Alignment-assisted high thermal conductivity and thermal anisotropy in poly(methyl methacrylate)/graphene nanolaminates

Understanding heat transport at the graphene-polymer (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>Gr</a:mi></a:math>-polymer) interface is the key to improve the thermal conductivity of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>Gr</c:mi></c:math>-based nanocomposites. Here, we fabricate poly (methyl methacrylate)/graphene (PMMA/<e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>Gr</e:mi></e:math>) nanolaminates and find an ultrahigh increase of the in-plane thermal conductivity (8.9 ± 0.9 W<g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:msup><g:mrow><g:mrow><g:mi mathvariant="normal">m</g:mi></g:mrow></g:mrow><g:mrow><g:mo>−</g:mo><g:mn>1</g:mn></g:mrow></g:msup><g:msup><g:mrow><g:mrow><g:mi mathvariant="normal">K</g:mi></g:mrow></g:mrow><g:mrow><g:mo>−</g:mo><g:mn>1</g:mn></g:mrow></g:msup></g:math>) compared to net PMMA and the thermal conductivity anisotropy (approximately equal to 53) at low <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mi>Gr</k:mi></k:math> loading (1 vol. %). The strong anisotropic thermal conduction can be attributed to the predominantly in-plane oriented <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mi>Gr</m:mi></m:math> nanoflake and, intriguingly, the graphene-induced planar alignment of PMMA in the proximity of <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>Gr</o:mi></o:math>, as revealed by polarized infrared spectroscopic (-IR) imaging, nano-FTIR and IR s-SNOM. We demonstrated the contribution of interface-induced confinement to the observed thermal property, providing deeper insights into heat transport at the <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mi>Gr</q:mi></q:math>-polymer interface.