Shanker Apoorv, Li Chen, Kim Gun-Ho, Gidley David, Pipe Kevin P, Kim Jinsang
Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2800, USA.
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA.
Sci Adv. 2017 Jul 28;3(7):e1700342. doi: 10.1126/sciadv.1700342. eCollection 2017 Jul.
High thermal conductivity is critical for many applications of polymers (for example, packaging of light-emitting diodes), in which heat must be dissipated efficiently to maintain the functionality and reliability of a system. Whereas uniaxially extended chain morphology has been shown to significantly enhance thermal conductivity in individual polymer chains and fibers, bulk polymers with coiled and entangled chains have low thermal conductivities (0.1 to 0.4 W m K). We demonstrate that systematic ionization of a weak anionic polyelectrolyte, polyacrylic acid (PAA), resulting in extended and stiffened polymer chains with superior packing, can significantly enhance its thermal conductivity. Cross-plane thermal conductivity in spin-cast amorphous films steadily grows with PAA degree of ionization, reaching up to ~1.2 W m K, which is on par with that of glass and about six times higher than that of most amorphous polymers, suggesting a new unexplored molecular engineering strategy to achieve high thermal conductivities in amorphous bulk polymers.
高导热性对于聚合物的许多应用（例如发光二极管的封装）至关重要，在这些应用中，必须有效地散热以维持系统的功能和可靠性。虽然单轴延伸链形态已被证明能显著提高单个聚合物链和纤维的热导率，但具有卷曲和缠结链的本体聚合物的热导率较低（0.1至0.4 W m⁻¹ K⁻¹）。我们证明，对弱阴离子聚电解质聚丙烯酸（PAA）进行系统电离，可使聚合物链伸展并变硬，堆积更优，从而显著提高其热导率。旋涂非晶薄膜中的面外热导率随PAA电离度稳步增长，最高可达约1.2 W m⁻¹ K⁻¹，与玻璃相当，比大多数非晶聚合物高约六倍，这表明一种新的未被探索的分子工程策略，可在非晶本体聚合物中实现高导热性。
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