Unlocking the Potential of Imperfections in High-Performance Materials

A research team led by the University of Massachusetts Amherst has found that imperfections can offer advantages in the development of new materials for modern devices. These materials are designed to be lightweight, flexible, and efficient at dissipating heat.

According to the study's theoretical and experimental results, polymers made with thermally conductive fillers that contained imperfections outperformed those with perfect fillers by 160 %. This unexpected finding challenges the long-held belief that imperfections reduce material performance, suggesting an alternative approach to creating polymer composites with high heat conductivity.

The investigation, led by UMass Amherst, was supported by the Massachusetts Institute of Technology, North Carolina State University, Stanford University, Oak Ridge National Laboratory, Argonne National Laboratory, and Rice University.

Polymers are widely used in modern technology due to their lightness, electrical insulation, flexibility, and ease of manufacturing—attributes that metals and ceramics cannot match. These materials are found in devices such as high-speed microchips, LEDs, cellphones, and soft robots.

However, most common polymers are thermal insulators with low thermal conductivity, which can lead to overheating. Their insulating properties trap heat, creating hot spots that degrade performance, increase wear, and elevate the risk of failures and fires.

To address this issue, scientists have sought to improve polymer heat conductivity by adding highly thermally conductive fillers, such as metals, ceramics, or carbon-based compounds. The idea is simple: adding these fillers should improve the material’s thermal performance.

However, the results have not always been as expected. For instance, a polymer mixed with diamond, which has a high thermal conductivity of about 2,000 watts per meter per kelvin (W m^-1 K^-1), might theoretically achieve conductivity around 800 W m^-1 K^-1 with 40 % diamond filler. In practice, challenges such as filler clumping, defects, high contact resistance between fillers and polymers, and the low thermal conductivity of the polymer matrix have hindered heat transfer.

Understanding thermal transport mechanisms in polymeric materials has been a long-standing challenge, partly due to the complicated polymer structures, ubiquitous defects, and disorders.

Yanfei Xu, Study Corresponding Author and Assistant Professor, Mechanical and Industrial Engineering, University of Massachusetts Amherst

The researchers developed two polymer composites using polyvinyl alcohol (PVA) at low volume fractions of 5 % each: one with perfect graphite fillers and the other with defective graphite oxide fillers. Their goal was to establish a foundation for understanding thermal transport in polymeric materials and managing heat transfer across heterogeneous interfaces.

As expected, the ideal fillers were more thermally conductive than the imperfect ones.

We measured perfect fillers (graphite) on their own have high thermal conductivity of roughly 292.55 W m^-1 K^-1 compared to only 66.29 W m^-1 K^-1 for defective ones (graphite oxide) on their own–a nearly fivefold difference.

Yijie Zhou, Study Lead Author and Mechanical Engineering Graduate Student, University of Massachusetts Amherst

However, unexpectedly, polymers with defective graphite oxide fillers outperformed those with perfect graphite fillers by 160 % when these fillers were introduced.

To understand how defects affect thermal transport in polymer composites, the researchers used a combination of experiments and models, including neutron scattering, thermal transport measurements, quantum mechanical modeling, and molecular dynamics simulations.

They found that the defective fillers enhance heat transmission because their irregular surfaces prevent polymer chains from packing as densely as they would with perfectly smooth fillers. This result, referred to as improved vibrational coupling between the polymers and defective fillers at the polymer/filler interfaces, leads to increased thermal conductivity and reduced resistance, making the material more efficient at heat transfer.

Defects, at times, act as bridges, enhancing the coupling across the interface and enabling better heat flow. Indeed, imperfection can sometimes lead to better outcomes.

Jun Liu, Associate Professor, Department of Mechanical and Aerospace Engineering, North Carolina State University

Xu believes that these practical and theoretical findings lay the groundwork for developing novel polymeric materials with ultrahigh thermal conductivity. These advancements provide new opportunities for devices, ranging from high-performance microchips to next-generation soft robotics, to operate more efficiently with improved heat dissipation.

Journal Reference:

Zhou, et al. (2025) Defects vibrations engineering for enhancing interfacial thermal transport in polymer composites. Science Advances. doi/10.1126/sciadv.adp6516