To push upper boundaries of effective thermal conductivity in polymer
composites, a fundamental understanding of thermal transport mechanisms is
crucial. Although there is intensive simulation research, systematic
experimental investigation on thermal transport in polymer composites is
limited. To better understand thermal transport processes, we design polymer
composites with perfect fillers (graphite) and defective fillers (graphite
oxide); we choose polar polyvinyl alcohol (PVA) as a matrix model; and we
identify how thermal transport occurs across heterogeneous interfaces. Measured
thermal conductivities of in PVA/defective filler composites is higher than
those of PVA/perfect filler composites, while measured thermal conductivities
in defective fillers are lower than those of perfect fillers. An effective
quantum mechanical model is developed, showing that the vibrational state of
the defective level plays a critical role in enhancing the thermal conductivity
with increased defect concentration. Our experimental and model results have
suggested that defects in polymer composites may enhance thermal transport in
polymer composites by promoting vibrational resonant couplings.Comment: Enclosed: (i) Main Manuscript, including 5 main figures. (ii)
Supplementary Information, including 16 Supplementary Figures and one
self-contained theoretical sectio