Flexible effective heat transport composites for thermal interface applications
Disclosed herein is a composite material comprising a crosslinked polymeric matrix, the crosslinked polymeric matrix formed from a polymeric material comprising a plurality of carboxylic acid functional groups and a plurality of liquid metal particles having a surface functionalized with a plurality of amino and/or hydroxyl functional groups, where the plurality of liquid metal particles and the polymeric material are covalently bonded together by a plurality of amide and/or ester bonds formed from the plurality of carboxylic acid functional groups and the plurality of amino and/or hydroxyl functional groups. Also disclosed herein is a thermal interface layer using said composite material and a thermoelectric device also using said composite material.
1 . A composite material comprising a crosslinked polymeric matrix, the crosslinked polymeric matrix comprising:
a polymeric material comprising a plurality of carboxylic acid functional groups; and
a plurality of liquid metal particles having a surface functionalized with a plurality of amino and/or hydroxyl functional groups, wherein
the plurality of liquid metal particles and the polymeric material are covalently bonded together by a plurality of amide and/or ester bonds formed from the plurality of carboxylic acid functional groups and the plurality of amino and/or hydroxyl functional groups.
2 . The composite material according to claim 1 , wherein the polymeric material is a polyalkylcarboxylic acid siloxane.
3 . The composite material according to claim 2 , wherein the polyalkylcarboxylic acid siloxane has a repeating unit according to formula I:
where R 1 is a C 1 to C 6 alkyl group that is unbranched or branched.
4 . The composite material according to claim 1 , wherein the polymeric material has a number average molecular weight of from 700 to 5000 g/mol.
5 . The composite material according to claim 1 , wherein the plurality of liquid metal particles have a surface functionalized by a block copolymer moiety formed from formula II and/or formula III:
where
n, n′, m and m′ refer to the repeating units of the block copolymer moiety; and the wavy line refers to the point of attachment to the surface of the liquid metal particles to which the block copolymer moiety is attached.
6 . The composite material according to claim 5 , wherein the number average molecular weight of the block copolymer moiety is from 5,000 to 20,000 g/mol.
7 . The composite material according to claim 1 , wherein the plurality of liquid metal particles having a surface functionalized with a plurality of amino and/or hydroxyl functional groups have an average particle size of from 50 nm to 50 μm.
8 . The composite material according to claim 1 , wherein the liquid metal in the plurality of liquid metal particles having a surface functionalized with a plurality of amino functional groups is selected from one or more of the group consisting of EGaIn, EGaInSn, EGaInSnZn, ECsIn, ECsInSn, ECsInZn.
9 . The composite material according to claim 1 , wherein the plurality of liquid metal particles form from greater than 20 to 50 vol % of the composite material's volume.
10 . The composite material according to claim 1 , wherein the plurality of liquid metal particles are provided having a close packed arrangement within the composite material.
11 . The composite material according to claim 1 , wherein the composite material has a thermal conductivity of from 1.0 to 1.5 κ(W/mK).
12 . The composite material according to claim 1 , wherein, when:
(i) the plurality of liquid metal particles having a surface functionalized with a plurality of amino and/or hydroxyl functional groups have an average particle size of from 50 nm to 1 μm; and
(ii) the composite material is formed as a cuboidal film with a length and a width, where the width is smaller in dimension than the length, the composite material has:
(ai) a thermal conductivity under a strain perpendicular to the length of the cuboidal film that is greater than a thermal conductivity of the same cuboidal film when under no strain; and/or
(aii) a thermal conductivity under a strain parallel to the length of the cuboidal film that is less than or equal to a thermal conductivity of the same cuboidal film when under no strain.
13 . The composite material according to claim 1 , wherein, when:
(ia) the plurality of liquid metal particles having a surface functionalized with a plurality of amino and/or hydroxyl functional groups have an average particle size of from greater than 1 to 50 μm; and
(iia) the composite material is formed as a cuboidal film with a length and a width, where the width is smaller in dimension than the length, the composite material has:
(bi) a thermal conductivity under a strain parallel to the length of the cuboidal film that is greater than a thermal conductivity of the same cuboidal film when under no strain; and/or
(bii) a thermal conductivity under a strain perpendicular to the length of the cuboidal film that is less than or equal to a thermal conductivity of the same cuboidal film when under no strain.
14 . The composite material according to claim 1 , wherein the plurality of liquid metal particles having a surface functionalized with a plurality of amino and/or hydroxyl functional groups have a surface functionalized with a plurality of amino functional groups.
15 . A thermal interface layer comprising a composite material according to claim 1 and n- and p-type thermoelectric legs.
16 . A deformable thermoelectric device comprising a composite material according to claim 1 .
17 . The deformable thermoelectric device according to claim 16 , where the thermoelectric device comprises a thermal interface layer comprising the composite material according to claim 1 and n- and p-type thermoelectric legs.
18 . The deformable thermoelectric device according to claim 16 , wherein when the deformable thermoelectric device has a first surface and a second surface and the plurality of liquid metal particles having a surface functionalized with a plurality of amino and/or hydroxyl functional groups have an average particle size of from 50 nm to 10 μm, then when
a difference in temperature exists between the first surface and the second surface of the deformable thermoelectric device, then a normalized open circuit voltage of the thermoelectric device will increase with an increase in pressure.
19 . The deformable thermoelectric device according to claim 16 , wherein the deformable thermoelectric device is a wearable deformable thermoelectric device.
20 . The deformable thermoelectric device according to claim 16 , wherein the deformable thermoelectric device forms part of one or more of a power device in an antenna, and a deformable device that requires power.