithium compound with trivinyltrimethylcyclotrisiloxane to form a lithium vinylalkylmethylsilanolate or lithium vinylarylmethylsilanolate, followed by reaction with a strained cyclic siloxane and termination with a hydride-containing chlorosilane.
10. The method according to claim 9 , wherein the alkyl or aryl lithium compound is selected from the group consisting of methyl lithium, butyl lithium, and phenyl lithium.
11. The method according to claim 9 , wherein the strained cyclic siloxane is selected from the group consisting of hexamethylcyclotrisiloxane; (3,3,3-trifluoropropyl)methylcyclotrisiloxane; 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane; triphenyltrimethylcyclotrisiloxane; and hexaphenylcyclotrisiloxane.
12. The method according to claim 9 , wherein the monovinyl-monohydride terminated siloxane polymer has a polydispersity less than about 1.6.
13. The method according to claim 9 , wherein the hydride-containing chlorosilane is selected from the group consisting of dimethylchlorosilane, phenylmethylchlorosilane, diphenylchlorosilane, and diisopropylchlorosilane.
14. A method of forming a monounsaturated-monohydride terminated siloxane polymer having a degree of polymerization greater than 6 comprising reacting an alkyl or aryl lithium compound with tetramethylcyclotetrasiloxane to form a lithium alkylmethylhydrogensilanolate or lithium arylmethylhydrogensilanolate, followed by reaction with a strained cyclic siloxane and termination with an alkyl- or aryl-methylchlorosilane having an unsaturated functionality.
15. The method according to claim 14 , wherein the unsaturated functionality is vinyl or allyl.
16. The method according to claim 14 , wherein the alkyl or aryl lithium compound is selected from the group consisting of methyl lithium, butyl lithium, and phenyl lithium.
17. The method according to claim 14 , wherein the strained cyclic siloxane is selected from the group consisting of hexamethylcyclotrisiloxane; (3,3,3-trifluoropropyl)methylcyclotrisiloxane; 2,2,5,5-tetramethyl-2,5-disila-1-oxacyclopentane; triphenyltrimethylcyclotrisiloxane; and hexaphenylcyclotrisiloxane.
18. The method according to claim 14 , wherein the monounsaturated-monohydride terminated siloxane polymer has a polydispersity less than about 1.6.
19. A linear elastomeric product having no apparent crosslinking, wherein the product is formed from a linear siloxane polymer having one unsaturated group terminus and one hydride group terminus, wherein the siloxane polymer has a degree of polymerization of at least 20 and a ratio of unsaturated group termini to hydride group termini is substantially 1:1.
20. The elastomeric product according to claim 19 , wherein the linear siloxane polymer is a monovinyl-monohydride terminated polysiloxane.
21. The elastomeric product according to claim 19 , wherein the product is formed via hydrosilylation step-growth polymerization of the linear siloxane polymer.
22. The elastomeric product according to claim 19 , wherein the linear siloxane polymer is uncompounded or compounded with a reinforcing agent or filler.
23. A method of producing an elastomeric product according to claim 19 , comprising reacting the siloxane polymer with a Pt 0 catalyst.
24. The method according to claim 23 , further comprising compounding the siloxane polymer with a filler or reinforcing agent prior to reaction with the Pt 0 catalyst.
25. The method according to claim 24 , wherein the filler is fumed silica.
26. The method according to claim 23 , wherein the linear siloxane polymer is a monovinyl-monohydride terminated polydimethylsiloxane.
27. The method according to claim 23 , wherein the reaction with the catalyst is performed at a temperature of not greater than about 150° C.