Zhou Jingyi, Chen Chen, Sun Jinchi, Fielitz Thomas R, Zhou Weijun, Cahill David G, Braun Paul V
Department of Materials Science and Engineering, Grainger College of Engineering, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA.
Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL, 61801, USA.
Angew Chem Int Ed Engl. 2025 Jun 17;64(25):e202503497. doi: 10.1002/anie.202503497. Epub 2025 Apr 25.
The intrinsic thermal conductivity ( ) of polymers ranges between 0.13 W mK in amorphous polyvinyl chloride to 60 W mK in ultrahigh molecular weight polyethylene. Increasing the amorphous content of polymers to further lower is insufficient as this approach reaches a practical limit at approximately 0.15 W mK. Inspired by the low and low speed of sound of fluorinated liquids, we explored whether this behavior in liquids can be extended to polymers. We synthesized seven partially fluorinated (9%-17% atomic fraction F) and ten conventional polyurethanes. Fluorinated polyurethanes exhibit a reduction in up to 50% compared to their nonfluorinated counterparts. Microstructural analysis revealed that the fluorinated polyurethanes exhibited reduced crystallinity and increased molecular spacing. Furthermore, we observed a decreased speed of sound in fluorinated polymers by forced Brillouin scattering via a new analysis method that captures weak signals from highly scattering semicrystalline polymers. The lowest thermal conductivity, 0.13 W mK at room temperature, was observed in polyurethane synthesized from 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol (16F) and isophorone diisocyanate (IPDI). Our study provides deeper insights into the relationship between , microstructure, and chemical structure, paving the way to rational design of polymers with thermal conductivity below the lowest limit of conventional amorphous polymers.
聚合物的本征热导率（ ）范围在非晶态聚氯乙烯的0.13 W/(m·K)至超高分子量聚乙烯的60 W/(m·K)之间。增加聚合物的非晶态含量以进一步降低热导率并不充分，因为这种方法在约0.15 W/(m·K)时达到实际极限。受含氟液体低热导率和低声速的启发，我们探究了液体中的这种行为是否能扩展到聚合物。我们合成了七种部分氟化（原子分数F为9%-17%）的聚氨酯和十种传统聚氨酯。与非氟化的对应物相比，氟化聚氨酯的热导率降低了高达50%。微观结构分析表明，氟化聚氨酯的结晶度降低，分子间距增大。此外，通过一种新的分析方法，即捕获来自高散射半结晶聚合物的微弱信号的强迫布里渊散射，我们观察到氟化聚合物中的声速降低。在由2,2,3,3,4,4,5,5-八氟-1,6-己二醇（16F）和异佛尔酮二异氰酸酯（IPDI）合成的聚氨酯中，观察到室温下最低热导率为0.13 W/(m·K)。我们的研究为热导率、微观结构和化学结构之间的关系提供了更深入的见解，为合理设计热导率低于传统非晶态聚合物最低极限的聚合物铺平了道路。
