Polymer matrices functionalized with liquid crystals for enhanced thermal conductivity

1. A thermal interface material comprising a polymer matrix functionalized with liquid crystals grafted onto the polymer matrix, and at least one thermally conductive filler in the polymer matrix, wherein the thermal interface material has a thermal conductivity of at least 1 Watt per meter Kelvin.

2. The thermal interface material of claim 1 , wherein the liquid crystals are grafted onto siloxane chains of the polymer matrix.

3. The thermal interface material of claim 1 , wherein the liquid crystals comprise liquid crystalline units grafted onto siloxane chains of the polymer matrix.

4. The thermal interface material of claim 1 , wherein:

the polymer matrix comprises a silicone matrix; and

the liquid crystalline units are grafted onto silicone chains of the silicone matrix.

5. The thermal interface material of claim 1 , wherein the thermal interface material includes liquid crystalline domains in an amorphous silicone matrix.

6. The thermal interface material of claim 5 , wherein the liquid crystalline domains in the amorphous silicone matrix have a lamellar ordering.

7. The thermal interface material of claim 1 , wherein the at least one thermally conductive filler has a thermal conductivity of at least 1 Watt per meter Kelvin.

8. A thermally conductive composite comprising a polymer matrix functionalized with liquid crystals grafted onto the polymer matrix, and at least one thermally conductive filler in the polymer matrix, wherein the thermally conductive composite includes a reaction product of cholesteryl oleate and the polymer matrix.

9. A thermally conductive composite comprising a polymer matrix functionalized with liquid crystals grafted onto the polymer matrix, and at least one thermally conductive filler in the polymer matrix, wherein cholesteryl oleate grafts are on a siloxane backbone of the polymer matrix and/or the liquid crystals comprise cholesteryl oleate liquid crystalline units grafted onto silicone chains of the silicone matrix.

10. A thermally conductive composite comprising a polymer matrix functionalized with liquid crystals grafted onto the polymer matrix, and at least one thermally conductive filler in the polymer matrix, wherein:

the polymer matrix comprises a two-part silicone matrix including polydimethylsiloxane (PDMS) chains and vinyl-terminated PDMS chains; and

the liquid crystals are attached to vinyl-terminated PDMS chains.

11. A thermal interface material including the thermally conductive composite of claim 10 , wherein the thermal interface material has a thermal conductivity of at least 1 Watt per meter Kelvin.

12. The thermal interface material of claim 1 , wherein:

functionalization of the polymer matrix with liquid crystals enhances thermal conductivity while retaining deflection and electrical insulation properties such that the functionalized polymer matrix is thermally conductive and dielectric; and/or

functionalization of the polymer matrix with liquid crystals enhances thermal conductivity without having to increase a loading amount of thermally conductive filler in the polymer matrix.

13. A conformable thermal interface material including a thermally conductive composite comprising a polymer matrix functionalized with liquid crystals grafted onto the polymer matrix, and a least one thermally conductive filler in the polymer matrix, whereby the conformable thermal interface material is suitable for use to fill a gap between at least two surfaces to transfer heat between the at least two surfaces, and wherein:

the at least one thermally conductive filler comprises one or more of metal particles, ceramic particles, carbon-containing species fibers, graphite, graphene, carbon nanotubes, boron nitride, aluminum, aluminum oxide, alumina trihydrate, and zinc oxide; and/or

the at least one thermally conductive filler has a thermal conductivity of at least 1 Watt per meter Kelvin.

14. A method comprising modifying liquid crystals and incorporating the modified liquid crystals into a polymer matrix, such that the modified liquid crystals are grafted onto the polymer matrix, and adding at least one thermally conductive filler in the polymer matrix, wherein:

the liquid crystals comprise cholesteryl ester based liquid crystalline units; and

the at least one thermally conductive filler comprises one or more of metal particles, ceramic particles, carbon-containing species, fibers graphite, graphene, carbon nanotubes, boron nitride, aluminum, aluminum oxide, alumina trihydrate, and zinc oxide; and/or the at least one thermally conductive filler has a thermal conductivity of at least 1 Watt per meter Kelvin.

15. The method of claim 14 , wherein the method includes grafting liquid crystalline units onto siloxane chains of the polymer matrix, and wherein the at least one thermally conductive filler has a thermal conductivity of at least 1 Watt per meter Kelvin.

16. The method of claim 15 ; wherein grafting of the liquid crystalline units onto the siloxane chains of the polymer matrix generates liquid crystalline domains in the amorphous silicone matrix having lamellar ordering.

17. A method comprising modifying liquid crystals and incorporating the modified liquid crystals into a polymer matrix, such that the modified liquid crystals are grafted onto the polymer matrix, and adding at least one thermally conductive filler in the polymer matrix; wherein the method includes using a cross linker attached to liquid crystalline units to decouple the liquid crystalline units from a polymer backbone of the polymer matrix, wherein:

the at least one thermally conductive filler comprises one or more of metal particles, ceramic particles, carbon-containing species, fibers, graphite, graphene, carbon nanotubes, boron nitride, aluminum, aluminum oxide, alumina trihydrate, and zinc oxide; and/or

the at least one thermally conductive filler has a thermal conductivity of at least 1 Watt per meter Kelvin.

18. The method of claim 17 , wherein the method includes using a Si—H group of the cross linker attached to the liquid crystalline units to attach the liquid crystalline units onto silicone chains of a first part of the polymer matrix via a hydrosilation reaction.

19. The method of claim 18 , wherein the method includes annealing the silicone chains with the liquid crystalline units attached thereto.

20. The method of claim 19 , wherein:

the polymer matrix comprises a two-part silicone matrix including polydimethylsiloxane (PDMS) chains and vinyl-terminated PDMS chains;

the liquid crystalline units are attached to the vinyl-terminated PDMS chains; and

the method includes curing the PDMS chains and the vinyl-terminated PDMS chains with the liquid crystalline units attached thereto.

21. The method of claim 17 , wherein

the liquid crystals comprise cholesteryl ester based liquid crystalline units.

22. A method of enhancing thermal conductivity of a polymer matrix, the method comprising modifying liquid crystals and incorporating the modified liquid crystals into the polymer matrix, such that the modified liquid crystals are grafted onto the polymer matrix;

wherein:

the method includes using a cross linker attached to liquid crystalline units to decouple the liquid crystalline units from a polymer backbone of the polymer matrix;

the method includes using a Si—H group of the cross linker attached to the liquid crystalline units to attach the liquid crystalline units onto silicone chains of a first part of the polymer matrix via a hydrosilation reaction;

the method includes annealing the silicone chains with the liquid crystalline units attached thereto;

the polymer matrix comprises a two-part silicone matrix including polydimethylsiloxane (PDMS) chains and vinyl-terminated PDMS chains;

the liquid crystalline units are attached to the vinyl-terminated PDMS chains;

the method includes curing the PDMS chains and the vinyl-terminated PDMS chains with the liquid crystalline units attached thereto;

the annealing occurs at a temperature about 38° C. for about 12 hours; and

curing occurs at about 100° C.