A quick stretch switches this polymer’s capacity to transport heat | MIT News
Stretch‑Activated Polymers: Turning Plastic‑Like Heat Flow into Marble‑Level Cooling
Why thermal conductivity matters
Most everyday materials have a fixed ability to move heat. A marble countertop feels cold because it pulls heat away quickly, while a plastic cutting board feels warm because it does the opposite.
The MIT breakthrough: a quick stretch doubles heat flow
MIT engineers discovered that a common, soft polymer—an olefin block copolymer (OBC)—can switch its thermal conductivity in less than a quarter of a second. When the material is stretched rapidly, its ability to conduct heat more than doubles, moving from a plastic‑like baseline to a level closer to marble. When the stretch is released, the polymer snaps back to its original, low‑conductivity state.
“The resulting difference in heat dissipation through this material is comparable to a tactile difference between touching a plastic cutting board versus a marble countertop,” explains Svetlana Boriskina, principal research scientist at MIT.
How the switch works at the molecular level
In its relaxed form, OBC consists of tangled, amorphous carbon‑hydrogen chains that block heat. A rapid stretch straightens these chains and aligns the few crystalline islands that already exist. This alignment creates temporary “highways” for heat, but the material never fully crystallizes, allowing the process to reverse repeatedly.
“As we stretched and released the material, we realized that its thermal conductivity was really high when it was stretched and lower when it was relaxed, over thousands of cycles,” notes Duo Xu, MIT graduate student and co‑author.
Real‑world possibilities
Smart apparel. Fibers woven into clothing could stay warm under normal conditions, then instantly conduct heat away when the wearer stretches the fabric—providing on‑demand cooling.
Electronics cooling. Laptop chassis or internal heat‑spreaders made from stretch‑responsive OBC could adjust their conductivity in real time, protecting chips from thermal overload.
Building infrastructure. Wall panels or roofing materials that react to mechanical strain (e.g., from wind or thermal expansion) could self‑regulate temperature, reducing HVAC loads.
From spandex alternatives to heat‑switching heroes
The team originally sought a recyclable replacement for spandex, exploring polyethylene fibers. During those experiments they noticed the unexpected heat‑switching behavior of OBC, leading to the current focus on reversible thermal conductivity.
Future directions
Researchers are now modelling how to amplify the conductivity jump—from plastic‑like toward the extraordinary levels of diamond. Achieving such a leap could have “huge industrial and societal impact,” according to Boriskina.
Read more
- Full study in Advanced Materials
- MIT’s earlier work on crystalline polyethylene
- Thermal Materials Overview (internal)
Frequently Asked Questions
- Can the thermal switch be used many times?
- Yes. The OBC material has been tested over thousands of stretch‑release cycles with consistent conductivity changes.
- Is the material still mostly amorphous when stretched?
- Correct. The polymer remains largely amorphous; only the existing crystalline domains align temporarily.
- What is the speed of the conductivity change?
- The switch from low to high conductivity occurs within 0.22 seconds of a rapid stretch.
- Could this technology replace traditional heat‑sinks?
- Potentially. If the conductivity boost can be scaled, stretch‑responsive polymers could complement or replace static metal heat‑sinks in adaptive systems.
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